December p MICROPHONE SURVEY SYNTHETIC STEREO REVERBERATION STUDIO MICROPHONES COMPARED. studio sound

Transcription

1 December p MICPHE SUVEY SYTHETIC STEE EVEBEATI STUDI MICPHES CMPAED studio sound

2 Highest ttinble technicl performnce QUICK AD EASY o mjor repir fcilities vilble? This professionl tpe recording equipment needs none nd cn be used with confidence nywhere in the world. In the pst fult in sophisticted equipment could men expensive down time, but in the E200 ny fult cn be quickly isolted nd the prt or circuit replced. All mjor mechnicl components nd sub -ssemblies re quickly nd esily chnged. Mny circuits simply plug -in. LEEVES-ICH EQUIPMET LIMITED A Member of the MCP Group Contct ick ichols t our London] office, telephone or Telex He will be gld to help. LEEVES -ICH EQUIPMET LTD., 319 TIITY AD, WADSWTH, LD SWI8 IYQ

3 Hmpsted High Fidelity for the highest qulity microphones STC Professionl prtners 4038 BIDIECTIAL ibbon 30 Hz - 15 khz Impednce: 3052, or 3002 utput: -80 db ref. IV t MIDIECTIAL Moving coil 40 Hz -12kHz Impednce: 302 utput: -80 db ref. IV /dyne /cm" 4104 BADCAST QUALITY CMMETAT'S ISE CACELLIG LIP MICPHE Sensitivity -84 db ref. IV Impednce 30 or 3005, ii 4037 A & C MIDIECTIAL Moving coil Frequency response: 30 Hz - 12 khz Sensitivity: -84 db ref IV Suitble for interviewing MAI STC DISTIBUTS J HAMPSTEAD HIGH FIDELITY 91 Heth Street, Hmpsted, London W3 6SS Telephones: nd LIGHTWEIGHT STUDI MVIG CIL HEADPHES mnidirectionl Frequency esponse 50 Hz to 15,000 Hz Impednce: 3002 per erphone Sensitivity --45d B ref V /dyne /cm' Weight 11 oz. (300 g.) Professionl terms vilble 607

4 Heco P the professionl one. SPECIFICATI Frequency esponse: 20-25,000 Hz. Power Hndling: 60 wtts MS. Impednce: 8 ohms. Cross -over Frequency: 250/800/3,000 Hz. Speker Assembly: ne 12" woofer. ne 5" mid -rnge speker. ne upper mid -rnge hemispheric dome rditor. ne ultr -high hemispheric dome rditor. ecommended etil Price: in Tek in white. Stnd extr. 1 Plese send me full colour literture nd test reports' on Heco Spekers. AME I ADDESS.. 1 Send to: Dept.'SS, Acoustico Enterprises Ltd, 6-8 Union Street, Kingston- upon -Thmes, Surrey Tel: /3 (3 lines) EMIIMMMIEMIIIIIMIMIMEMMM It's bck gin! ]nce gin this top qulity recording tpe is coming in from the USA nd is being mde vilble t price ll cn fford. Do not confuse SHAMCK Ferro - Sheen with chep tpe, it is qulity product mde by AMPEX, Americ's lrgest producer of high qulity tpes for industril, entertinment nd domestic use. ge Prnrock FE -SHEE PLYESTE BASE recording tpe Shmrock recording tpe TP QUALITY AT THE LWEST PICE SHAMCK Ferro -Sheen hs lwys been difficult to get, over here, but with specil rrngement with AMPEX G.B., our continuity of supplies is ssured. SHAMCKTerro -Sheen is superior product. THE GEATEST VALUE I ECDIG TAPE You get more good clen sound for your money with SHAMCK Ferro -Sheen thn with ny other tpe nywhere ner the price... SHAMCK Ferro -Sheen is extensively used by Eductionl Authorities, Universities, Lnguge Lbortories nd Tpe ecording Clubs. 608 SHAMCK Ferro -Sheen recording tpe is vilble only on 7" reels. 1800ft L.P. 75p per reel,3 for: for 4.45, 12 for ft D.P per reel, 3 for 3.40, 6 for 6.85, 12 for P & P is 5p PE EEL on ll orders under 5. PST THIS CUP T DAY Music Tpes Mil rder, 36 High Street, Slisbury, Wilts. Plese mil to me t the ddress below, the following reels of Shmrock Ferro -Sheen recording tpe. 7" 7" I enclose 5p per reel for P & P if my order totls less thn 5. me Address

5 LEVEL CTL EQUIPMET Plnning Studio... e- equipping... Expnding? AUDI & DESIG ECDIG hs lwys specilised in the field of level control equipment. We re told tht we introduced the first commercilly vilble FET Limiter bck in Well tht my be of interest to the historins, but we've relly been too busy being future orientted to notice. But it is true tht from this inception, nd with the experience gined over the yers, hs evolved rnge of over twenty units. ur products re to be found world -wide competing with the estblished gints; our units hve chieved reputtion for high qulity nd relibility (we still come cross some of our originl units functioning well fter seven trouble free yers). In this industry where time is money in very rel sense we ll pprecite the vlue of relibility. As smll compny we re ble to respond quickly to new customer requirements nd to mintin quick delivery on our stndrd rnge of rck nd modulr units. MUSIC -VICE ATI CTL -'VICE- VE': With the incresing demnd for brodcsting nd qulity P.A. network instlltions the F690 -V unit will be of interest. It provides utomtic monitoring nd mintennce of pre- determined 'Music-Voice' rtio s well s enbling 'Voice -ver' nd 'Ducking' effects to be chieved by design. Should n opertor fil to fde music chnnel in order to mintin dequte intelligibility prior to mking n nnouncement, the F690 reduces the music to the pre -set level to mintin proper blnce. ecovery to previous level is vrible from 0.1 sec. The unit only opertes to ttenute by the mount the music is exceeding the voice operted threshold. Thus music fded below the level is not further ttenuted s in mny ducking systems. When not being 'voice controlled' the unit lso cts s conventionl limiter with high threshold level under norml progrmme conditions. DE- ESSIG: Sibilnts hve lwys been problem with the film industry nd they re pprently still something of problem for the recording studio. ne cn of course use notch filters in the udio signl but this invribly colours the sound nd frequency response is permnently effected. ecent experiments with film studio hs led to the introduction of the F700 - /DS. This unit is stndrd compressor - limiter with six position peking equliser in the side -chin. Frequencies covered rnge from 4-10kHz with 20db mplitude control. Sibilnts re thus dynmiclly ttenuted without unduly ffecting the reminder of the progrmme mteril. The unit lso hs tow position low -pss 12db /oct filter. Stndrd units cn be supplied to enble unity gin equliser (such s our E -800) to be inserted in the side- chin. STEE ACK UITS re vilble nd provide both gnged nd independent ttenutors (input /output). Chnnels cn be used independently without cross -tlk problems. QUADAPHIC & STEE MATCHIG: We hve lwys given specil ttention to the proper opertion of compressor- limiters on stereo signls. It is vitlly importnt tht units re control -voltge linked nd tht the trcking of ech gin reduction element be identicl over the required rnge of compression. The use of unlinked or linked unmtched units will certinly produce imge shift if used to ny extent. We re now ble to extend the stereo mtching service to provide four chnnel mtching for Qudrphonic use (F700 -F760 Series). LW LEVEL EXPASI: With the introduction of multitrck techniques nd with the incresing desire of the Blnce Engineer to 'keep his options open', compression on reduction is to be preferred opertionlly. With the considerble mounts of compression used on live signl this nturlly tends to introduce tpe noise when done on reduction. oise -gtes hve not proved populr with engineers due to their 'on -off' chrcteristics, but by using 'softer' expnsion slope strting t 2:1 nd getting 'tighter' s level reduces it should be possible to mintin the excellent signl -noise rtio now possible on tpe. Thus with no signl present the compressor will be ttenuting in excess of 20db nd compensting for noise degrdtion tht would be cused by over 20db compression. An expnder mplifier crd will be shortly vilble for ddition to existing F700 -F760 Series units. EQUALISATI: We produce number of equliser units including the E800 'curve bender' nd other units for generl nd specilised use. A 'double notch' filter is vilble for removing 50 nd 100Hz without gretly ffecting low frequency blnce. It is lso djustble for 60 nd 120Hz. - THE r;;:u=: EW F760 PEAK LIMITE -CMPESS provides vrious compression rtios from 2:1 to 16:1 (ll ccurtely mintined between units) with switchble ttck nd relese controls (n utomtic multiple relese position is included). A seprte Pek Limiter opertes bove the compressor nd cn be djusted by 6db reltive to the compressor slopes. It is possible to use slow compressor ttck times relying on the Pek Limiter to hndle trnscients. This is useful in obtining high men levels on certin musicl instruments. IF YU HAVE PBLEMS in this field we'd like to her of them -we my well hve the nswers. Experience, qulity nd vilbility ll t the right price AUDI & DESIG (ECDIG) LTD St Michels, Shinfield od, Shinfield Green, eding, Berks. Tel: (eding) Enquiries from verses Agents welcomed: We re represented in Belgium, Brzil, Frnce, Germny, Greece, Hollnd, Itly, Isrel, ew Zelnd nd South Afric. 609

6 EW Bring'you professionl qulity on budget!.e.vbg IMF EFEECE STADAD Studio Monitor Spekers.E.W. hve been ppointed exclusive U.K. Distributors for the top IMF Monitor Loudspeker. This Speker hs previously been reserved specificlly for criticl professionl mrkets. It fetures improved low frequency stbility nd incresed power hndling cpcity. Send for detiled specifictions. Ferrogrph TAPE ECDES W DEMSTATI ew models with built -in Dolby System, vilble from stock. ALS -the superltive new Ferrogrph Speker t Chring Cross od Showrooms now. evox SPECIAL FFES evox List Price evox 1122'4. List Price evox List Price Shure, Beyer, AKG MICPHES ACUSTIC ESEACH LUDSPEAKES Come nd her ll the models from this fmous Americn Mnufcturer in our new Professionl Showroom. These Spekers re eqully suitble for studio monitoring or top Hi -Fi systems. For limited period,.e.w. re offering the following models in the renowned evox rnge t substntil reductions. H.P. terms vilble..e.w. Csh Price E E.W. Csh Price E E.W. Csh Price Ask our dvice on the model to suit your requirements from 5) these fmous mkes. ver 150 microphones in stock, from 7 to 170. Also boom rms, stnds, windshields, etc. CALEC CDESE HEADPHES MICPHES.E.W. cn meet your hedphone requirements MIXES Idel for recording or with the minimum of difficulty. Just consult We now hve in stock P.A. work, these micro- our experts on their limited supply of the phones hve virtully no recommendtions from Sony MX 12 nd Uher feedbck nd re prcti- rnge of over 20 A 121 in our rnge of less i u -' different types crried in expensive mixers. Also clly unbrekble in stock. Prices from E4 vilble, mixers in the norml use. to E69. higher price brcket. MI =MIME E.W AUDII VISUAL 1 1 IPFESSIAL SHWMS: S. LD SHWMS: Chring Cross od, London W.C UpperTooung d., LondonS.W 17 ITelephone: Telephone: /2 nd Plese send me full detils of your services 1 AME 1 I ADDESS ' 610 APLL ELECTICS We proudly introduce our complete rnge of eleven Plug -in Units for Professionl Sound Mixing Consoles. A gret del of reserch hs gone into the development of this rnge,to bring you equipment of the highest qulity nd flexibility t very resonble cost. ;. MA80 Microphone Amplifier PEI6 Presence Equliser CL36 Compressor- Limiter MI12 12in /I utput Mixer EPF4 Echo /Pn - pot /Fold bck LA26 Line -out Amplifier PAI TB90 M P62 SGS6 PS24 Electronics housed in specilly designed, very rigid cstings. ot just pretty fce! Monitor Amplifier Tlkbck Amplifier Mgnetic P -U Amplifier Test scilltor Stbiliser Power Supply And they re ll quiet! 96 MILL LAE, LD.W.6 Telephone: High speed, high qulity cssette nd reel to reel duplicting AUDIICS 160 Ewell d Surbiton Surrey Tel: STUDI ISTALLATIS T. B. Technicl, Audio Systems Consultnts, cn provide engineers for plnning, instlltion, nd mintennce of ll professionl udio equipment. Also Audio Test Equipment Hire T. B. TECHICAL LTD 38 HEEFD AD, LD, W

7 ALICE MAKES MIXES QUIET ALICE SM2 CS This mixer hs noise level of 147 db below input *. The impossible is chieved by building in CS unit. This Crosstlk nd oise Suppressor processes the udio signl by suppressing low level components in frequency selective mnner. f... This modulr CS mesures 6" by 3.6" nd hs 9 db, 14 db nd 22 db suppression cpbility. The electronics feture integrted circuits nd individul voltge stbilistion. Functions re elimintion of studio crosstlk,. removl of line or mplifier noise, elimintion of print- through nd reduction of studio reverb. time. I! Price 93 ech or 390 for 4 units rck mounted nd self powered. ALICE (Stncoil Ltd) 15 SHEET STEET, WIDS WIDS *50 Hz -I5 khz bndwidth, input 200 ohms, suppression 20:dB. 611

8 Even with perfect pickup, the distortion from grmophone record for sounds of equl level increses very rpidly t high frequencies, eventully doubling for every mjor third increse in pitch. There comes point when, to musicl ers, the distortion is incresing fster thn the musicl qulity. The QUAD filter system is designed to enble those with ers to her to obtin more of the music nd less of the distortion. QUAD for the closest pproch to the originl sound Send postcrd for illustrted leflet to Dept. S.S.T.. Acousticl Mnufcturing Co. Ltd., Huntingdon, Tel: (0480) QUAD is egistered Trde Mrk. 617

9 FEATUE ATICLES 625 MICPHE SUVEY 632 SYTHETIC STEE EVEBEATI Prt ne By Michel Gerzon 637 MICPHES By John Fisher 643 CMPAIS: STUDI MICPHES By Angus McKenzie 649 KEY EVEETT -DISC JCKEY EXTADIAY By Adrin Hope studio sound ICPATIG TAPE ECDE DECEMBE 1971 VLUME 13 UMBE 12 EDIT DAVID KIK ADVETISEMET MAAGE BI WELLS CSULTIG EDIT JH CABBE ASSISTAT ADVETISEMET MAAGE TY EWMA EGULA CLUMS 614 PECIS 614 LETTES 618 PATETS EVIEW 623 STUDI DIAY 631 AUD THE STUDIS By Keith Wicks 656 IDEX T VLUME 13 EQUIPMET EVIEWS 651 KEITH MKS MICPHE STADS By John Shuttleworth Editoril nd Advertising ffices: LIK HUSE, DIGWALL AVEUE, CYD C9 2TA. Telephone: Link House Publictions Ltd All rights reserved. HW D you test microphone? Come to tht, how do you test nything? Usully by comprison with other microphones, other crs, other doughnuts, in the sme price ctegory. In this issue, Angus McKenzie hs contributed wht my be the most comprehensive comprison of studio microphones ever published. His tests leve only one mjor question unnswered: how do these units stnd up to the buffeting of dily life? Most one -mn opertors tke prticulr cre of their recording equipment; few cn fford to do otherwise. But the pprtus put out by lrger studios is vulnerble to ccidents or mishndling. In this sitution, robust dependbility is of greter prcticl vlue thn n impressive specifiction. A microphone submitted for exmintion to Tyne Tees Television hs to survive few flls before the stff will even consider using it. All very prcticl but try telling reviewer to thump his precious C24. You re politely told where to go. Future microphone reviews, provided we cn obtin the mkers' uthority, will include stndrd shock test showing the effect of specified fll on the mesured performnce. If mker does not permit this (the equipment usully comes on lon so it is the supplier's prerogtive), note to tht effect will be included in the review. It is generl filing mong reviewers -prticulrly of domestic hi -fi products -tht routine bench tests re purveyed s complete reviews when in fct they omit ll the prcticl problems fcing the unfortunte buyer. Bench mesurements re insufficient. You hve to use product to discover its weknesses: the preselectors which brek down fter month, the tuning dil tht flips its loop, the fuses tht blow on ech climx, the ynkee mins socket with 50 kg grip. In this journl, we hve occsionlly supplemented reviews with field trils intended purely to uncover hndling problems. This hs been unstisfctory since much of the vlue of prcticl tests is lost when they re viewed in isoltion from routine performnce mesurements. Future STUDI SUD reviews will be structured on bsis combining both spects of equipment testing. 613 SUBSCIPTI ATES Annul UK subscription rte for STUDI SUD is 3 (overses 3.30, $8 or equivlent). ur ssocite publiction Hi -Fi ews costs 3.12 (overses 3.66, $8.64 or equivlent). Six month home subscriptions re 1.50 (STUDI SUD) nd 1 56 (Hi -Fi ews). STUDI SUD is published on the 14th of the preceding month unless tht dte flls on Sundy, when it ppers on the Sturdy. BIDES Loose -lef binders for nnul volumes of STUDI SUD re vilble from Modern Bookbinders, Chdwick Street, Blckburn, Lncshire. Plese quote the volume number or dte when ordering. CESPDECE AD ATICLES All STUDI SUD correspondence should be sent to the ddress printed on this pge. Technicl queries should be concise nd must include stmped ddressed envelope. Mtters relting to more thn one deprtment should occupy seprte sheets of pper or dely will occur in replying. Articles or suggestions for fetures on ll spects of communictions engineering nd music will be received symptheticlly. Mnuscripts should be typed or clerly hndwritten nd submitted with rough drwings when pproprite. We re hppy to dvise potentil uthors on mtters of style. Pyment is negotited on cceptnce

10 Precis ATICLES PICIPAUX 625 EXPSE SU LES MICPHES 632 EPECUSSI SYTHETIQUE STEE Première prtie Pr Michél Gerzon Une nlyse des diverses méthodes employées jusqu'à présent pour créer une répercution rtificielle. 637 MICPHES Pr John Fisher 643 CMPAAIS: MICPHES DE STUDI Pr Angus McKenzie Les résultts comprtifs de plusieurs fmeux microphones à condensteur, rubn et bobine roulnte. 649 KEY EVEETT Pr Adrin Hope UBIQUES EGULIEES 614 LETTES 618 EVUE DE FABICATIS BEVETEES Pr Adrin Hope 623 JUAL DES STUDIS 631 A L'ETU DES STUDIS Pr Keith Wicks 656 IDEX DU LIVE 13 EVUE D'EQUIPMET 651 KEITH MKS PIEDS DE MICPHES Pr John Shuttleworth SPEZIALATIKEL 625 MIKPH- UDSCHAU 632 KUSTLICHE KLAGWIDEHALL Erster Teil Von Michel Gerzon Eine nlyse verschiedener bisher ngewndter methoden zur erzeugung künstlichen widerhlls 637 MIKPHE Von John Fisher 643 VEGLEICH: STUDI- MIKPHE Von Angus McKenzie Einleistungsvergleich zwischen merheren beknnten kondenstor -, bnd- und drehspul-mikrophonen 649 KEY EVEETT Von Adrin Hope STADIGE UBIKE 614 BIEFE 618 PATET UDSCHAU Von Adrin Hope 623 STUDI TAGEBUCH 631 V STUDI ZU STUDI Von Keith Wicks 656 VEZEICHIS ZU BAD 13 UDSCHAU 651 KEITH MKS MIKPHSTADE Von John Shuttleworth ATICULS SELECCIADS 625 EXAME DEL MICÓF 632 EVEBEACI DEL ESTEI SITETIC Prte Primer Por Michel Gerzon Un nálisis de los vrios métodos empledos hst hor pr crer un reverberción rtificil. El utor psrá, en su segundo rticulo, sistems purmente electronicos 637 MICFS Por John Fisher 643 CMPAACI:ESTUDI MICFS Por Angus McKenzie Comprción en l ejecución de lgunos bien conocidos micrófonos condensdor cint y bobin movil 649 KEY EVEETT Por Adrin Hope ATICULS DE SEIE 614 CATAS 618 CICA DE PATETES Por Adrin Hope 623 DIAI DE LS ESTUDIS 631 ALDED DE LS ESTUDIS Por Keith Wicks 656 IDICE AL VLUME 13 CICA DE EQUIP 651 KEITH MKS SPPTES DE MICFS Por John Shuttleworth ATICLI SPECIALI 625 ASSEGA DEI MICFI 632 IVEBEAZIE STEE SITETICA Prte prim Di Michel Gerzon Anlisi dei vri metodi finor usti per crere l riverberzione rticificile. 637 MICFI Di John Fisher 643 CFTI: MICFI DI STUDI Di Angus McKenzie Vengono confrontte le crtteristische di molti noti microfoni elettrosttici, nstro e bobin mobile 649 KEY EVEETT Di Adrin Hope ATICLI EGLAI 614 LETTEE 618 IVISTA DEI BEVETTI Di Adrin Hope 623 DIA DI STUDI 631 I GII PE GLI STUDI Di Keith Wicks 656 IDICE DEL VLUME 13 IVISTA 651 KEITH MKS CAVALLETTI DEI MICFI Di John Shuttleworth Leiters 1 The Kellr review Der Sir, I wish to cll your ttention to the considerble number of errors in method, errors of fct nd mistken ssumptions published in the guise of review of the Kellr KDB1 in the September issue of STUDI SUD. The rticle is, in fct, so confusing ptchwork, nd such ides s it contins re so difficult to extrct tht simple list of mistkes must suffice here. Except nother by the sme uthor, 1 cnnot recll so unfir tretment of product submitted for review. It is lso possible tht the reviewer is ctully quite fir, in which cse it must then be ssumed tht he is eqully incompetent. 1. In the second prgrph input level controls re mentioned, nd their use is discussed lter in the review. Hving written these erlier prts of his mnuscript, the uthor complins of the difficulty of using the unit becuse no such input level controls re provided. If the 614 controls were in some wy difficult to use in opertion this is wht should hve been sid. 2. Since the Wollensk recorder loned did not ffect the input level problems, s the reviewer pointed out, the introduction of the Dolby nme is entirely grtuitous. The sme, in fct, my be sid of the repeted cittion of the mnufcturers whose mplifiers nd loudspekers re used. It is to be ssumed tht the reviewer is (continued on pge 616)

11 Telex tpe duplicting systems consist of the open reel series nd the reel to cssette series 235 CS -I. Both systems re designed for mss production of professionl qulity tpes by commercil, eductionl, institutionl, or industril fcilities. Hevy duty tpe trnsports mtd ed to solid stte modulr electronics, provide long term equipment relibility. With mixture of reel to red nd cssette modules, totl flexibility is possible. The Telex udio comprtor is the idel unit for the listen- respond -compre' lerning sitution, especilly for foreign lnguge, speech, drm, nd music studies. Pre -recorded progrmmes re plyed vi mster trck which cnnot be ersed. Student response is recorded on second -trck which my be plyed or re- recorded s required. Ech chnnel hs seprte volume controls with the students' record chnnel controlled vi mnul or utomtic control of volume. Avcom Sonifex crtridge units with Viking trnsports re designed to tke stndrd AB crtridges, type A, B & C, for continuous loop opertion. Avilble for rck -mounting or free stnding pplictions, in record /plybck /cue, plybck /cue nd plybck only versions. Prices from : Prices from : ec C1, Prices from : TELEX, AVCM Telephone for further detils nd informtion on Telex crtridges nd bulk supplies of compct cssettes. SYSTEMS LIMITED ewton Works, Stnlke Mews, LD W12 7HA SIFEX EQUIPMET..e.:0..10 '.,.rvl..z c. 93 STAWELL WAY WELLIGBUGH Telephone edwells 2142 * Portble six chnnel monophonic studio mixer type BI000 * Amplifier ssemblies providing microphone to line mplifiction, equlistion, virtul erth mixing, nd high level output functions. * Studio intercommuniction units nd systems designed nd mnufctured to specific requirements. * Brodcst type jckfield ssemblies. * Specilised sound equipment designed nd mnufctured to individul requirements. CW ITEATIAL Gme DI50 DUAL AMPLIFIE CHAEL The D150 offers ultr -low distortion mplifiction for Studio Monitor pplictions. Preset level controls re mounted on the rer pnel wy from knob twiddlers. Being 'little brother' of the fmous DC300 little need be sid beyond reminding you tht if your requirement is for the clenest Bss, the highest Dmping Fctor, the lowest oise level, nd the confidence of hving full three yer wrrnty covering ll prts then only Crown Interntionl will fulfil your needs. Freq. esponse: _- I db 5Hz to 20,000Hz t full power Power utput: (per chnnel) 180 wtts MS into 4 ohms 100 wtts MS into 8 ohms 59 wtts MS into 16 ohms I.M. Distortion: Below 0.02% Hum & oise: Better thn 110 db below 75 wtts (Typiclly 119 db) Dmping Fctor: Greter thn 200 Dimensions: 17ín wide, 54-in high, 81in deep. ck mount vilble. Full detils from sole gents: MACIES LABATIES LIMITED 71 kley od, Chinnor, xon. Tel. Kingston Blount S

12 LETTES continued employing test equipment nd listening pprtus which hve been thoroughly checked nd re ccurte in performnce. Why, then, constntly provide us with these brnd nmes? 3. It is not ssumed, s the reviewer sttes, tht `the noise which relly mtters is generlly confined to high frequencies'. This pprently innocent suggestion tht n ssumption hs been mde somewhere overlooks the fct tht estblished stndrds of noise mesurement exist in the form of DI nd AB weighting networks. These stndrds re not the ssumption of ny individul or orgniztion, nd must be used to ccurtely mesure noise reduction with ny psycho coustic significnce. This ignornce is mnifested gin when the uthor nnounces 5 db reduction in noise by the use of the KDB1 nd mesures wide bnd noise. It is lso importnt for him to understnd tht lmost ll of the noise, i.e. high frequency noise, in good tpe recorder is due to the tpe, while hum nd flicker noise re removble by good circuit design. 4. After observing tht `high level signls re unltered' the uthor lter ttempts to determine the distortion in the system t high level, 4 khz t 10 vu. As it hppens there is bout 11- db of noise reduction to be obtined under these conditions. However, testing under these conditions hrdly discloses the fcts of system opertion other thn distortion of the entire chin. In fct, the wy in which the mesurement ws mde, nd the fct tht the uthor finds it necessry to 'discover' n effect responsible for null result of n experimentl test would be musing in different context. There is no reson to ssume tht distortion hs been observed, when so mny other fctors re involved. 5. A smll point. In describing the set -up procedure, it is indicted tht the Dolby level tpe is supplemented by the use of virgin tpe. This is bit of pedntic nonsense. We re quite hppy to suggest tht the blnk tpe used need not be virgin provided tht it is clen. 6. Although the unit ws tested with three hed tpe recorder, it ws not pointed out tht the set -up procedure is in fct simpler nd fster with such mchine thn with typicl cssette recorder. 7. o line up tpe is provided for 38 cm /s becuse the 19 cm /s tpe supplied is usble t the high speed s well s t the lower speed of 9.5 cm /s. Agin, t the very beginning of the review, hd the uthor considered it, he would hve found tht Dolby level is defined s level of mgnetic flux on the tpe nd tht this is independent of speed. The first listening test described ws done, we re told, 'with tone controls flt'. Despite the highly fvourble comments bout the Dolby system mde by the reviewer with regrd to this test, we re moved to sk whether ny ttempt ws mde to estblish the system frequency response prior to judging the qulity of the results. It is prticulrly importnt becuse of the observed lck of brightness, which could hve been due to the loud -spekers, the tpe recorder, or to the chrcteristics of the pickup crtridge used to ply the discs. It is hrdly of vlue to subsequently mention the brnd of equipment used unless some reson for the choice of such equipment is given. It is even more mysterious to discover tht the Sony recorder with which the test begn ws discrded without explntion nd the Wollensk substituted. Since the Sony is vilble in the UK nd the Wollensk is not, would not the Sony hve provided more relevnt test? The reviewer sttes tht ttempts t mesuring distortion `fil to produce ny evidence of incresed distortion' except for reding of 0.5 per cent under conditions which, the uthor fils to disclose, represents the highest distortion point of the Kellr circuit. The question is then rised, but typiclly left unnswered, s to whether the reviewer hs discovered `Dolby B Achilles Heel'. The Dolby circuit itself cn be designed to hve rbitrrily low levels of distortion. n pge 481 of the sme issue of STUDI SUD, more complex version of the sme circuit -the Dolby Lbortories professionl model 320 -is shown to hve distortion `lower thn 0.01 per cent' under conditions similr to those in the review under discussion. So much for Achilles. 8. The uthor of the review hs decided tht `properly set -up recorders t 19 cm /s should not need Dolby for norml recording purposes'. This informtion will be of inestimble vlue to the hundreds of professionl studios which hve purchsed thousnds of units for use t even higher speeds thn 19 cm /s. The further observtion by the reviewer tht the KDB1 `produced no udible effect t this speed' contrdicts the evidence of mny demonstrtions nd experiments crried out with ll types of equipment. Incidentlly mong those rriving t opposite conclusions from the reviewer is the mnufcturer of the tpe recorder used in the test. ne cn only wonder whether the reviewer would hve considered it resonble to mke pino recording nd ply tht bck t levels which were 'relistic', the term which he used to describe the listening levels he employed. There is hrdly tpe which will not disclose n unplesnt bckground noise when the pino is reproduced on relistic levels tht is, the levels which would be obtined with pino in the listening room. Moreover, the excellent qulity of the recorder used in the open reel tests is irrelevnt, becuse the noise level obtined in most recordings is lmost ll due to the tpe, not the recorder. 9. Why does the uthor perversely suggest tht t 19 cm /s 'the Dolby might be of use in mking multi -genertion copies' if, s he immeditely observes, 'it is difficult to imgine why nyone should choose to do his recordings in this wy' The frequency response tests mde on the Wollensk re only test of the system, nd tell us nothing bout whether or not the Dolby System is operting properly. 11. The complete hypotheticl distortion of 0.3 per cent which the reviewer clcultes, would represent the level of 60 db, well below the level of the tpe noise. Without wishing to concede for moment tht the distortion exists, should it not hve been pointed out tht it is not only `insignificnt' nd `mply compensted' but lso totlly inudible? 12. Although the meters on the KDB1 were mrked in vu units on erly production, they were only intended for use in clibrtion nd not for monitoring recording level. The comprisons to the meters on the recorders re therefore meningless. 13. The reviewer once gin gives us n expert listening pnel to ssist with his review, which in this cse unnimously prefers non -Dolby recordings. This is lter ttributed to devitions of few dbs t 20 or 30 db below 0, these sme devitions occurring minly between 4 nd 14 khz. First, we should congrtulte the nonymous pnel on its remrkble hering. But now tht this unique preference hs been discovered, ws it lso investigted t other speeds, with other equipment, nd with other such stute listening pnels? It is not only tht the numerous other errors in the review shke one's confidence in the reviewer's bility to crry out such test competently; it is lso necessry to consider tht it contrdicts ll previous experience in the use of the Dolby B system with properly operted equipment. It my seem unusul to tke reviewer to tsk so strongly when he hs written wht is,. fter ll, fvourble (if somewht odd) review. However, it is from the publiction in journl s reputble s STUDI SUD tht uthority is loned to those whose judgement must stnd the strongest light of exmintion. Even llowing for the fct tht everyone mkes mistkes, the reviewer in question fils utterly to withstnd such exmintion. Yours fithfully, Sidney Lrholt, Director, Kellr Electronics Ltd, 6 Bycullh Avenue, Middlesex. I cnnot understnd why Mr Lrholt's letter ws written; the substnce of my review ws given to Kellr Electronics nd Dolby Lbs for their comments before publiction nd ll his points could hve been rised then. Kellr's only rection t the time ws tht they thought the review very fir. [Dolby commented on number of detils in the review but, due to n dministrtive error, severl suggested chnges were not mde -Ed.] I will, however, ttempt to stisfy Mr Lrholt over some of his points. I. It ws pointed out in the review tht the output from the Sony overloded the inputs, nd I ssume tht reders of this journl would be wre of the symptoms. I did not stte tht no input level controls were provided but suggested tht, if ttenutors such s those mde up for use in the review were incorported in the KDB I, the input controls provided would then be of use. (continued on pge 618)

13 udio Engineering for Professionls Four yers go, only hndful of people hd herd of the Millbnk Electronics Group. Tody, our equipment is operting in 25 countries nd is specified by most mjor professionl users of udio nd communictions equipment in the United Kingdom. Why? We think the simple nswer is tht we give our customers exctly wht they wnt. When Millbnk Electronics ws formed, but before it strted to mke nything, we took the trouble to tlk to people with yers of prcticl knowledge nd experience of the Audio Industry. Professionl engineers. They told us exctly wht they wnted; we went wy nd mde it. And tht's precisely wht we've been doing ever since. Everything we mke undergoes stringent qulity control nd is subjected to vigorous test procedures before it is pssed for desptch (things like this hve helped us to win the pprovl of the Cndin Stndrds Assocition). Tke, for exmple, our rnge of sound mixers. At the moment there re four bsic types designed to suit wide rnge of pplictions. The MCC Mrk II illustrted bove is n eight chnnel sound mixer employing liner motion fders rrnged 01- in two groups of four. Ech group hs ssocited bss nd treble tone controls nd mster fder. By the use of our plug in udio modules the following inputs my be obtined: () Microphone, ny impednce from 30 to 600 ohms. (b) Liner unblnced, ny level from 20mV to 11 volts! (c) 600 ohm line (d) (e) Equlised tpe hed Equlised mgnetic crtridge Two 600 ohm floting blnced line outputs re provided nd you cn chose from either VU or PPM monitoring. Pre fde listen buttons re fitted to ech chnnel nd ech group nd 2 Wtt udio mplifier is provided for hedphone or loudspeker monitoring. There is even n output/ input socket for externl curve benders, etc., etc. Choose from Din stndrd or Cnnon termintions. Utilizing stndrd 19" rck formt, it my be rck or cse mounted. If you would like leflets nd technicl informtion on our rnge, plese telephone or write to our Generl Sles Mnger, Bernrd Skinner. EMillbnk Electronics Group, Bellbrook Estte, Uckfield, Englnd. Tel: Uckfield 4166 ( )

14 LETTES continued 5/6 2. /don't know why the use of the Dolby nme 7. nnoys Mr Lrholt -the KDB1 is mnufctured to Dolby design under licence. I mention the other equipment used for listening tests so tht reders cn judge to some extent the stndrds by which the equipment is judged. The first listening tests were crried out on equipment which ws considered resonble domestic 'budget' set up of the type for which it ws felt the KDB1 might well be suited; the second with (rgubly) the highest qulity domestic system vilble. Since the KDB1 is designed for domestic use, it seemed to me tht both these tests were vlid nd relevnt. 3. The short prgrph devoted to the design philosophy nd method of opertion of the Dolby B system ws tken direct from Dolby Lbs literture on the subject nd Mr Lrholt should tke the designers of his unit to tsk over this if he does not gree. I cnnot see wht DI nd AB weighting networks hve to do with this or whether hiss is due to tpe or tpe recorders. I cn't recll rising ny of these topics in my reviews though if the DI nd AB weighting networks re not the ssumption of ny individul or orgnistion s Mr Lrholt sttes I would be interested to her how they were designed. 4. I thought I hd mde it cler in the review tht doing this test the performnce of 8. system without nd then with the KDB1 ws being mesured nd it is obviously importnt to determine whether the KDBI hs ny effect t ll levels -fter ll the signls pss through the unit even if they re high level. I cn't comment on Mr Lrholt's remrk bout 'my ttempt to discover the effect responsible for null result of n experimentl test' except to sy tht this conjures up fscinting picture; unless by 'null result' he mens the definite 8. preference of number of experienced listeners to the non Dolbyed tpe -in my view very positive nd relevnt result even if puzzling.. Points tken, though I think we should ssume reders of this journl would be fully wre of both these. I ws sked by Kellr not to test the unit t 38 cm /s s the licence for Dolby excluded its use professionlly. The tpe provided for lining up ws not suitble for 38 cm /s becuse its length ws so short tht t tht speed it rn off the spools before one hd time to twek the controls. These points did not seem relevnt to the review so were not mentioned t the time. I thought I mde it cler in the review tht most listeners thought the sound from the tpe better thn tht from the disc, nd tht the fct tht the ltter ws `brighter' did not imply 'lck of brightness' from the tpe; these re Mr Lrholt's words not mine. I thought I hd mde it cler tht the 0.5 per cent distortion ws mesured t 1.5 khz, 15 db, but regret tht owing to n omission somewhere between my submission to the editor nd the printed version it ws not mde cler tht not only ws the distortion trced to the KDB1 nd not n error, but the form of distortion ws shown on n oscilloscope. Quoting the performnce of different instrument costing fr more thn the KDBI, designed for professionl use, nd incorporting specil circuitry to eliminte this prticulr distortion seems to me to be n unnecessry red herring nd doesn't lter the fcts. I cnnot comment on 'mny demonstrtions nd experiments' Mr Lrholt mentioned s I ws not present, I cn only report my own findings honestly nd this I hve done. The sttement mde by Mr Lrholt tht 'noise level in most recordings is lmost ll due to the tpe nd not the recorder' is complete nonsense nd bers little reltion to fct, prticulrly when domestic recorders re considered -the ones for which the KDB I is supposed to be designed. I hve often done exctly wht Mr Lrholt suggests- recorded pino nd plyed bck in the sme room t level tht mde it impossible for people stnding just outside the open door to tell whether the pino or the recording ws being plyed. Even without Dolby the noise level t this `relistic' level is insignificnt provided high qulity equipment, properly set up, is used. 9. Sorry bout this, nother chunk of my writing got missed out somewhere nd the whole sense of this prgrph ws ltered. The test originlly described showed tht 6th genertion Dolbyed copy hd bout the sme hiss level s 2nd genertion non Dolbyed copy. The remrk t the end referred to 8th genertion copies. 10. See my comments on (4). 11. Wht does `insignificnt' men to Mr Lrholt? It seems tht if he hs to gree with wht I sy he must disgree with the words 1 use. Why? 12. The remrks on the vu meters were mde becuse the instructions supplied with the KDB1 fil to give ny guidnce s to whether fter lining up one should use the KDB1 or the recorder's meter for setting levels -in fct one should use the KDBI controls nd the recorder's meters - pretty silly but I suppose necessry rrngement. 13. If Mr Lrholt cn't her the difference ' few dbs minly between 4 nd 14 khz' mde to signl he should employ some younger ers to help. Considerble experience hs shown me tht it is surprising how few dbs re needed t this end to mke ll the difference, but fter ll I only stted 'It is possible tht slight chnge etc' nd did not 'ttribute the preference to it' s Mr Lrholt sttes. I regret being involved in yet nother exchnge with mnufcturer over review, but I suppose tht unless my reviews re to be innocuous nd meningless I must expect thisoccsionlly. Ionly hope tht others red my reviews with more cre nd in more generous spirit thn Mr Lrholt. However, ll this does not lter the fct tht if you hven't noise problem you don't need KDBI but if you hve nd prticulrly if it is HF noise then the KDBI is for you nd is good vlue for money, but it is not mgic cure -ll for other recording fults, nd I hope I mde this cler in my review. John Shuttleworth Pdtents eview BY ADIA HPE DYA Mgnetic Devices hve new ptent BP 1,237,566 for Inertil ection Trnsducers. Although t first sight these my not seem too relevnt to our field, closer look suggests otherwise. In communictions systems it is often inconvenient, for one reson or nother, to hve hedphones nd mike boom or throt mike. Eqully often, something long these lines is essentil if the opertor is to hve both hnds free for other purposes. Policemen, for instnce, need their hnds free but cnnot relly crry mike boom on their helmets. Dyn hve devised trnsducer which is suitble for fitting in ht or helmet nd their little gdget ('little' is the opertive word, i.e gm weight nd 11 x 6 x 5 mm size) is usble either s microphone or receiver. It is formed from suspended weight system linked by rod to n rmture of n electromgnetic motor system. When the gdget is being used s contct mike (e.g. worn on top of the hed), the tiny vibrtions produced in the skull by speech cuse most of the motor prt of the trnsducer to vibrte while the weight nd rmture remins more or less sttionry. The 618 result is signl voltge from the motor which cn be mplified nd fed out in the usul wy. When the trnsducer is being used s receiver, udio signls re fed into the motor, which cuses the rmture rm nd weight to vibrte in typicl mnner nd, by inertil rection, the whole gdget vibrtes. As result, Dyn clim udible sounds coming from the hed top. According to the inventors, their trnsducer shows rising chrcteristic from 300 Hz to 2.4 khz with 9 db rise per octve nd stedy (continued on pge 620)

15 Snsui 4- Chnnel Stereo. the Doors Are Alwys pen. ow, wlk right in nd step right up to fbulous new experience in sound - Snsui 4- chnnel stereo. The door -both doors re lwys open. ne door gives you ccess to new building - from- scrtch 4- chnnel receivers, the other to supplementry components tht will let you up -grde your two -chnnel system to 4- chnnel sttus in seconds. Either wy, you cn instntly convert your vluble two -chnnel tpes nd records (s well s FM brodcsts) into the new formt. For those interested in complete new 4- chnnel system, the 240 wtt Snsui Q Chnnel eceiver is the idel nucleus. This truly extrordinry unit, which incorportes # 41 - the exclusive 4- chnnel synthesizer decoder, lso gives you super- sensitive stereo tuner, plus high performnce control mplifier for ll the power you'll probbly ever need. But if tht's still not enough, check out Snsui's 280 wtt Q Something more modest? Snsui's 100 wtt Q or 60 wtt Q -500 might prove to be more in line with your needs. Building on two -chnnel system? Then choose the verstile new 120 wtt QS Chnnel er Amplifier. Added to your present system, long with second pir of speker systems, it elevtes you to 4- chnnel sttus instntly. And the 50 wtt QS -100 cn do the sme. You're on the threshold of this enthrlling new 4- chnnel experience row. Stop in soon t your nerest uthorized Snsui deler nd wlk right in. Either door Snsui_ r CHAEL STEE Q Englnd: VEIT (UK) LTD. Thornhill Southmpton S09 5QF Tel: Southmpton I Irelnd: ITEATIAL TADIG GUP LTD. 5 Cope Street. Dme Street, Dublin 2 / West Germny: CMP HI -FI G.M.B.H. 6 Frnkfurt m Min, euterweg 65 / Frnce: HEI CTTE & CIE 77, ue J. -. Thorelle, 77, 92- Bourg -l- eine / Luxembourg: LUX Hi -Fi 3, rue Glesener, Luxembourg / Austri: THE VIEA HIGH FIDELITY & STEE C. A 1070 Wien 7, Burggsse 114 / Belgium: MATELECTIC S.P..L. Boulevrd Léopold II, 199, 1080 Brussels / etherlnds: TEMPF.V. Tilburg, Kpitein Httersstrt 8, Postbus 540 / Greece: ELIA LTD. 59 & 59A Tritis 5eptemvriou Street, Athens 103 / Itly: GILBET GAUDI s..s Milno, Corso Di Port uov, 48 / South Afric: GLES (PTY) LTD. P.. Box 6406 Johnnesburg / Cyprus: ELECTACUSTIC SUPPLY C., LTD., P.. Box 625, Limssol / Portugl: CETELEC LDA. Avenid Fontes Pereir de Melo, 47, 4.o dto., Lisbo -1 /Mlt:. BIZZI 293, Kingswy, Vllett /Cnry Islnds:. HASSAAM Clle l vl, 87, Ls Plms / SASUI AUDI EUPE S.A. Dicem Bldg., Vestingstrt 53-55, 2000 Antwerp, Belgium / SASUI AUDI EUPE S.A. FAKFUT FFICE 6 Frnkfurt m Min, euterweg 93, West Germny / SASUI ELECTIC C., LTD. 14-1, 2- chome, Izumi, suginmi -ku, Tokyo 168, Jpn 619

16 PATETS EVIEW CTIUED roll -off from the pek to 3.8 khz. This, they suggest, produces good speech intelligibility, good speech pick -up nd low mbient noise. The kind of not -too -obvious ppliction tht springs immeditely to mind is the possible use of this type of trnsducer in studio communictions systems -it could for instnce put n end to those occsions when drmtic moment of TV drm is deflted by live mike picking up n `ver to your right, Cmer ne' instruction escping from the hedphones of nerby crew. Ampex Corportion's BP 1,239,363 describes some improvements they re mking in the mgnetic hed ssemblies for cssette recorders. The specifiction lso provides further insight into the problems involved in cssette hed production nd some of the wys tht re used to tckle them. If cross tlk nd other bugs re to be ironed out of cssette recorders t resonble cost, highly utomted ccurte construction techniques re essentil. Ampex use hed ssembly which tpers from rer to front, i.e. gets wider wy from the tpe re, so s to provide for esier connection of the coils. The hed ssembly is formed from pir of structurlly comple- mentry Bkelite crriers. Ech of these crriers hs series of notches in its rer end nd the notches re tilored to receive the vrious pole nd core segments. As I mentioned bove, there is convergence of the hed entrils lterlly towrds the hed -to-tpe interfce nd the type of ngles involved re in the order of 10. Ampex mintin tht, by using their notched crrier system, they cn set up the hed ssemblies quickly nd ccurtely with minimum of jigs. Apprently the only jigs necessry re those required to keep the proper spcing between the tips of the trnsducers t the hed - to -tpe interfce nd to hold the notched crriers in plce. therwise the Ampex ssembly is self- supporting nd mintins everything in its proper spced reltionship until the whole thing is internlly encpsulted with insultive epoxy. Incidentlly, Ampex remrk tht their erse heds re fixed to simultneously erse Chnnels ne nd Two (nd, of course, Chnnels Three nd Four) without leving n unersed intermedite spcing. This is chieved by hving the erse trnsducers extend cross the full width of the two ssocited stereo pir trcks nd will provide more complete ersure thn in the cse where individul erse trnsducers re ssocited with ech record / plybck trnsducer. According to Ampex this type of hed ssembly will provide plybck output signl of 265 p.v t 1 khz nd cross tlk db below operting level between stereo pirs. For nyone wondering where it is ll heding, Westinghouse Brke nd Signl Co. Ltd, my hve the nswer in BP 1,236,483. In more or less their own words this ptent is for signl recording nd plybck pprtus of the type where the trnsducing hed is co- operble with one of number of longitudinl trcks on recording medium, the hed being mounted on crrige which is displceble in discrete steps by uni- selector so s to llow desired one of the trcks on the record medium. All of which is bit of mouthful. Wht it mens is tht tpe loop crries number of prllel recording trcks nd hed cn be moved cross the tpe by uniselector. Westinghouse suggest tht their invention is going to be prticulrly useful where it is wnted to record number of messges on loop of mgnetic tpe nd then pply control signls to select n pproprite messge in dependence on some condition or nother -like the wether or the stte of one's overdrft, or the system cn be used in telephone nswering systems or where ech of the trcks crries trin of pulses representing telephone number. This wy, on receipt of commnd signl, equipment will utomticlly dil preset telephone number. But Westinghouse hve nother suggestion. According to them the equipment cn be fitted t centre for supervising some unspecified thing or nother nd during periods when it is unttended by personnel, i.e. when the stff hve gone home, cn cll up outsttions nd retin messges received from the out -sttions, indictive of the sttes of gdgetry out t the outsttions. And wht hppens if the outsttions re lso unttended? Presumbly the Westinghouse gdgets will then be wsting the firm's time nd money by clling ech other up for cht when they get bored. THE FLLWIG 'ist of Complete Specifictions Accepted is quoted from the September issues of the fficil Journl (Ptents). Copies of specifictions my be purchsed t 25p ech from The Ptent ffice, rpington, Kent B5 3D. September 2 1,249,203 Interntionl ectifier Co (GB) Ltd Electric bttery chrging circuits incorporting solid stte rectifiers 1,249,221 Dwney, J. C. G. nd Fulkner, E. A. Electronic mplifier circuit rrngements 1,249,222 CA Corportion Gin controlled mplifier 1,249,236 Wilson & Longbottom Ltd Mens for winding mterils t constnt nd vrible tension nd liner velocity 1,249,251 Westinghouse Electric Corportion High relibility semiconduct ve devices nd integrted circuits 1,249,266 Fernseh GmbH Television cmer 1,249,274 Ford Motor Co Ltd Mgneticlly determining mechnicl properties of moving ferro- mgnetic mterils 1,249,310 Columbi Brodcsting System Inc Film recording method nd pprtus 1,249,360 Sony Corportion Led ssembly nd method of mking the sme 1,249,395 Bofors A.B Low frequency signl mplifier 1,249,464 Plessey Co Ltd Piezoelectric trnsducers 1,249,483 Vyzkumny Ustv Mtemtickych Strouju Arrngementfor displying nd recording hysteresis loops of ferromgnetic mterils 1,249,497 Sony Corportion Apprtus for utomticlly eliminting n influence of the erth's mgnetic field on colour television receivers 1,249,547 Telefon Aktiebolget LM Ericcsson Arrngement for indicting if periodicl signl exceeds certin frequency 1,249,557 Telettr Lbortori di Telefoni elettronic e rdio S.p.A. Device for reducing noise in the ouput wires of memory 1,249,593 Interntionl Stndrd Electric Corportion Automtic gin cmer tube 1,249,598 Generl dio Co Signl genertor pprtus control system for 1,249,686 Wurlitzer Co umericl storge phonogrph selector 1,249,696 Mttel Inc Sound reproducing pprtus 1,249,704 Mohwk Dt Sciences Corportion Hub for tpe reels nd the like 1,249,716 CA Corportion Trnsducer rrngement 1,249,755 Amp Inc Apprtus for crimping electricl connectors to wires 1,249,761 Telecommunictions dioelectriques et telephoniques Trnsmission device for the trnsmission of nlog signls by mens of pulse code modultion 1,249,762 Philips Electronic & Associted Industries Ltd Priority circuits 1,249,775 Eisen W. Trossinger Metllstimmenfbrik Hns Eisen Sound eproducing pprtus September 9 1,250,226 Interntionl Stndrd Electric Corportion Pseudo -rndom dot interlce television system 1,250,380 Phifps Electronic & Associted Industries Ltd 620 Speech controlled bidirectionl mplifier 1,250,392 Interntionl Ptente Etb Sound plybck pprtus 1,250,393 Philco -Ford Corportion Formnt frequency extrctor 1,250,397 Stempel A.G. D Sound dmping mteril nd the mnufcture thereof 1,250,416 Peripherl Systems Corpoition Mgnetic recording pprtus 1,250,430 Klostermrk B. Trnsportble coxil cble 1,250,517 Brun K. Grmophone pickups 1,250,640 ippon Gkki Seizo K.K. Loudspeker 1,250,645 Mtsushit Electric Industril Co Ltd Electron bem converging device 1,250,740 Philips Electronic & Associted Industries Ltd Television cmer tube 1,250,761 Electroube Ltd Clening elements for electricl contcts 1,250,766 SC Industrielle De Liisons Electroniques Device for detecting fults in two -wire line

17 1,250,777 Western Electric Co Phse controlled oscilltors 1,250,780 Philips Electronic & Associted Industries Ltd Device for unwinding tpe 1,250,818 CA Corportion Circuit dptble s wide bnd mplifier 1,250,821 Interntionl Computers Ltd Mgnetic printing pprtus nd mgnetic trnsfer medi 1,250,828 Fernseh G.m.b.H. Colour television rrngement September 15 1,250,919 nd 1,250,920 Western Electric Co Trnsistor oscilltor circuits 1,250,930 Stndrd Telephone Cbles Ltd Electromgnetic relys 1,250,937 Siemens A.G. Commuttor -less DC motor with Hll genertor control 1,250,967 Agf -Gevert AG Method of producing symmetrising tpe in the recording tpe technique 1,251,008 Columbi Brodcsting Systems Inc Film recording method nd pprtus 1,251,014 CKD Prh borovy Podnik Inverter circuit utilising commutting trnsformers 1,251,055 Minnesot Mining & Mfg Co Piezoelectric semiconductor coustic wve signl device 1,251,074 tionl eserch Development Corportion Frequency multiplying electricl circuits 1,251,097 Alford A. Coxil connectors 1,251,114 Collins dio Co Vrible impednce switching regultor 1,251,127 Institut Frncis Du Petrole Des Crburnts et Lubrifints Device for emitting coustic wves in wter 1,251,267 Stndrd Telephones & Cbles Ltd Wire wrpping tools 1,251,285 Philips Electronic & Associted Industries Ltd Method of mnufcturing printed circuits 1,251,308 Burroughs Corportion Mgnetic recording hed 1,251,348 Sony Corportion Semiconductor integrted circuit nd methods of mnufcturing the sme 1,251,372 cl -Thermionic Ltd Tpe recorder heds 1,251,379 CA Corportion pertionl mplifier suitble for pprtus for mesuring low voltges nd currents 1,251,382 Plessey Co Ltd ptoelectronic semiconductor devices 1,251,415 CA Corportion Tpe receptcle 1,251,417 ITT Industries Inc scilltor circuit 1,251,439 Grundig EMV Elektro- Mechnische versuchsnstlt, Inh Mx Grundig Apprtus for trnsmitting pictures over communiction chnnels of restricted bnd width 1,251,448 Western Electric Co Methods of nd pprtus for recording nd reconstituting imges of three dimensionl objects nd records produced by the recording methods 1,251,453 Mtsushit Electric Industril Co Ltd Degussing device 1,251,454 CA Corportion Integrted circuit 1,251,455 Burroughs Corportion ecord medi processing pprtus 1,251,477 Xerox Corportion Mgnetic developing pprtus for ltent electrosttic imges 1,251,497 Interntionl Business Mchines Corportion Method nd pprtus for recording colour imges 1,251,515 Jungner Instrument Method nd circuit for converting dc voltge to n c voltge 1,251,559 Sony Corportion Coblt ferrite system mgnetic powder 1,251,563 Grphic Trnsmission Systems Inc. Bndwidth reduction system 1,251,576 Siemens AG Electric pulse genertors or switches hving permnent mgnet circuit 1,251,587 Associted Electricl Industries Ltd Control methods nd rrngements for electric motors 1,251,596 Philips Electronic & Associted Industries Ltd Dc permnent mgnet motor 1,251,653 Selectro -Micro Co Ltd Imge reproducing pprtus 1,251,693 Westinghouse Electric Corportion Semiconductor integrted circuit hving mis nd bipolr trnsistor elements 1,251,706 CA Corportion Mixer Circuit September 22 1,251,837 Bosch G.m.b.H Semiconductor components 1,251,851 Guss Electrophysics Video signl trnsducer 1,251,861 Generl Electric Co Electrolytic cpcitor nd electrolyte mteril thereof 1,251,866 CA Corportion Automtic degussing circuits 1,251,888 Cterpillr Mitsubishi Ltd Method of dip -soldering 1,251,923 Polsk Akdemi uk Instytut Auto - mtyki Wveform genertor 1,251,927 Siemens AG Arrngement for generting unidirectionl voltge relted to speed of rottion 1,251,967 British Brodcsting Corportion Inter- conversion between digitl nd nlogue quntities September 29 1,252,572 tionl eserch Development Corportion Alternting current rectifier nd dc inverter circuit rrngements 1,252,574 Jyrk Instruments Corportion Projector for continuous loop motion picture 1,252,575 Jyrk Instruments Corportion Film crtridge for continuous loop motion picture film 1,252,741 Plessey Co Ltd Speech encoding systems 1,252,814 Interntionl Business Mchines Corportion Electricl pprtus exhibiting negtive resistnce 1,252,841 Furuno Electric Co Ltd System for recording electricl signl 1,252,845 Siemens AG Mgnetic disc dt stores 1,252,874 Tektronix Inc Attenutor pprtus 1,252,942 Communictions Ptents Ltd Wire brodcsting systems 1,252,987 CA Corportion Integrted power output circuit 1,253,031 Dolby.M. Signl compressors nd expnders 1,253,045 Bose Corportion Loudspeker system 1,253,256 Du Pont De emours & Co Electricl circuit for suppressing undesirble electricl signls 1,253,356 Tong. D.A. Super- regenertive oscilltor circuits 1,253,390 AGA Ab Arrngement for controlling nd indicting the phse of n oscilltion 1,253,431 Columbi Brodcsting System Method nd pprtus for opticlly recording colour picture informtion on photogrphic medium HIGHSPEED TAPE 6 CASSETTE CPYIG lrge nd smll runs Frser Pecock Assocites Limited 94 High Street Wimbledon Villge London SW AUDI CECTS BADCAST PATTE JACKFIELDS, JACKCDS PLUGS & JACKS. QUICK- DISCECT MICPHE CECTS. AMPHEL (TUCHEL) MIIATUE CECTS WITH CUPLIG UT. HISCHMA BAAA PLUGS & TEST PBES. XL CMPATIBLE I -LIE ATTEUATS. LW CST SLIDE FADES BY UF. FUTUE FILM DEVELPMETS LTD. 38 Hereford od, London W2 5AJ or

18 'lì0r..,.x-sz+st,2rzm ' "7ilie! I»!r. SAIT Feectiteftutt Z is now firmly instlled in the former B.B.C. SAIT SUD MIXES ALLTPE LIMITED 5B.Thme Industril Estte,Thme xon. Sles fficetel ECDIG STUDI " WALKE HALL " Air -conditioned studio Ample cr prk ecording cpcity for 30 musicins Plese write for new studio brochure or telephone (24 hour nswerphone) ZELLA ECDS (BIMIGHAM) LTD. " Wlker Hll," Ampton od Edgbston, Birminghm BIS 2UJ 622 Highspeed Tpe Copying Equipment f p eel to reel eel to cssette FrserPecockAssocites Limited 94 High Street Wimbledon Villge London SW sole UK distributors of Infonics WE SPECIALISE I BAD EW TP QUALITY BITISH P.V.C. MYLA & PLYESTE ECDIG TAPES WITH FITTED LEADES, Etc., EX 3" Thnks to bulk purchse we cn offer tensilised HI -FI tpes, mnufctured by British firm of world repute. All boxed individully (seled if required) in polythene. ur tpes re not to be confused with imported sub -stndrd or used tpes. Full money refund if not delighted. This month: - "DY SPLICE" (19p) given FEE with every order. Std. L.P. D.P. Boxed Length e. 3 for Length e. 3 for Length e. 3 for empty spis 3" 150' 10p 29p 3' 220' 12 =,p 35p 3" 400' 22 }p 65p 3" 3p 4" 300' 20p 50p 4" 450' 25p 70p 4" 600' 34p 97 =,p 4" 8p 5" 600' 30p 871p 5" 900' 40p E1 17 -, 5" 1200' 624p E1 85 5" 9p 5F' 900' 35p El-02f 5; "l200' 521p El 52} 5- "1800' Sp E2 S0 5e" 9p 7" 1200' 45p El.271 7" 1800' 65p El ' El S E3 05 7" 10p All orders desptched by return. Postge nd Pcking 9p per order STAMA TAPES, 421 Stines od, Bedfont, Middlesex

19 SFudio Diry BY KEITH WICKS APPLE'S new studio in Svile ow is equipped with 30/16 Helios mixer, 16 nd eight trck recorders by 3M, four nd two trck Studers, loudspekers by Telefunken, Cdc nd EMI, mplifiers by HH Electronics, Cdc nd Audix, nd microphones by eumnn, AKG, STC, nd others. everbertion is provided by EMT pltes, nd chmber reputed to hve cost 5,000 to build. The whole project cost round 500,000 nd I hope to give more detils next month. At Mrquee Studios, Colin Cldwell engineered Blck Widow lbum, produced by Mlcolm Koss for Excellency ecords. Johnny Johnson nd the Bndwgon recorded single, produced by Tony Mculey, nd Chris Brber's Irish bss plyer, Jckie Flvelle, hs just strted on single with producer Deke Arlon. Studio mnger Phil Dunne recorded Medicine Hed single nd hs just strted lying down lbum trcks for the sme group. Phil's most interesting session this month ws mobile recording t the Hmpsted Thetre Club for Principl Edwrd's Mgic Thetre. The Pye mobile unit ws hired for this job, coped dmirbly, nd ws highly prised by Phil who directed the session. `The vn is mrvellous,' he sid. 'Quite the best thing I've seen in this country. It comes complete with stff, who re bsolutely excellent. The vn drives up, ll the doors open, nd ll these people lep out nd get on with the job. The session ws quite difficult s ll the 12 musicins doubled on instruments but the stff coped well nd were so esy to work with. `The most difficult thing ws getting permis- sion to prk the vn in front of the librry, which ws the most convenient position. There ws tlk bout it being blck sphlt incpble of supporting hevy lod. It took s long to get permission to prk the vehicle s it did to record the session. I didn't get to tlk to Sir Bsil Spence, who designed the building, but I did spek to 300 Deprtments of Works. o lies, it took from 2 p.m. to 5.30 p.m. to get to the right deprtment nd then they were only worried bout where we were going to empty out our shtrys. The session itself went very well nd some of the mteril will be issued on John Peel's Dndylion lbel.' Hookey recently did n lbum of their own mteril, the producer for this being oger Wtson. The Houseshkers, revivl rock 'n roll bnd, complete with drpes nd sidebords, mde single for CA with producer Brry Bethl. Gerry Hmilton. rriving t the studio direct from horror film session, recorded single while covered in rtificil blood. o comment. The Mrquee Club, so convenient for recording live shows, ws used for Crvn session filmed by Germn television. Phil Dunne's ltest problem is how nd where to record 200 voices, 80 kzoos, ten trombones, ten french horns, ten trumpets nd n orgn. 'I'll probbly tke mobile vn long to somewhere like the Kingswy Hll when I've worked out exctly wht I'm going to do. Dvid Bedford, music techer, ws commissioned to write few numbers for Dndy - lion nd, when he told me wht he wnted to do, I thought he ws joking. But I rng the record compny, nd they confirmed the story. I ws mzed.' Fcilities re to be improved still further t Mrquee. The studio is to be extended to ccommodte nother ten musicins, more 6.25 mm tpe mchines re to be instlled, nd new phsing unit is lredy in opertion. Mde by Helios, this unit costs bout 160 nd works very well ccording to Phil Dunne, lthough he ws unble to tell me how it worked s certin prts of the circuitry hve been encpsulted. Wembley's Intersound studio hs been continuing with pop cover mteril for Pickwick. The Ann Dell Trio recorded six originl numbers, Simmsofrmi of Pris lid down more trcks, nd Dve oberts produced the Sd for Phoenix ecords. At Myfir, Pul Lynton of Acremere produced I Live In A Drem, single which could do well judging by the interest shown by number of record compnies. Eddie Sego, regulr visitor to the studio, hs been in with Mike Lender to record number of demos, nd John Drummond produced some four trck demos for Mrtin -Coulter Enterprises. At lest, they strted off s demos with hlf dozen session musicins on one trck nd voices on the other trcks but the results were so good tht the demo becme mster. Myfir hope to enlrge their studio nd control room in the not too distnt future nd will probbly instll ir conditioning, Dolbys, new spekers, mplifiers nd limiters, s well s their new control desk. Engineers Dve Mynerd nd John Hudson re in the process of building some equlisers bsed on new concept. These pprently do (continued overlef) 623 Dve Hdfield t Mximum's new 16 trck Scully.

20 r I I I I I I I I I I I I I I I I I I I I I I I STUDI DIAY continued wht you would expect them to do, but better. John dded n ir of mystery to the project when he told me tht the units would not be mrked in the usul wy with bss, treble, boost, nd cut. `They re going to be mrked with words nobody hs ever used before.' The mind boggles. Assuming ll goes well when these equlisers re tried out, they my well be put on the mrket. You my recll tht Dve nd John recently built desk for Dublin's Trend Studios. Since then, they hve been considering writing n rticle for this mgzine entitled `How ot to Build Mixer'. I hsten to dd tht they were very hppy with the Trend desk but discovered mny problems which hd to be overcome nd which re never mentioned in the usul build - -mixer rticles. Adrin lbbetson is obviously very busy t Wessex studios. When I spoke to him, he hd no time for detils, only for the nmes of few of the people who hve been in this month. Lovelce Wtkins, Brotherhood of Breth, Phil Pickett, Don Hunter, Vic Flick, onnie ppenheimer, Putney Bridge, icky Beumont, Mike Btt of Belfrey Productions, Sylvi Mceil, Tony Mculey, oger Greenwy, Jimmy Wilson, Milkwood, Les eed, Gerry Monroe, the Andy oss rchestr, nd ew Frontier. Mike Hugg, Mnfred Mnn's ex- drummer, hs been recording complete lbum of his own mteril t Mximum Sound Studios. Kleb Qule, oger Pope nd Elton Den re mong the musicins fetured with Mike. Mnfred hs been in with his new four -piece bnd which includes Austrlin led singer nd guitrist, Mick ogers. Studio mnger Dve Hdfield described the bnd s `funky nd hevy' nd sid tht they were trying to get live -type sound in the studio. Freddie Mck nd Sounds, in the process of recording n lbum, hve lso been ttempting to obtin the feeling of live performnce. Dve explined tht lot of groups now feel tht they should get wy from the `clinicl' studio sound s it is totlly different from wht they sound like on stge. And who could rgue with Freddie Mck, number nine in the top ten world hevyweight chrts few yers go, nd currently n ABA instructor? ther work t the studio this month hs included film music for Mid Atlntic, Brin Short single for Trnstlntic, trcks by Hokus Pokus produced by Kenny Lynch, nd peppermint mtchsticks d. Mximum recently went 16 trck with n 8,000 -plus Scully. The recording rte is 24 per hour, 24 hours dy, seven dys week, which is very resonble for 16 trck fcilities. Dolby 361 hve been instlled, nd vrible speed unit is now switchble to ny mchine. Soon nother two trck Scully complete with Dolbys is to be purchsed. ext door to the studio, t 490 ld Kent od, Dve Hdfield hs just opened rehersl room clled the 490 ehersl Suite. Groups will be ble to prctise here t ny time of dy or night for only 1.25 per hour. The price includes the use of mono recorder with single microphone, the room is plesntly decorted, nd clients hve ccess to vending mchines. Dve Hdfield is lso the studio mnger of Mjestic Studios in Clphm. Hl Crter hs been in to record powerful single by Billy Fury, nd Gerry Shury hs been rrnging film music for Bckfire, film strring Edwrd Woodwrd. A Colonel Bgshot lbum hs been completed nd sent to the Sttes for relese in the ner future, nd Proclim records hve been recording lrge orchestrl versions of songs recently performed in the first Portu- guese Song Festivl. The rtists here were Soul y nd ick Jones, with rrngement nd production by John Hwkins. Mike Morton nd his Congregtion hve been continuing their successful on Slop Top Twenty lbums, nd re now relesing these t the rte of one per month. Belsize Productions re now strting n lbum for the group Jigsw. At Pn Studios, Hmpsted, uby Murry hs been mking single, guitrist Ike Isc hs been in with Gordon Lottinger, nd zreth hve lid down few trcks. Budget lbum mteril ws rrnged by Bill Hutchings nd directed by Grhm Fcher for the Decon lbel. Songwriters Simon Plug nd Grimes hve been in with bss guitr, drums, electric nd coustic guitrs, pino, strings, trumpets, nd tubs, to record for President ecords. Uncle Brin Mtthew recorded number of firy tles, sid by n enchnted studio mnger, Vic Hwley, to be well worth listening to, nd much too good for children. Hns Christin Andersen nd the Brothers Grimm wrote the stories which include such clssics s The Swineherd nd the Princess nd The Tinder Box. Something completely different for Trident engineer Ken Scott ws the mixing of n lbum for the Monty Python crowd. Dvid Hentschel recorded John Kongos single which ws produced by Gus Dudgeon, nd oy Bker recorded Jumbo. The engineers hve lso been recording Genesis, the Tremoloes, Vn der Grf Genertor, Chris Money, ymond Froggtt, Hugh Lloyd nd Bill Pertwee. Gsoline nd Aubrey Smll were mixed. Mlcolm Jckson still finds time to work t the Jckson Studios in ickmnsworth. A footbll tem hve recorded song for Denver records, but no further informtion is vilble t the moment. If the record is nything like the efforts of other footbll tems, I hope we hve herd the lst of it. Mitey M (Miniscule rchestr) hve been lying down bcking trcks using metl AB spools nd trombone mutes (for bnging) in order to get completely unorthodox sounds. The mn behind this is John Dunsterville, who is now mking rock - folk group out of Tmlin nd is recording old English folk songs with fuzz guitr. Doug Flett nd Guy Fletcher hve been in to record demos nd msters for their own compny, Big Secret Music, nd Tony Bck ccompnied by the Hurdlers mde single to be relesed shortly on the Adrhythm lbel. John Bles of Studio epublic does ll mobile sessions for Jckson nd ws recently employed to record wind orchestr in Kent for Boosey nd Hwkes. Mlcolm hs just obtined qulified engineer for studio in Tel Aviv, nd now hs severl engineers left on his books, so nyone looking for nother pir of hnds knows who to contct. Incidentlly, mny people hve been writing to me to see if I cn get them job in studio. I cn't. If I know of ny vcncies I m hppy to pss on the informtion, but there re so mny people looking for studio work t the moment tht posts re filled lmost s soon s they become vcnt. ne studio mnger told me tht he receives t lest six letters every dy from would -be engineers, nd he hs no vcncies. He estimtes tht the mjor studios must receive twice s mny pplictions s he does so for newcomers the prospects do not look very bright t the moment. =H I I I t Jo LlCgl AMD0g0A 21=1L01MgL'S' DISCTHEQUE EQUIPMET STUDI ECDES - MIXES - AMPLIFIES 57 JAMESTW AD LD.W.1 Tel : nullnnlllnnilnnn111n1nnnuln1un11111nllnlullr : lll rllll luiili111un11n1n1111nn111111nnllllnl n11111n1n1nln11ululnnnlllnl1nn11nlnlllllullnunnullunnlulnnllnllnnlnllllnllllltuui. 624

21 b I 1crophone Suruej W Ó f W > I-? F úá á Y C1 má z cc W u Z > H >"- tnz z> ÑE W u á W o 4! Ñ z cc LU? H ú c7.. Y U mm o Z cg W Z D á ft. >. I- j.. F Z z> ILI r W u d CAPACIT MICPHES C12A Stnd Vrible 20 (mx) 50, C24 Stnd Vrible 20 (mx) 50, C451 Stnd Vrible AKG Equipment Ltd, 182/184 Cmpden Hill od, Kensington, London W8. dio Microphone Systems nge of systems to suit UK nd overses frequency stndrds. Supplied with AKG D109 or with own cpcitor hed. Prices from 184 to 275. Audio Ltd., Wendell od, London W mni - Crdioid Vocl Bss roll -off Crdioid Hnd vocl mni Crdioid 20 30, Vocl Bss roll -oft CB1000 Crdioid 20 30, Detchble Cpsule bss CC1000 Cpsule mni CC1050 Cpsule Crdioid CC1051 Cpsule Bss roll -off U87 Studio mni, crdioid Figure of eight - 50, U67 Studio mni - 50, Crdioid Figure of eight Equl KMA eck Crdioid - 50, KM63 Studio mni - 50, SM69 FET Studio mni, crdioid 22 50, stereo Figure of eight eumnn (F.W.. Buch Ltd, Holbrook House, Cockfosters, Brnet, Hertfordshire.) ptterns - DC20 /21 - mni DC DC73 Crdioid DC83 mni DC96 Crdioid TC4V - emote vri- pttern 50, FP92 Pre mni or crdioid polrised to order ST8 Stereo emote vri- pttern Power units from 2250 Perl (Jgor Interelectric Ltd, Mercury House, Hnger Green, Eling, London W5.) crdioid (CE mm extension tube: 1715) LBB9080 H/S Uni (CE mm extension tube: 1860) LBB9078 H/S mni Clrec (Clder ecordings Ltd, egent Street, Hebden Bridge, York- LBB9073 H/S Uni shire.) LBB9060 Stnd vrible - 20á & 0 2- Philips (Pye TVT Ltd, Coldhms Lne, Cmbridge). MKH105 - mni MKH405 Boom Crdioid C092 Electret mni MKH815 - Uni C096 Electret Crdioid Sennheiser (Hyden Lbortories Ltd, 12/13 Polnd Street, London Egle Interntionl, Hether Prk Drive, Wembley HA01SU. W/V 3DE.) 4136 Stnd Crdioid 32 30, ITT Components Group Europe, Stndrd Telephones & Cbles Ltd, Electro- Mechnicl Product Division, West od, Hrlow, Essex. KM88 H/S Vrious 20(mx) 50or SM84 Stnd Crdioid or KM73 Studio mni KM74/75 Studio Crdioid KM76 Studio mni, Crdioid Figure of eight U77 Studio mni,crdioid Figure of eight KM83 Studio mni - 50, KM84/85 Studio Crdloid 25 50, KM86 Studio mni,crdioid Figure of eight - 50, MVIG CIL MICPHES D11 H/S Crdioid ,50 K 0.23,2-0E11 D11S Stnd Crdioid DSt11 Desk Crdioid D12 Stnd Crdiold D14S Stnd Crdioid ,40K 022, D58 Stnd oise- cncelling Stnd mni D190 Stnd Crdioid D200 H/S Crdioid D202 H/S Crdioid (1 khz) D224 H/S Crdioid (continued on pge 627)

22 I. IC G FET C.451 modulr condenser microphone systems for utmost flexibility in ll operting conditions A bsic pre -mplifier employing dvnced FET trnsistor circuitry is vilble for use with rnge of interchngeble cpsules. These re principlly directionl, shrp directionl nd omni- directionl. A long directionl tube enbles the system to be used s gun microphone, whilst specil version is for use on booms in TV nd film studios. Vrious power sources re vilble in the form of bttery unit, multi -chnnel mins power unit nd the C volt power unit for phntom powering. We shll be plesed to send full technicl informtion or demonstrte without obligtion. AKG MICPHES re vilble to cover ll possible requirements from domestic tpe recorders to P.A., brodcsting, recording, TV nd film studio use nd re extensively used in these fields. A.K.G. stereo hedphones re lso of high qulity nd competitively priced. AKG EQUIPMET LTD. Erdley House, Cmpden Hill d., London W8 7AS. Telephone : '3895 Ambiophonie Unit Studio ibbon Microphone lllll1111 Amplifier Three Units of Distinction by [9mpín) These nd mny others mnufctured by the compny with forty yers experience in sound products. GAMPIA EPDUCES LIMITED rmpinj Hnworth Trding Estte, Feithm, Middlesex. Telephone: SUD EQUIPMET JACw; X i (AMAI)

23 d w o f Y > u w f- m u.- z co 13 j"--0 Z - ó^ w m r/) i 1-: E I- r z > ux. C ÿ E w U..J w o w l- tr YF U Eá Y u m 4 Z2 l- á C ú Z _ y0j y r w u D501 H/S Crdioid H/S Anti -oise D707 H/S Crdioid ' D900 H/S ifle D1000 H/S Crdioid AKG Equipment Ltd, 182/184 Cmpden Hill od, Kensington, London W.8. BEMIC 1000 Hnd mni BEMIC 2000 Hnd Crdioid Bng & lufsen UK Ltd, Estbrook od, Gloucester GL4 7DE M88 Stnd Uni 22(120e) M67 Stnd Crdioid or M69 Stnd Crdioid ' M101 Stnd mni X1 Stnd Crdioid M411 Stnd Crdioid M410 Stnd Crdioid M111 eck mni Beyer Dynmic, (GB) Ltd, 1 Clir od, Hywrds Heth, Sussex. 709 H/S Crdioid H/S Uni ' Bouyer (Dougls A Lyons nd Assocites Ltd, 8 yecotes Med, London SE21). C450 H/S Crdioid or 30/ Clrec (Clder ecordings Ltd, egent Street, Hebden Bridge, Yorkshire.) 676 Hnd Crdioid , high - 29 stnd 627 Hnd, Crdioid , high - n pp. stnd 655C Hnd mni 50,150, A Hnd, mni stnd 635A Hnd, mni stnd 623 Stnd mni - 150, high Stnd mni - 150, high Lvlier mni Electrovoice (Gulton Europe Ltd, The Hyde, Bevenden, Brighton.) DP4 /L Hnd mni DP4 /X Hnd mni DP4 /M Hnd mni DP4 /H Hnd mni - 50K DP6/L eck mni DP6/X eck mni DP6 /M eck mni DP6 /H eck mni - 50K Grmpin eproducers Ltd, Hnworth Trding Estte, Felthm, Middlesex. 4037A/C Hnd mni Stnd Crdioid ITT Components Group Europe, Stndrd Telephones & Cbles Ltd, Electro- Mechnicl Product Division, West od, Hrlow, Essex H/S mni 5-30 H/S Uni 5-43 H/S mni 4-20 H/S mni 4-30 H/S Crdioid FMT404 /H dio/ Uni hnd 25,200, ,50 K? s bove 0.2 s bove s bove ? s bove Lustrphone Ltd, St George's Works, egent's Prk od, London W1. DM16HL Stnd mni 500,50K DM18HL H/S mni 600,50 K - - DM18HL H/S mni - 600,50K DM31C H/S Crdioid K DM34C H/S Crdioid K DM58HL Stnd Crdioid ,50 K 0'4 11 UD5HL H/S Crdioid ,50K 0'8 8 Egle Interntionl, Precision Centre, Hether Prk Drive, Wembley HA01SU. 76A Speech Uni 10 or A Stnd mni A Music Uni 10 or A eck mni - 10,200 or k 88 Stnd mni - 10 or C121 Stnd Un' - 10 or C133 H/S Uni k or 80k Melodium (Keith Monks Audio Ltd eding od South, Fleet, Hmpshire.) 643 Stnd /gun Uni 25 50,150, Gun Uni 23 50,150, Gun Uni , high Boom Crdioid 20 50,150, EIS Boom, Uni hnd 627 MB150T Stick/Std mni '2 5 MB160F - mni MB160 - mni MB170S Stick /Std mni MBI70 Stick /Std mni MB170T Stick /Std mni 700,50 K (continued on pge 629)

24 M EET THE FAMILY. We've been in the microphone business for over 40 yers now. And in ll tht time we've built up quite fmily. ibbon mikes, moving coil mikes, hedphones, stnds, ccessories, the lot. ver 50 in fct. All these products, mde to the sme high coustic qulit y tht hs set stndrds ll over the \'. orld. All these products re shown nd explined in detil in the Beyer Dynmic Ctlogue. Which, if you re t ll interested in better equipment, is something you should send for. - BEYE DYAMIC To: Beyer Dynmic (GB) Ltd., ì Clir od, Hywrds I leth, Sus ex. Telephone Hy wrds Heth 510)3 Plese send me lull prticulrs nd illustrted I,rnchur. -f_the Beyer Dynmic products. me lddress 626

25 {y o W I- 7. z V Q Y U. m Z Q Q u. et W Z C ÿ t > F- >^ F Z j yzj ow,...e W W Q S W cl. } F- Z F V Q Y V m9 Z ' Q u.0 V z á. >. i- > Z W y E W MB270S M B270 MB270T MB220 MB220T MB215 Stick /Std Stick /Std Stick/Std Twin stereo Twin stereo Studio Crdioid Crdioid Crdioid Crdioid Crdioid Crdioid ,50 K ,50 K Mikrofonbu (Denhm & Morley Ltd, 173/5 Clevelnd Street, London W1.) 700 H/S Crdioid &40K H/S Crdioid S785 ser. Stnd mni or H 01,1.6 Turner (Millbnk Electronics Group, Bellbrook Estte, Uckfield, Sussex) IBB MICPHES BM5 Stereo Fig8-180 perch. H/S Bng & lufsen UK Ltd, Estbrook od, Gloucester GL4 7DE - 30 D44 H/S Crdioid LD18 H/S mni LD191 H/S mni &Hi D16 Cpsule Crdioid D34/36 H/S Crdioid or & Hi HM47 eck mni HM49 H/S mni FS67LS H/S Crdioid FS67BS H/S Crdioid - Hi F69 H/S Crdioid Perl (Jgor Interelectric Ltd, Mercury House, Hnger Green, Eling, London W5.) EL6015/11 H/S Crdioid EL6016 /11 H/S mni EL6025 H/S Crdioid ,25 K 0.28 & EL6026 Pnel/ Crdioid Stnd EL6033/10 H/S Crdioid /mni EL6035/10 H/S Crdioid EL6036/10 H/S mni EL6037 H/S Crdioid ,25 K 0.28 & EL6042/05 H/S mni EL6061/02 oise Crdioid Cnc. LBB9050/05 H/S Crdioid LBB9500 H/S Crdioid Philips (Pye Business Communictions Ltd, rchrd od, oyston, Herts.) MPD ser. vrious mni - 30/ MMD2 eck CPD ser. H/S semicrd 14 30/50, 0.04 t /600, 30/50 50 K U D1 H/S Uni 14 L, M, orh,0.04 t 22 s bove 30/50 SL1 H/S mni - LorM SL2 H/S oise cnc. 16 L or M eslosound Ltd, Spring Grdens, London od, omford, Essex. MD21 H/S mni &30K M D 211 H/S mni M D 214 eck mni M D420 H/S oise -cnc Sennheiser (Hyden Lbortories Ltd, Est House, Chiltern Avenue, Amershm, Bucks.) 629 M160 Stnd Uni 20(120 ) M260 Stnd Uni 20(120 ) M130 Hnd Fig M320 Stnd Uni M360 Stnd Uni M500 Stnd Uni 20(120 ) or200 (500 ) Beyer Dynmic (GB) Ltd, 1 Clir od. Hywrds Heth, Sussex. M8 Stnd Fig8 - upto57k M8A Stnd Fig8 - upto57k MSS Stnd Fig 8 - up to 57 K Film Industries Ltd, Sttion Avenue, Kew Grdens, Surrey. G1 Stnd Semicrdioid 10 25,200, 00316, or 0.086, 50K 015 or 1.37 G2 Stnd Fig 8 - s bove s - bove Grmpin eproducers Ltd, Hnworth Trding Estte, Felthm, Middx. M6 Stnd Fig 8-50 or Melodium (Keith Monks Audio Ltd, eding od South, Fleet, Hmpshire.) C2ser. Stnd semi -crdioid 10 30/50, /600, 30/50 & 50 K SI ser. Stnd Fig8-30/50, /300 eslosound Ltd, Spring Grdens, London od, omford, Essex. SM33 Stnd Crdioid 16 30/50, 0.04, / Stnd Fig 8-30/ (50) /250 or High 3155 Hnd Fig 8 - s bove 0.01 (50) Hnd Uni 16 50, 0-05 (50) /250 Shure Electronics Ltd, 84 Blckfrirs od, London SEI Stnd Fg 8-30 or Lip oise -cnc or Lip oise -cnc or ITT Components Group Europe, Stndrd Telephones nd Cbles Ltd, Electro- mechnicl Products Division, West od, Hrlow, Essex.

26 I CALEC J. J. Frncis THE PFESSIAL F PFESSIALS A CMPLETE SEVICE FIST CAME MICPHES The 1000 Series Condenser Microphones, of which the ltest ddition is illustrted, re now ccepted stndrds in mjor TV, dio nd Sound Studios everywhere. PE -AMP,' EQ MDULE TYPE PQMI2 CB 1000 PE -AMP with CCI 050 CAPSULE AD W MIXE MDULES, DESKS..,. The CALEC Modulr system llows n infinite vriety of desks to be ssembled to customers specific requirements. A rnge of non -modulr portble mixers is lso vilble. ACA III's UGETLY EQUIED F CASH i AGAS We re the cknowledged off - the - shelf stockists of nd ccessories for immedite delivery Sennheiser, A.K.G. nd Audio dio Mikes... AD MIT SPEAKES Working in conjunction with IMF, CALEC hve produced Monitor to hndle the power without compromise! Plese send detils of ll Clrec Audio Products We crry n extensive rnge of SEHEISE, A.K.G. nd Audio dio microphones nd hve knowledgeble sound sense nd re redy to give unbised dvice on eve ry s pect of sou nd recording nd reproduction. If you wnt to tlk professionl - come to the professionls. To M CALEC -IMF TASMISSI LIE MIT CALDE ECDIGS LTD EGET STEET HEBDE BIDGE, YKSHIE Phone 2159 Distributed in Scotlnd nd S. Englnd by Beyer Dynmic, Clir od, Hywrds Heth, Sussex. Phone The professionl equipment stockist for SE HEISE, A.K.G., BEYE, AUDI -ADI MICPHES, PEFECTS, etc. J. J. FAC 123 ALEXADA D., HSEM, s (WD GEE) LTD D.B. Tel :

27 Around the Studios BY KEITH WICKS TTIG MUSIC CETE H1S studio hs limited fcilities compred 1 with most of the ones I hve visited. evertheless, high qulity recordings re being mde here t the very resonble rte of 5.25 per hour for four trck work. The owner, Bernrd Proctor, is ploughing bck profits in order to purchse more equipment so improvements re being mde ll the time. I tlked with Bernrd Proctor nd his engineer, Steve Vughn, sking first how the studio cme into being. BP The studio ws the originl Tooting Music Centre, selling instruments nd music. A bigger shop becme vilble up the rod so we moved in there with the ide of using these premises s rehersl rooms. Then I thought I might try my hnd t running recording studio so I mentioned the ide to Steve who used to come into the shop nd who I knew ws interested in recording. KW So is it true to sy tht your recording experience hs been obtined minly through using equipment in music shop? BP It's not just cse of being in music shop. I ws in showbusiness for 25 yers so stge -wise, sound -wise nd music -wise, I lerned lot. I plyed the hrmonic nd did film work, bcking trcks, nd lso performed on the stge s vriety rtist. KW Do you ever wind up doing hrmonic bcking on studio sessions? BP t hve done this, but not very much. I'll probbly strt doing more of tht sort of thing but t the moment i hve lot to do with the shop nd not much to do with the studio. KW When did you build the studio? BP We set everything up lst ovember, nd were bit short of equipment when we strted. The first thing we did down there ws Hot Chocolte's You Could Hve Been A Ldy. We did demo of tht one lthough we didn't hve ny limiters then. We just hd two trck Allen nd Heth mixer, nd evox two trck recorders with selsvnc. After we hd been going six months we bought our four trck TD recorder, which hs electronics by ichrdson. The mixer ws lredy built for four trck nd it ws simply cse of plugging in extr modules. Actully, I hdn't intended going four trck for bout yer but we got such good reproductions nd good reports stright wy -nd people were sying tht it wsn't like the usul demo sound - tht I ws more or less forced into spending lot more money in order to expnd it into four trck studio. An importnt dvntge of our studio is the fct tht we hve music shop full of equipment for nyone to use. KW How mny musicins do you think you cn ccommodte? BP With ll the ger in there 1 should sy bout 14 musicins. The point is tht when most people quote how mny their studio holds they tlk in terms of just violins or just trumpets. So we hve to think in those terms nd if we took out ll the ger it could hold bout 25 or even 30. I sy tht becuse I remember the wy we used to fit in the pit bnds when I used to be on stge. You'd ll be seted there in rows. KW Who ws responsible for the coustic design of the studio? BP Tht ws done between Steve nd myself. We didn't hve ny outside consultnts in nd we were surprised how well it turned out. othing specil ws done. I ws told tht the ctul size nd shpe of the plce would give very good recording sound becuse there is not one wll exctly opposite nother. The roof is quite low, but we couldn't do nything bout tht. However, we do get good seprtion nd good sound. The coustic screens we mde ourselves. They hve fibreglss nd hessin one side nd coustic tiles the other side. The wlls re sound proofed with fibreglss, chicken wire being lid over it to hold it up. This is covered over with coloured hessin. KW Control room equipment. Let's strt with the Allen nd Heth desk. Is this stndrd model? BP It's got 10 chnnels, four outputs nd two built in limiters. SV It's stndrd Allen nd Heth desk with one or two extr items dded to my specifiction. For exmple, there is smll speker for monitoring wht goes on to the foldbck system. KW I notice tht you hve got PPMs on the four trck mchine, lthough the meters on the desk re VUs. Steve Vughn t the Allen nd Heth desk 631 SV In fct, I prefer working with PPMs, but when the mixer ws mde Allen nd Heth didn't do PPM metering. I think tht we'll keep the present combintion s it gives me choice of using VUs or PPMs. KW Wht microphones do you use here? SV Mostly AKG. We've got one eumnn, KM56, which cn be switched to crdioid, figure of eight, or ll round. We've lso got two Beyers M160s nd n Americn mike, Metro - sound tht somebody brought into the shop. I tried it out in the studio nd it worked quite well so I kept it down there. All the rest re AKGs. A 202, 224E, four 3451s, which re very good ll round mikes, nd D30. i don't know how common these re. I got one becuse I used to use one t lytnpic for bss drum. Tht's wht 1 use it for here. It's like n elongted version of the D20. KW You've got pir of Lockwood units for monitoring. Tnnoys inside presumbly? SV Tnnoy Golds. BP By the wy, we'll shortly be getting echo pltes. They re cheper thn EMTs nd I've forgotten who mkes them but they re very good. We're going to hve n echo return module built for us by Allen nd Heth. The pltes mesure bout 2 m by 1 tn. They don't hve so much djustment on them s EMTs but they re good. We re lso going to get some more limiters, more verstile thn the ones built into the desk. It costs lot to buy new equipment but the studio wrrnts it. If we were just flinging stuff out tht nobody bothered bout, we wouldn't be willing to spend so much. KW Wht re you turning out these dys? BP We're putting out Drgonmilk record on the Becon Lbel. This will be relesed very soon now. We re lso doing number of msters nd pressings for vrious people nd they re hving them issued on the shop lbel which is clled Pm. KW Wht is the Mp lbel I sw in the shop? BP Tht is lbel of mine which we use to sve people hving to hve blocks mde up. KW Wht hs been issued on Mp? BP ne LP, single, nd we re now in the process of hving nother LP nd two singles pressed. The LP we've hd issued is religious one tht is being sold throughout the churches. Its clled Youth For Christ nd fetures Ptrick Booth with instrumentl bcking. We recorded the Western Echoes t the shville ooms in Kensington. They hve lredy hd single out nd re now hving single with their LP. KW n the subject of discs you hve cutting room bove the music shop. BP Yes. We've got n MSS three speed cutter with Grmpin hed. We hd heted stylus put in by Grmpin to lower the cutting resistnce, nd mke the cut less noisy. KW Any future plns for reduction room, or other expnsion? BP ot t the moment but we might use the room bove the studio for video work -tht sort of thing. Also, if we strt issuing lot of records we could even do the photogrphy for the sleeves.

28 ri`he recent introduction of high -qulity electronic udio dely lines using integrted circuitry is n exciting new development in the genertion of synthetic reverbertion. However, dely lines re essentilly monophonic devices, wheres much of the modern demnd for synthetic reverbertion requires two chnnel, or even four chnnel, spred of reverbertion. ne of the most promising uses of synthetic reverbertion is not merely to dd richness to sounds, but lso to simulte the chnges in reverbertion qulity tht occur nturlly s the position of live sound is ltered. The chllenge tht fces new genertion reverbertion devices is thus two -fold: to provide spred of reverbertion rther thn few discrete sources; nd to provide chnges in the qulity of reverbertion to simulte the effect of sound sources occupying quite distinct positions. For the foreseeble future the cost of electronic dely lines is likely to remin quite high, nd so we re fced with the problem of generting convincing reverbertion using s few of them s possible. The following ccount suggests possible new configurtions of dely units to chieve the bove ims economiclly; sketch is given of the principles of the suggested mode of use, which is clled the `orthogonl mtrix feedbck' technique. Bsiclly, `reverbertion' is merely the effect obtined by dding to sound succession of delyed versions of tht sound. everbertion is distinguished from `echo' or `flutter -echo' by the lrge number of, nd the short durtion between, the successive delyed sounds. To qulify s reverbertion the time intervls between successive delyed sounds should be less thn 30 ms, nd these intervls should grow shorter nd more rndom s the reverbertion dies wy. For stereophonic use it is dditionlly importnt tht the vrious delyed sounds re directionlly homogeneous, i.e. come from more or less rndom directions; this is more importnt for lter delys thn the erlier ones since in rel life erly reflections often rrive from wlls close to the originl sound. Up to now there hve been three methods of providing stereophonic reverbertion, ll with disdvntges. The first is to use stereo pir of microphones in reverbertion chmber in which the sound is reproduced over one or more loudspekers. While cpble of excellent qulity, this method offers little control over the reverb qulity nd is rther imprcticl in its demnds on spce nd its susceptibility to coustic interference. A second method hs been to pn -pot severl monophonic reverb signls into the stereo imge. This does not give convincing stereo spred. The third, most widely ccepted method, is to use soclled stereo reverb plte, which in fct is reverb plte with monophonic input nd with two spced pick -ups on the plte to provide n output with stereo spred. ne disdvntge here is tht precisely the sme pttern of reverbertion is imposed on ll sound inputs, rther thn pttern continuously vrying with the reproduced position of the sound. Another difficulty with stereo reverb pltes is tht the stereo spred of the reverb is non -idel if spced pick -ups re used. Coincident directionl pick -ups on the two -dimensionl plte cn, however, give more uniform stereo spred of reverbertion. Clerly we cnnot produce convincing stereo spred from single monophonic reverbertion device, whtever its operting principle. At first sight it would seem tht two such devices would be hrdly more dequte for producing continuous spred -but then how often hve first ppernces proved deceptive? Let us suppose tht two mono reverb devices re vilble, nd tht these hve differing dely times. For the purposes of the following discussion it is convenient to regrd them s simple dely lines, lthough in principle more complex devices such s reverbertion springs could lso be used in the mnner suggested. The simplest wy of turning dely line into reverbertion device is to pply feedbck. If the output of the line is fed bck nd mixed with the input, then the signl will go through the line time nd time gin (fig 1). If the dely in the line is T milliseconds then signls will emerge t times T, 2T, 3T, etc. Such rever- bertion sounds exceedingly monotonous. Another considertion is tht if the signl cquires gin of x db fter one pssge through the dely line nd feedbck pth, then it will cquire gin of x db fter pssges (-FIG I BASIC FEEDBACK EVEE UIT A00 FIG. 2 FEEDBACK EVEB UIT USIG T ADD CI 632

29 PAT E BY MICHAEL GEZ 7 DELAY LIE )ISSIMILA DELAY LIES LIME 1.IE 2 4iDL J J through the feedbck loop. The gin of the feedbck loop thus hs to be less thn one to void build -up nd howl -round nd this hs to hold t ll frequencies. In order tht the dely T be short enough (30 ms) to be cceptble for reverbertion nd tht the reverbertion time be of the order of two seconds it is necessry for the sound to ttenute bout 60 db fter 60 psses through the feedbck loop. Thus to prevent n excessive vrition of reverbertion time, the gin of the whole feedbck loop must lie within the rnge db to -14 db t ll frequencies. If t ny frequency the gin of the dely line is mere 1 db too high howl -round will result. Thus dely lines used in feedbck mode to provide reverbertion hve to meet stringent frequency response requirements which tpe dely meets only fter creful trimming of the frequency response, nd even then the problem of consistency rises. Most so- clled reverbertion units bsed on tpe involve time delys much longer thn the required 30 ms nd produce flutter -echo. Mgnetic drum or disc delys re potentilly better, s consistency is ensured by the lck of physicl contct of the mgnetic heds with the drum or disc. However, purely electronic delys should prove superior to either, lthough their technologicl glmour should not disguise the usefulness of mgnetic drums or discs. However, the unplesnt reverbertion qulity obtined by simple feedbck is not relly of much interest here nd hs been discussed minly to mke the principles of more complex feedbck systems cler. For monophonic use the monotony of the reverbertion cn be gretly reduced by using two dely units of dely T1 ms nd T2 ms respectively corrected in prllel s in fig 2. By plcing feedbck loop round the prlleled lines sounds my pss successively through either of the lines in ny order, giving rise to delys of the form T1, T2, 2T1, T1 +T2, 2T2, 3T1, 2T1 -f -T2, T2-} 2T1, etc. Furthermore, s there re two wys sound cn hve dely Ti +T2, either pssing first through the Ti dely line or first through the T2 dely line, it will be seen tht the mplitude of the signl with dely TI -I-T2 will be twice s high s tht of the 2T1 or 2T2 delyed signls. Similrly, the 2T1-1-T2 delyed signl cn pss through the system in 3 ( = 3C2) wys, nd so hs n mplitude gin of three times tht of signls tht hve pssed through just one line three times. Similrly, the (sy) 4T1 +3T2 signl cn hve pssed through the system in 35 (---7C4) different wys, nd hs n mplitude gin 35 times tht of signls tht hve pssed through just one line seven times. Thus it will be seen tht the feedbck system of fig 2 rpidly emphsises the 'cross- delyed' signls tht hve pssed through both lines, s compred to the 'repet- delyed' signls tht hve just kept going round nd round one of the lines. However, the cross -delys will only hve the desirble property of being resonbly rndom if the two bsic delys Ti nd T_ re incommensurble, i.e. if the rtio T, /T2 cnnot be expressed s simple frction. If T, /T, were frction of the form n /m, then the cross - dely mt1 +nt2 would be the sme s the repet -delys 2mT1 nd 2nT2, which would cuse much of the undesirble repet -delys to be reinforced by the cross -delys. Idelly, the rtio T, /T2 should be s fr from ll frctions with smll numertor or denomintor s possible, nd should be between # nd 1 but not too close to either. In these respects, the Grmpin monophonic spring dely is ner idel, with its two spring delys of 29 nd 37 ms hving rtio 0.784, lthough the Grmpin's mechnicl feedbck system is not quite the one described here. It is importnt to note tht the signls tht hve pssed through the system of fig 2 in mny different wys to form dely mt, +(n -m)t2 will only dd up in mplitude if they re in phse with one nother, nd they cn only be in phse if the dely of the two lines does not vry over periods of few seconds. This mens tht the feedbck reverb system of fig 2 will only work s it should with tpe delys if the wow nd flutter is low. Becuse of the sttisticl nture of speed fluctutions, signls tht hve mde 60 trversls of the feedbck loop in two seconds with n rms wow nd flutter of 0.1 per cent will hve two -thirds probbility of emerging within 0.25 ms of their nominl dely. This indictes tht wow nd (continued over) 633

30 I SYTHETIC STEE EVEBEATI continued flutter (unweighted!) hs to be kept down to the highest studio stndrds for frequencies bove I khz to emerge unttenuted from fig 2 -type reverb unit using tpe delys. In generl, one gets the impression tht tpe is being pushed to the limits of its performnce when used to provide reverb, nd relibility is better chieved by working well within the tolernces of n electronic dely. In order to prevent howl -round, the gin of the feedbck loop in fig 2 hs to be kept well below unity becuse of the mplitude build -up of the cross -dely signls. Were the outputs of the two dely lines more or less independent the output energy would be twice the input energy, s the energy in ech of the two lines would be dded. If this were the cse, then gin of just less thn -3 db would prevent howl- round. However, n nlysis of the coefficients ncm of the mtl +(n -m)t2 delyed signls show tht gin of less thn hlf (-6 db) is necessry to prevent howl- round; the energy in such feedbck system with gin just over hlf cn only build up if the signls in the two lines re virtully identicl, nd detiled nlysis indeed shows tht the sounds in the two lines become virtully identicl fter mny psses. This shows tht one cnnot get reverb with good stereo spred by tking the two outputs of the lines in fig 2, s, surprisingly, the reverb from the two lines colesces into the middle s it decys. Another curious feture of the system of fig 2 is tht the reverb dies wy fster thn exponentilly by smll extr fctor proportionl to the inverse of the squre root of time elpsed. The ground hs now been prepred for describing stereophonic reverbertion unit using just two dely lines. The bsic circuit of two line stereophonic reverbertion unit is shown in fig 3. In such unit, two chnnel stereo signl, which is to be reverberted, is fed into the two dely lines, one chnnel into ech. The signls L nd emerging from the two dely lines re then fed into mtrix circuit FIG 3 IPUTS 2 BASIC STEEPHIC EVEBEATI UIT USIG TW DISSIMILA DELAY LIES A0D GAGED! GAI CTL DELAY LIE 1 DELAY LIE 2 GAI CTL V MATIX FIG. 4 - CHAEL THGAL MATIX FEEDBACK EVEBEATI UIT IPUTS - 4'0 GAGED GAI CTLS; ADD DELAY LIE 1 AD --1 DELAY LIE 2 Ho- DELAY LIE THGAL MATIX t UTPUTS 1 J FIG. 5 WEAKLY- CUPLED PAI F STEEPHIC EVEBEATI UITS P GAI s DELAY LIE 1-1 THGAL MATIX 8 THGAL MATIX SMALL ADC DELAY LIE 2 PUTS GAI / /4 UTS. GAI AD DELAY LIE 3 AD DELAY LIE l THGAL MATIX 8`?L5' THGAL MATIX SMALL 8 634

31 producing two outputs of the form: 11L +12 nd L1= 1= 21L +22 ( 1 ) These mtrixed signls 1.1 nd ' provide stereophonic output, nd re lso fed bck nd mixed in with the respective chnnels of the input to the two dely lines, s in fig 3. Bsiclly this feedbck system provides prepondernce of cross- delys in similr mnner to the monophonic feedbck unit of fig 2. The difference is tht lrge degree of independence is retined between the two chnnels, s long s the four coefficients of the mtrix (formul (1)) re chosen suitbly. The monophonic unit of fig 2 my be considered s specil cse of the bove stereo unit in which the four coefficients in formul (1) re ll unity. This indictes tht to obtin genuine stereophonic reverb the mtrix coefficients hve to be chosen crefully. The simplest wy of ensuring tht the reverbertion energy dies wy ccording to the proper exponentil lw without ny nomlous behviour is to require tht the totl energy of the two outputs from the mtrix be precisely the sme s the totl combined energy of the two input signls. By this mens, s long s the totl energy gin of the two chnnel feedbck loop is set t less thn unity the reverbertion will die wy in uniform mnner, s on the n +1'th pss through the lines the stereo energy will be less thn on the n lth pss by fctor equl to the loop gin. This cn only be the cse for ll possible input signls if pssge through the mtrix leves the totl energy unltered. A mtrix circuit with inputs nd outputs is sid to be orthogonl if, whtever the input signls hppen to be, the combined energy of the output signls lwys equls the combined energy of the input signls. This is equivlent to sying tht the coefficients of the mtrixing form n orthogonl mtrix in the usul mthemticl sense. In the circuit of fig 3, we hve required tht the mtrix used to derive the feedbck signl be orthogonl, nd this mens tht formul (1) describing the mtrixing becomes: L1 =L cos 0- sine } nd, =L sin -F (1) cos() for some vlue of the prmeter. If the vlue of is 0, then the signl fed bck to the input of ech line is the output of just tht line, nd one merely hs two crude monophonic reverb units s in fig 1; these will not give good stereo spred. If the vlue of is smll, sy +1 or ±2, then there is in ddition smll mount of energy bleeding from one line to the other. This sitution is described by sying tht the two lines re wekly cross -coupled, nd this sitution is nlogous to two reverbernt rooms connected by doorwy; ech room hs its own reverbernt qulity, which is modified by the lekge of reverbertion through the doorwy from the other room. The sitution of most prcticl interest is when there is strong cross -coupling between the two lines, corresponding to 0 tking vlues between, sy, +10 nd +80. In this cse, the signl with cross -dely mt,+(n -m)t2 cn hve pssed through the two dely lines in lrge number of different possible wys, nd will hve cquired different gin on ech journey through hving pssed through the mtrix of formul (2) n times. The component of this cross -delyed signl emerging from one dely line will in generl hve quite different mplitude gin to tht component emerging from the other line, due to the differing experiences of the signl with dely mt,+ (n-m)t, depending on which of the two lines it pssed through on its i'th pssge round the feedbck loop. The reproduced stereo position of the signl with cross -dely mt, +(n -m)t2 depends on the reltive mplitudes of the components emerging from the two dely lines. While this process is not esy to visulise, the result is tht different cross -delyed signls re reproduced from wide vriety of different stereo positions, giving stereo spred of reverbertion. Unfortuntely, the mthemticl nlysis of such reverb units is much tougher thn the simple system of fig 2, nd hs not been stisfctorily resolved. However, certin properties of the bstrct formlism (the bsence of frequency independent eigenvectors of the complex mtrix describing the feedbck loop) suggest tht, fter enough psses through the system, the reverbertion energy ought to become evenly spred cross the whole stereo imge, with n equl mount of reverb energy being concentrted in every direction in the stereo groove if the reverb is imgined to be recorded on stereo record. This mens tht there is s much reverb in phse s out of phse, nd the reverb should be idel for mtrix - system surround sound reproduction vi the Snsui or Hfler systems. Such reverb distribution is the sme s given by 90 - ngled coincident crossed figure -of-eight microphones. However, if the degree of cross- coupling (i.e. 0) is substntilly less thn, sy, 20 the reverbertion energy will t first cluster ner the two chnnels, nd tke n pprecible frction of second to spred cross the whole stereo imge. This behviour nicely simultes the live sitution where erly delyed sounds come from ner the direct sound. n the other hnd, vlues of 0 round 45 will more quickly suppress repet- delys, nd give uniform reverb spred fr more quickly. Much experiment is clerly needed to find the optimum orthogonl feedbck mtrices for vrious effects. The orthogonl mtrix feedbck reverb unit cn be modified in number of minor wys: the reverb cn be tken direct from the two dely line outputs before the mtrix nd one/ both feedbck pths cn include phse inversion of the fed bck signls. As before, it is importnt to ensure tht the gins of the feedbck pths nd dely lines re precisely right t ll operting frequencies. For the sme resons, the coefficients of the feedbck mtrix should be djusted ccurtely, using components of t lest one per cent ccurcy. Wheres the effect of wow nd flutter in monophonic reverb unit is to ttenute the treble of delyed echos, in the cse of n orthogonl feedbck unit its effect k to smer the position of the treble of echos, without ny ttenution. ne problem is tht good electronic delys do not yet seem to be vilble in incommen- surble pirs of vlues. For instnce, the Gothm lines re only vilble in precise multiples of 5 ms. It is very importnt for the delys to be incommensurble for the stereo 635 spred to be obtined. Hopefully, mnufcturers will soon remedy this deficiency, s will be discussed further in prt two of this rticle. If more thn two dely lines re vilble, then there is gret scope for experiment with specil effects. If dely lines of dely T,... T re vilble which re mutully incommensurble (i.e. no rtio Ti /Ti hs smll numertor or denomintor), then n -line orthogonl mtrix feedbck reverb unit will be s in fig 4. There is gret richness in the vriety of possible orthogonl mtrixing tht cn be used, the number of prmeters cpble of being vried being -1-(-1). If none of the coefficients of the mtrix is smll, then there is strong cross -coupling between ll the dely lines, nd I would expect the reverbertion energy rpidly to become uniformly distributed mong the chnnels. (The precise definition of `uniformly distributed' would tke us into the higher mths of elliptic geometry but the intuitive mening is cler enough.) Thus three or four mutully incommensurble dely lines should be enough to provide high -grde four chnnel reverbertion lthough detiled nlysis shows tht, idelly, qudrphonic reverbertion should not be distributed completely uniformly. It seems likely tht orthogonl mtrix feedbck techniques will come into their own once units combining strong coupling between some lines nd wek coupling between others re used. As simple exmple of the possibilities. consider the reverb unit of fig 5, using four mutully incommensurble dely lines. To first pproximtion lines one nd two re coupled strongly s two chnnel reverb unit, nd lines three nd four re similrly coupled together. In ddition there is wek cross - coupling between the two chnnel unit contining lines one nd two, nd the two chnnel unit contining lines three nd four. By our erlier nlogy we hve two coustics with certin degree of lekge from one to the other. If the degree of cross -coupling is not too wek then the two coustics will become completely intermixed fter frction of second, but not initilly. It thus seems likely tht we cn simulte the effect of different sounds lying in different prts of building by feeding them into inputs one nd two only for one prt of the imgined building, into inputs three nd four for nother prt of the imgined building, nd into both sets of inputs for intermedite positions. A two chnnel output cn represent microphones in the first prt of the building by using outputs one nd two, cn represent microphones in the second prt of the building by using outputs three nd four, nd other positions by mtrixing these outputs together in different wys. More complex modes of cross -coupling cn be envisged for more ccurte simultion of rel coustics nd much experiment will be needed to test the subjective effect of ll these theoreticl proposls. Menwhile, it is possible tht orthogonl mtrix feedbck will prove to be n economicl mens of using electronic udio dely lines to provide synthetic stereo reverbertion. ext month, methods will be described for ensuring;tht the reverbertion hs n uncolou red qulity, nd suggestions will be given for the design of n economicl electronic stereo reverb unit.

32 EUMA= mtoomm.s miiims The Ultimte in rdio microphones by udio limited Developed out of our originl Audio Ltd. dio Microphone System, we now offer for prompt delivery n improved MS 7 system in which the newest electret cpcitor microphone is used. By slightly enlrging the receiver, we hve incorported block eril filter to gretly reduce cross modultion interference nd fcilitte multi -chnnel opertion. The receiver hs bttery, signl level nd tuning meters, lso plug -in whip eril nd output plug nd led. The trnsmitter is esily conceled in the pocket or bout the user, nd the microphone supplied is smller thn the plug used to connect it. We shll be plesed to forwrd full technicl informtion on request. CMPLETE SYSTEMS FM 184 THES FM 115 MS7H Hnd held model In MS7H, microphone nd trnsmitter re combined in single unit. The trnsmitter is contined within the tubulr hndle which is s esy to hold nd use s ny conventionl hnd held instrument. The microphone cn be crdioid or omnidirectionl. nd is the new electret cpcitor type which offers the dvntge of condenser microphone without the problems of power supply for it. n -off switch is incorported. F.W..BAUCH LIMITED 49 Theobld Street, Borehm Wood, Herts. Tel: Telex: *UHF AD HIGH PWE VESIS F USE VESEAS Audio Ltd. dio Microphone Systems s supplied to users in the U.K. conform preciselyto Post ffice regultions. More powerful systems nd U.H.F. systems cn be supplied for use overses in complince with loclly stipulted operting conditions. Trnsmitters operting up to 500 MHz nd with outputs up to 500mW t 175 MHz cn be supplied. AUDI LIMITED 26 WEDELL AD LD W12 Telephone

33 b I 1cruphones By John Fisher THE generl requirement for most microphones used in recording or brodcsting is fidelity in trnsltion of coustic energy to electricl energy. This implies constnt output over the required frequency rnge, polr response tht is independent of frequency, the bsence of distortion t the highest coustic levels encountered, good response to trnsients, n output level high in reltion to induced, self -generted nd therml noise, insensitivity to externl electrosttic or mgnetic fields nd to wind (drughts); in ddition the microphone should be sufficiently robust to withstnd hndling nd mishndling in use. In prctice no microphone is perfect in ll these respects, or indeed in ny, but some do come much closer to perfection thn others. Certin microphones deprt from these requirements delibertely: for instnce, microphones to be used on lvlier cords bout speker's neck my hve n output rising with frequency in order to offer some compenstion for being screened from the speker by clothes, etc, nd for being off the speker's 'xis'. Similrly, noise -cncelling microphones my be designed so tht their flling bss response is compensted by being used close -to. Directionl properties In ddition to the generl requirements bove, microphones in professionl use my be required to be omnidirectionl (equl in sensitivity to sounds from ll directions), or directionl in order to discriminte ginst indirect sound or sound coming from unwnted sources, or -s in coincident mike stereophony -the directionl properties my be used to produce directionl informtion in the subsequent signl. The two bsic types of microphone my be regrded s the pressure operted (constnt mplitude or omnidirectionl) microphone nd the pressure grdient (constnt velocity or figure -of- eight) microphone. ther directionl ptterns (crdioid, cottge lof, hypercrdioid) my be regrded s being derived from ddition or subtrction of these two bsic ptterns (phse -shift opertion). Pressure opertion A microphone which is designed to isolte the previling tmospheric pressure nd use the vritions in pressure representing sound wves to ctute the trnsducer is clled pressure operted or pressure microphone. Essentilly, it consists of thin membrne (diphrgm) stretched in front of cse contining ir t the previling tmospheric pressure (fig. 1). The instntneous differences in pressure between the ir in front of nd behind the diphrgm cuse the diphrgm to move, nd this movement is trnslted into electricl energy. The force obtined is proportionl to the coustic pressure nd independent of frequency or the direction from which the sound rrives (provided the microphone is smll enough not to ct s n obstcle to sound wves: in prctice some obstruction is inevitble nd this mkes the microphone insensitive to sounds from behind t high frequencies). Since the microphone is sensitive to sounds from ll directions it is termed `omnidirectionl' nd the polr response pttern is nominlly sphere. Pressure grdient opertion In pressure grdient opertion, both surfces of the diphrgm (or ribbon) re open to the tmosphere nd subject to coustic pressures. Since sound reching the rer fce hs to cover slightly greter distnce thn tht reching the front (this difference in pth length my be extended not only by the thickness nd size of the diphrgm [or ribbon] but by the pole pieces nd csing) the pressures t the front nd bck differ in phse reltionship by n mount depending on this difference in pth length. The pressure grdient between the two surfces cuses the diphrgm to move towrds the low pressure side (fig. 2). The grdient (nd therefore output) is proportionl to the extr pth length nd lso frequency, since the smll extr distnce forms n incresing proportion of the wve -length with incresing frequency. When the difference reches hlf -wve- length the pressure reches mximum nd therefter decreses until it reches null where the difference in pth length equls wve -length, nd so on. The mgnitude of this extr pth length determines the sensitivity nd upper usble frequency limit of the microphone. When sound rrives from off the min xis of the microphone, the pressure grdient my be seen to be reduced s the difference in pth length is reduced, until with sounds rriving t 90 to the xis there is no difference in pth length to the two sides of the microphone t ny frequency, nd there is null in output. Plotting the output for sound sources t vrious ngles to the microphone gives polr digrm tht is figure -of -eight rotted bout the min xis, with the rer lobe in ntiphse to the front lobe, i.e. higher pressure rriving t the bck of the microphone is equivlent to rrefction rriving t the front. If microphone opertes close to smll sound source, the wvefront is sphericl nd the pressure grdient is gretly incresed t low frequencies, resulting in output being boosted t low frequencies. This is responsible for the fmilir rise in bss from directionl microphone used close to singer or speker, reching its ultimte (?) in the crooner's microphone. Pressure nd pressure -grdient opertion So fr we hve considered the principles of omnidirectionl nd bidirectionl (figure-of- eight) microphones. A crdioid my be considered s the summtion of n omni nd figure -of-eight of equl on -xis sensitivity. The result is ddition of the outputs in the front, the omni contribution only t 90 nd cncelltion t the rer, giving polr digrm which is crdioid rotted bout the min xis (fig. 3). Alterntively, these microphones my be regrded s phse -shift microphones in which the sounds reching the rer of the diphrgm re delyed by n coustic pth (fig. 4): this is rrnged so tht the length of the coustic pth from the bck of the microphone to the diphrgm through the microphone is equl to the shortest pth round the microphone to the front, so tht there is no pressure difference on the two sides for sounds coming from the rer; but there is reinforcement of the difference in pressure between tht due to the sound rriving t the front of the diphrgm nd tmospheric, due to the shift in phse of sound pssing from the front round the microphone to the bck of the diphrgm. The effective pth length through the microphone is modified by the size of the cvity behind the diphrgm nd the size of the pertures llowing sound to enter from the rer. If the proportion of pressure -grdient to (continued over) FIG 3 ee 637

34 MICPHES continued pressure opertion is incresed, lobe ppers t the rer with reduction in output t the sides nd with nulls between 90 nd I80 to the front fce, to give fmily of intermedite ptterns. FIG. 4 FIG. 5 G TW ULTA DIECTIAL MICPHES Further study bviously it is beyond the scope of n rticle such s this to go into the detiled theory nd mthemtics of microphones. Anyone wishing to pursue the mtter is strongly recommended the BBC Engineering Trining Mnul 'Microphones' by A. E. obertson, published by Iliffe Books Ltd. There re lso interesting BBC Engineering Monogrphs on the design of brodcst qulity ribbon microphone, nd on preferred stereo blnces. Susceptibility to mechnicl shock Crdioid nd bidirectionl microphones re susceptible to mechnicl shock or rumble, s the diphrgm, being light nd controlled by the ir, tends to sty still while the cse moves. In twin diphrgm microphones there is susceptibility to shock becuse unless the diphrgms re connected in prllel so tht the induced rumble voltges which will be in ntiphse, cncel out, there is residul rumble component in ny directionl mode. A single diphrgm omni mike tends to hve the diphrgm controlled by the stiffness of the ir trpped between it nd the bckplte: the result is tht the diphrgm nd housing move together, nd becuse there is no reltive movement, rumble nd hndling noise re t much lower level. It is therefore generlly the cse tht omnidirectionl microphones will be less prone to rumble, mechnicl shock nd hndling noise thn directionl ones. Highly directionl microphones There re purposes for which none of the polr ptterns considered so fr give sufficient discrimintion ginst unwnted sounds off the min xis of the microphone. Where the norml first - order pressure grdient or pressure /pressure-grdient pttern is insufficiently discriminting, second or higher -order pressure -grdient component would give nrrower lobes nd better discrimintion. Unfortuntely there re prcticl difficulties in producing even secohd order microphone tht hs response flt throughout the udio bndwidth. Microphones hve, however, been produced giving cceptble qulity over nrrow rnge of frequencies for speech or sound effects. This cn be done in number of wys, for instnce by using stggered pressure grdient trnsducers or single trnsducer with stggered pertures for the sound to enter, or bundle of tubes or single slotted tube on the front of the microphone (fig 5) -the ide being tht sound rriving from ny direction but stright hed rrives in rndom phsed components through the different pertures or, in the cse of the multi- trnsducer ssembly, genertes out of phse signls tht cncel. Another highly directionl system uses prbolic reflector, focusing sound on to the fce of pressure microphone. These microphone systems find ppliction in film nd television work nd in outside brodcsts of sports events, where restricted bndwidth is cceptble, rther thn in music reproduction. The trnsducers ther thn go stright into the vrious wys of mking microphone with prticulr polr pttern, it is worth looking for moment t the vrious wys of producing signl from sound. There is not room to consider them in depth, nd gin reference my be mde to the BBC mnul 'Microphones' nd to the literture tht occsionlly ppers from mnufcturers. ibbon The ribbon microphone is bsiclly one of the simplest trnsducers, lthough it needs mny refinements to produce something of the qulity of the BBC /STC 4038, which is still one of the finest microphones in professionl use lthough it hs been round for number of yers. The essentils re ribbon suspended between two polepieces, between which strong mgnetic field exists. Becuse the ribbon is open to the tmosphere on both sides there is pressure -grdient opertion nd figure -ofeight polr digrm. In order to preserve the figure -of-eight in the horizontl plne, the mgnet system must, s in the cse of the 4038, be t one end of the polepieces (fig 6); this will modify the polr digrm in the verticl plne, but this is generlly less serious. Where size nd efficiency re more importnt, such s where the mike hs to pper on screen, the mgnet or mgnets my be cupped behind the ribbon nd polepieces (fig 7), s in the eslo B nd V designs; this mkes the rer lobe of the 'eight' both frequency conscious nd modified in size, s smll pressure component is introduced. There my be resonnce cused by the cvity behind the ribbon; this cn be rrnged to mintin the front -fce response where it would otherwise be flling off. Such modifictions to the polr digrm nd the polr response my dversely ffect the stereo imge obtinble with pir of such microphones. In some cses prt of the rer of the ribbon is delibertely enclosed to introduce n equl pressure component, in order to generte pressure /pressure- grdient response (crdioid). This is not lwys successful over wide frequency rnge. The ribbon is normlly corrugted. 638 The purpose of this is to increse the rigidity of the very frgile ribbon cross its width, to increse the complince nd to enble some control over the tensioning in order to plce the low frequency resonnce low enough not to be troublesome, i.e. where it is dmped by the primry inductnce of the mtching trnsformer. A mtching trnsformer is necessry becuse the output of the ribbon is very smll; specilly wound trnsformer is therefore built into the cse of the microphone in order to step up this voltge nd mtch the ribbon impednce (which my be frction of n ohm) to the mplifier input impednce, which my be tens, hundreds or even thousnds of ohms. The cse of the ribbon microphone tends to be lrger thn mny others becuse of the size of the mgnet system, nd specil cre hs to be tken in the design not to ffect the frequency nd polr response dversely; in some microphones (gin the STC 4038 is n exmple) the shpe of the cse my be tilored to improve the response of the microphone t high frequencies. The cpcitor microphones The cpcitor microphone hs for mny yers enjoyed gret populrity in professionl fields, prtly becuse of the good signl -tonoise rtios obtined from microphone of modest dimensions nd prtly becuse, s lterntives to the ribbon's figure -of- eight, the best omni nd crdioid microphones were cpcitors. Essentilly the cpcitor microphone consists of bck -plte full of dmping holes, nd thin metl or metllised diphrgm stretched in front of nd spced slightly from it (fig 8). A high voltge is pplied between the diphrgm nd bckplte through high vlue resistor tht mintins constnt chrge on the diphrgm. Smll movements of the diphrgm cuse smll chnges in the cpcitnce between diphrgm nd bckplte, which re thus reflected s smll chnges in voltge on the diphrgm. These smll voltges re mplified in 'hed mplifier' (fig 9), normlly vlve in dys gone by but now more usully combintion of field -effect nd bipolr trnsistors, which provides high input impednce (necessry becuse of the smll vlue of the trnsducer's source cpcitnce) nd low output impednce (to prevent high- frequency ttenution in the microphone cble). The diphrgm is normlly thin metl or metl -flshed plstic, nd is under tension to rise the diphrgm resonnce (it behves like

35 FIG 10 miniture drum) bove the udio bnd (idelly, in prctice towrds the top of it). Plstic diphrgms hve certin dvntges in construction nd lightness but my be ffected by television lights, for exmple. AKG re now using n embossed metl diphrgm which would pper to hve mny of the dvntges of both kinds while hving climed resistnce to geing nd temperture effects. Hving sid n essentil of the cpcitor microphone is polrising voltge, let me retrct tht: minority use the trnsducer cpcitnce in n F bridge or similr system, which voids the problems of high -voltge lekge nd its ssocited noise nd rcing, nd cn theoreticlly offer much better signl -to-noise rtio. Some of these F types hve been shown to be very successful, but I understnd tht others re troubled by drift, especilly in the presence of high studio tempertures nd powerful lights, cusing deteriortion in the noise performnce. In the form described, the microphone is pressure- operted since the diphrgm is open to the tmosphere only t the front fce. If the bckplte is drilled so tht in ddition to the dmping holes there re holes through the plte, nd these hve free ccess to the tmosphere nd to sound rriving from behind the cpsule, pressure -grdient component is introduced nd there is pressure /pressure grdient opertion (fig 10), the result being crdioid or hypercrdioid depending on the number of holes. Alterntively, the bckplte my be mde of porous mteril which lso llows sound to pss to the bck fce of the diphrgm. A further vrition, perhps best known in the AKG C12 nd C24 vrible polr digrm microphones, is the twin -diphrgm cpsule. In this, two diphrgms re spced smll distnce from ech other by the centrl plte which contins dmping holes nd number of holes connecting the cvities behind the two diphrgms (fig 11). The diphrgms re seprtely polrised reltive to the centrl plte (fig 12), nd the outputs re combined vi isolting cpcitors. Ech hlf of the microphone will hve crdioid response. If both diphrgms re polrised (sy) positive with respect to the centrl plte, the outputs will dd nd the result will be the sum of the two crdioids, which my be shown to be sphere or n omnidirectionl response. If only one diphrgm is polrised, the microphone hs crdioid pick -up; if one diphrgm is polrised positive nd the other negtive with respect to the plte, the outputs cncel prtilly, the result being the difference between two crdioids which my be shown to be figure - of- eight. By pplying intermedite voltges to one of the diphrgms nd holding the other constnt, it is possible to produce full rnge of ptterns between omni, crdioid, cottge lof nd figure -of- eight. This cn be prticulrly useful in stereo microphone such s the C24 which contins two such cpsules, s it enbles the polr digrm required to be selected remotely once the microphone is in position. It is more difficult to produce vrible pttern F bridge microphone. Electret microphones These re the new bbies. Essentilly they re very similr to the conventionl cpcitor microphone (single diphrgm types) but require no polrising voltge s they hve `permnent' chrge on the diphrgm. An electret is the electricl equivlent of the permnent mgnet, but prcticl electrets hve not been round quite s long, nd less is known bout them. umour hs it tht the `life' of the electret my be s short s three yers for some types; other suggestions re tht they will lst s long s permnent mgnet. This remins to be seen. They certinly offer some ttrctive simplifictions in design, but I suspect tht much remins to be done before they displce conventionl cpcitor microphones. f the two I hve ctully hndled, I would not consider one suitble for nything but domestic efforts t recording pop groups in full by t close rnge, nd the other, climing nd pricing itself for the professionl mrket, seems to lck some of the qulities of its lower -priced conventionl counterprts. But the electret is here to sty, in one sense t lest, nd no doubt there will be improvements in the next few yers tht will increse the output nd reduce the noise. Possibly one of the problems is producing nd mintining sufficient chrge on the diphrgm? Moving -coil In terms of sheer numbers in use, the moving -coil microphone is nd for long time hs been the most populr. It consists of light coil in permnent mgnetic field, the coil being ttched to light diphrgm - rther like miniture loudspeker (fig 13). The unit my be seled t the rer, so tht sound only hs ccess to the front (pressure opertion), or pertures my be provided t the rer to provide phse -shift opertion (crdioid). Unfortuntely it is more difficult to produce good crdioid with moving -coil thn with cpcitor microphone, nd elborte phse shifting tubes, chmbers nd pertures re utilised t the rer of the cpsule to provide resonble crdioid over the frequency rnge; this is prtly due to the mechnics of the moving -coil system, prtly to the higher mss nd mechnicl elements of the moving -coil system. The best moving -coil crdioids re produced with twin element 639 systems but pssble single -element crdioids re lso produced. ormlly, however, the trnsient response suffers s well s the polr nd frequency response, nd the sound qulity of most single element moving -coil microphones does not rivl the cpcitors nd ribbons. Vrible polr digrm moving -coil microphones hve lso been produced, combining the outputs of two bck -to-bck moving -coil elements to dd or subtrct to give omni nd figure -of-eight s well s two crdioids. The dvntges of moving -coil microphones re their robustness nd reltive resistnce to condenstion ( point on which cpcitors fll down), their reltively high output without the need for mssive (nd expensive) mgnet system or hed mplifier, nd the fct tht they cn if necessry be mde quite smll in size (s cn cpcitor mikes). Twin -element dynmic microphones Twin -element microphones re n ttempt to overcome the inherent defects in certin (continued on pge 641) FIG 12 ok FIG ':., DAW I FIGUE B MDE c IFI(i. 13

36 Double system dynmics from A IC I, For dvnced professionl ppliction A.K.G. 202 nd 224 dynmic microphones re so widely used for brodcsting nd sound recording in this country tht most enthusists re well conversnt with their performnce. For those who hve not s yet used either of these models, demonstrtion microphones re lwys vilble without obligtion, fcility which pplies eqully to other models in the A.K.G. rnge. AKG MICPHES re vilble to cover ll possible requirements from domestic tpe recorders to P.A., brodcsting, recording, TV nd film studio use nd re extensively used in these fields. A.K.G. stereo hedphones re lso of high qulity nd competitively priced. AKG EQUIPMET LTD. Erdley House, Cmpden Hill od London, W8 7AS Telephone You tught AUDI DEVELPMETS how to mke mixers by telling us wht ws needed. If you would like to find out wht we hve lernt, write, - telephone, or better still, come to see us the coffee pot is lwys on. Informtion nd quottions re yours for the sking. Fctory : Agent in South Est : HALL LAE WALSALL WD STAFFDSHIE Telephone : Ask for PETE LEVESLEY TECHMAK STATI YAD, BUGH GEE SEVEAKS, KET Telephone: Borough Green 3669 Ask for PETE CXHILL 640

37 MICPHES continued single -element moving -coil systems. ecently revived in the AKG D202 nd its offshoots, with gret success, the principle is not entirely new. In the erly 1930s twin -element microphone ws designed by STC for use on booms in brodcst nd film studios. It incorported moving -coil unit nd ribbon, plus phse correcting nd combining network (fig. 14). The moving -coil unit provided the pressure (omni) component t low nd mid frequencies, but becme progressively more directionl t high frequencies, due to the obstruction of the csing. The ribbon unit provided the pressure - grdient component t low nd mid frequencies, nd its output ws rolled off progressively to mtch the incresing directionlity of the moving -coil unit t high frequencies. This provided resonble crdioid over the udio rnge in the horizontl plne; in the verticl plne the polr pttern nd response were reltively poor, but this ws of less consequence, s the sound normlly rrived from within few degrees of the xis. In the more recent AKG D202 design referred to erlier, the principle is similr to tht of phse -shift single cpsule microphone, but with the udio frequencies split between the two cpsules. The front (smller) cpsule is designed to hndle the higher frequencies nd provide crdioid pick -up with reltively smll coustic phse correction network, nd the rer cpsule hndles the lower frequencies with lrger rrngement of phse nd frequency correcting elements in the tubulr csing behind. The pertures for the sound entering the rer of the second cpsule re set further bck in the hndle thn is norml, s the wvelengths hndled re longer; this hs the effect of improving the output t low frequencies from the rer cpsule, nd incidentlly of reducing the bss rise when the microphone is used close to sound source. For closer look t this microphone, the reder is referred to the recent reviews in STUDI SUD. Despite the fct tht the cpsules re not bsolutely coincident, the microphones produce remrkbly good sound comprble with tht from cpcitor microphones. The polr pttern is well mintined over wide rnge of frequencies nd (gin despite the fct tht four non -coincident cpsules will be involved) the microphones produce very plesnt stereo when crossed. It hs, however, been suggested tht crossed microphones of this kind would not be suitble for coincident qudrphony; in prctice I suspect tht the sheer bulk of four of these microphones would be more of prcticl problem thn theoreticl limittions on the grounds of the distribution of cpsules nd pertures. Crystl microphones Although crystl microphones hve been used for some professionl purposes in the pst, including mesurement nd probe microphones where very smll size ws necessry, they re rrely used now except in domestic equipment. Bsiclly, they operte due to the fct tht when certin crystls re bent or compressed they exhibit the Piezo effect of developing voltges between crystl fces. Like the cpcitor microphone, the source impednce of crystl microphone is lrgely cpcitive, nd requires following mplifier impednce of severl megohms to mintin useful response in the bss. The crystls re inevitbly very stiff; the most efficient microphones hve one corner or end of the crystl fstened to the cse, while the opposite corner or end is ttched to diphrgm (fig. 15); the cpsule cn then behve s pressure or phse -shift device in much the sme wy s moving -coil microphone cpsule does. Most crystl microphones re mde s pressure units, however. ne stereo crystl microphone did pper, using crossed pirs of stggered pressure elements nd the phse shift between cpsules in the pirs to produce directivity through cncelltion off the 'xis' of the pir. Inevitbly there were limittions, however. A less efficient method of generting the voltge, tht resulted in smller cpsule nd hence better response, used pir of crystl pltes cemented to spcer t the edges (fig. 16); the pir behved s pressure - operted device with the crystls bending inwrds nd outwrds with sound pressure; the voltges were smll, however, nd stck of series -prllel connected elements ws necessry to produce workble design, with the mplifier used very close to the microphone. A number of crystl microphones hve in the pst been used in portble outside -brodcst equipment using miniture vlves, for speech purposes only. They were robust, but were not improved by rin which to greter or lesser extent ffects ll crystl mikes (moisture cn dissolve mny of the crystls nd temporrily spoil some of the cermic lterntives). Crbon microphones These re reserved for situtions where intelligibility is undesirble nd provide useful FIG MI (PHASE A ESPSE CECTIG CMPETS MITTED) 641 service in GP telephones where they ensure tht the converstion is protrcted by frequent requests to 'sy tht gin', thus contributing to the telephone deprtment's remrkble profitbility. Use nd misuse of microphones The Editor closed his brief by instructing me to sy something bout how nd how not to use microphones. As if this were not enough, he suggested I refer to the use of ribbon microphones for BBC news -reders which, he lleges, mkes them sound s though they hve tken n overdose of hormone tblets. In fct the bidirectionl 4038 is very good microphone for speech in smll studios s it cn be rrnged to cut out unwnted sounds nd reflections, prticulrly from the tble below it, while not sounding too ded. ne fctor which might be mistken for hormones, in tlks progrmme rther thn in news, is the occsionl unfortunte use of screens. If they hppen to be rrnged with too mny bsorbing fces round the speker, the result is lck of reflected highs but still certin mount of intruding tubbiness from the smll room (some studios re worse thn others, inevitbly); the result cn be very ded nd the speker my be tempted to produce 'bigger' sound. Another fctor with speech on ribbons is tht the microphone my be too close to the speker; inevitbly there is rise in bss nd this cn be compensted for with tone controls. Wht cnnot esily be compensted for is the sitution where the ernest speker lens over to his microphone; inevitbly both level nd the mount of bss chnge. The nswer is to rrnge things so fr s possible tht the speker cnnot move much (without being uncomfortble) or t lest tht such movements s he is likely to mke form only smll prt of the distnce between himself nd the microphone. Another vrible is the script. bviously one discourges reder from plcing the script between himself nd the microphone; not so obviously, the script must be held or plced on rest in such wy tht the speker is not speking into the tble by the time he gets to the bottom of the script. Another 'hormone fctor' is tht very quiet speech mplified to norml speech level sounds more bss), thn loud speech turned down to the sme level. The script tble lso needs some ttention: if it is too hrd, there my be high frequency splsh -bck on to the mike; if it is covered with woolly bsorbent surfce (if only to cut down clunks nd script noises) the effect my be tht the top sounds down. For mny purposes, including tlks nd discussions, perforted tble surfce my be preferble, in order to minimise reflections, prticulrly t low frequencies. Where two reders or only two people in discussion re involved, the bidirectionl ribbon between them gives firly nturl blnce: gin, the lte rrivl who plces himself too fr or too ner is problem. Where severl people re involved in discussion or smll conference, n upwrd fcing crdioid in the middle of the group gives equl pick -up ll round while preventing pick- up of reflections nd noises from the floor (boots hitting shins). With lrger groups, (continued on pge 6.53)

38 WHE YU EED IT WHEE YU EED IT KMAL FL STADS FIE F M FAST! EVEY AGLE KMAL BMS, FL STADS, CLAMPS, ADAPTS, MELDIUM MICPHES, SWA ECKS AD A WIDE AGE F ACCESSIES F ALL USES KEITH MKS (AUDI) LIMITED EADIG AD SUTH, FLEET, HAMPSHIE Tel. Fleet 7316 AUDI T Amongst spekers on demonstrtion in London re the following:- Spendor Monitor, ogers BBC Monitor, IMF Domestic Monitor, IMF Compct, dford Tristr, KEF Cdenz, Dynco A.25 Mk II. Amplifiers:- Cmbridge Audio P.50, P.100, J. E. Sugden A21 / I I nd the otel A 610. Tpe Units:- evox 1108 z trck 71,-/I5 ips nd the ADC 25 nd 10 -E crtridges. The design of the comprtor instlltion, incidentlly, does llow us to interchnge ny mplifier with yours if required, but this service is by ppointment only. LD 9 Dryden Chmbers 119 xford Street London WI Tel: M to SAT AUDI T DEPT. SS M to FI only /5338/8391 PE:M to SAT 10.m. to 6 p.m. DEMSTATI M CLSED MDAY CAMBIDGE Fitzroy Street Cmbridge Cmbridge M to SAT m. to 6 p.m. LATE IGHT FIDAY TILL 9 p.m. ADVICE, CSULTACY SEVICE, DISCUTS, DEMSTATIS, SEVICE DEPATMET, TEST EPTS r,42

39 ûiiiprson; iudo rflicrophones By Angus McKenzie mny yers there hve been gret 1. differences of opinion between engineers s to the merits or otherwise of prticulr microphones in common use professionlly in the UK. It ws felt therefore tht generl ssessment of some well known models tested under idel conditions would be of considerble use to reders, some of whom my be bised unfirly towrds prticulr type or mke where nother type might well be preferble in some respects. It cnnot be doubted tht criteri hve chnged gretly over the lst 10 or 15 yers; with the design of very low noise microphone pre -mplifiers, microphones producing high output for ny given sound level in order to overcome noise present in the front end of some mixers my not be the most suitble tody, prticulrly in pop studios where engineers hve to cope with very high sound pressure levels which my esily overlod microphone pre -mplifiers. It ws decided to check the sensitivity, the noise level, the frequency response, the bility to stnd high sound pressure levels nd the front to bck rtio in the crdioid position of the microphones under test. As result some very surprising mesurements hve been obtined which my well influence reders in their choice. For the sensitivity mesurements the output of ech microphone ws connected vi lod impednce of 1000 ohms to B & K spectrometer type The lod impednce ws step up trnsformer of firly low rtio whose response fter dmping both the primry nd secondry ws mtched within very tight limits from 15 Hz to 20 khz, nd the impednce over this rnge did not vry by more thn +10 per cent. An ccurte nd constnt sound pressure level ws obtined from B & K oscilltor type 1022 with the frequency set t 1 khz with 100 Hz devition wobbulted 16 times per second. A B & K 25 mm free field stndrd omni -directionl microphone ws suspended beside the microphone under test one metre bove the BC 1A loudspeker used for the tests, in such wy tht the microphones were situted to either side of nd equidistnt from the line running through the centre of the three units in the loudspeker. The output from the B & K mike ws tken vi B &K microphone mplifier /sound pressure level meter to the compression input of the 1022 oscilltor nd the tests were crried out t monitored sound pressure level. The figure obtined in millivolts on the Spectrometer ws then relted to 74 db sound pressure level which lso incidentlly represents one dyne per squre cm, or more commonly, one microbr. It will be seen in the tble tht the STC 4136 crdioid cpcitor microphone hs n extremely high output, wheres, s would be expected, ribbons nd moving coils hve the lowest outputs. For the signl to noise rtio of the cpcitor mikes it ws necessry to impednce mtch, trnsform nd mplify very hevily since some of the noise levels were found to be so exceptionlly low. The redings were gin tken on the B & K Spectrometer using the dba weighting curve s it ws felt tht this curve, s well s being the best known in the UK, corresponds firly ccurtely with the subjective difference of noise level lso checked with vrious microphones. It ws found tht these figures tended to expnd slightly the differences between the noise levels of the microphones so tht, for exmple, n SM69 eumnn microphone does not necessrily sound 9 db better thn n AKG C24. Since the figures were dba weighted the vlues quoted re n pproximtion to the equivlent noise produced in the microphone in phons, the reltive scle being the sme s for dbs of sound pressure level. For these mesurements the microphones were plced in turn in B & K nechoic box normlly used for testing hering ids, hving snd -filled wlls nd highly bsorbent nechoic chmber internlly. The box incidentlly ws situted in my studio which itself is triple glzed to eliminte outside noise. Despite these precutions octve nlysis of the noise showed tht occsionlly it ws possible to pick up the rumble from very distnt trffic nd tube trins, sometimes s fr s mile wy, nd I must emphsise tht this prt of the testing ws extremely difficult. Very old twin screened mike cble ws used to connect the microphones to the floting blnced input mplifier s this old cble hd superior screening. Considerble precutions lso hd to be tken with erthing of the equipment to llow the mesurement of such low levels s 17 phons. All the microphones were lso ssessed initilly for pproximte frequency response using the sme technique s for sensitivity but with less wobbultion, the B & K frequency response trcer being used running t slow speed. The microphones were lter ech checked very crefully in n nechoic room under excellent conditions. In order to test whether ny microphone ws subject to blsting or distortion t high sound pressure levels ech ws checked with sound pressure level of pproximtely 130 db pek obtined by my blowing hrd on trumpet only 150 mm wy from ech microphone in turn, the sound pressure level of ech test being checked with the B & K microphone. All the microphones were tested subjectively by listening to speech, nd I hve lso been ble to check the performnce of lmost ll the microphones on recording sessions mde over the lst few yers. Where pplicble the bck to front rtio in the crdioid position ws lso checked in n nechoic room. It ws lso decided to determine the bsic noise level in phons of ll the mgnetic type 643 microphones by regrding very low noise ichrdson Electronics microphone premplifier s n integrl prt of the microphone circuit so tht the resulting equivlent noise could be compred under the most fvourble conditions with the noise produced by the cpcitor type microphones. The trnsistorised microphone pre -mplifier ws fed from three PP9 btteries in series, giving just over 27 volts. Cpcitor Microphones AKG C24 This microphone, introduced pproximtely ten yers go, is stereo co- incident type hving the properties of two mono C12s in one microphone hed. A 20 metre cble hving stnd mount on one end connects to mins power unit, the output of which contins both the udio output wires nd the remote control polr digrm connections to the control box. This box llows ech microphone cpsule to be set independently in ny one of nine ptterns vrying from omni- directionl to figure eight, super crdioid, crdioid nd hypercrdioid, for exmple, being included. A 6072 low noise double triode is used in this microphone s the mplifier for both sections, nd lthough in its dy this microphone ws regrded s one of the finest mde, by tody's stndrds it hs rther high noise figure of 26 phons. As with mny other erlier designs of AKG cpcitor microphones it hs rising response t treble frequencies, this being provided t the request of the BBC nd some Europen brodcsting compnies. The end cpsule rottes through 270 degrees with respect to the other sttic one llowing ny reltive position to be obtined between the cpsules. Some rpid frequency interference hs often been encountered with this microphone, but creful experimenttion with the vrious erthing combintions gin minimises this. AKG explined tht the power supply should lwys be connected if possible vi the mins to mins socket tking its erth from the sme point s the socket feeding the mixer's power supply, this ssisting in the reduction of rf interference. The bss response is very flt with the exception of the figure eight position where the loss is pproximtely 2+ db t 50 Hz. At 10 khz the response rises to pek of 6.5 db flling firly steeply so tht t 15 khz it becomes flt gin. The off xis response follows the sme chrcteristic s the C12A. The bck to front rtio in crdioid is pproximtely 20 db t middle frequencies, deteriorting t low nd high frequencies. AKG C12A The erlier C12 ws entirely redesigned in very much smller housing but with the sme (continued over)

40 STUDI MICPHES CMPAED continued type of cpsule. The originl vlve design ws replced with nuvistor which proved to hve n improved signl to noise rtio. The very noticeble boost t high frequencies of the erlier model ws noticebly reduced to meet professionl requirements, nd prt from the significntly lower output level is very similr to tht of the C12. The noise level is pproximtely 21 db better thn for the C12. Erly smples of nuvistor tended to produce very low level, middle frequency singing which hs not been present in recent models. The power supply hs the polr digrm switching integrlly mounted nd bss cut switch is lso provided with three opertionl positions. The frequency response is very similr to tht of the SM69 but without the ltter's bss roll off, the response extending down to 30 Hz when in the crdioid position. A slight bss roll off ws however noticed for the figure eight position. At 30 off xis the high frequency shelf is not so pronounced, but in crdioid s one pproches 90 pek of 5 db becomes noticeble t 10 khz due to internl reflections inside the housing. The bck to front rtio mesured 20 db, deteriorting t the low nd high frequencies. AKG 412 The nuvistor premplifier in the C12A hs been replced by n FET /P configurtion premplifier with very much lower noise of 21 phons, considerble improvement. The model tested ws n erly one nd further improvement is likely. The response is lmost identicl to tht of the C12A, but the high frequency shelf is only 2 db up. At its price its performnce is considered excellent lthough s with the eumnn U87 I feel tht hypercrdioid position would be very useful. AKG 451/452 The need ws pprent for the production of modulr microphone system in which different types of cpsule could be screwed on vi vrious dptors to either of two types of mplifier. The 451 runs off 10 volts obtined from mins power supply with phntom powering or bttery power supply idelly hving bttery voltge not exceeding 9.4V obtined from single PP3. The 452 mplifier runs off conventionl phntom powered circuit often provided in custom built equipment. A seprte mins power supply is lso vilble for obtining the necessry voltge. f the vilble cpsules the CKI type is crdioid hving n lmost flt response. The CK2 is omni- directionl nd the CK5 hs permnent windshield nd internl nti - vibrtion mount, nd is designed prticulrly for public ddress use, hving lso bss roll -off. The CK6 will shortly be vilble nd includes switching on the cpsule llowing either omni, crdioid or figure eight response to be obtined. The CK9 is rifle type, highly directionl cpsule nd ssembly, hving long tube extending from the cpsule to chieve the directionl properties. A high output CK1 cpsule will shortly be vilble, prototype of which ws tested nd found to hve pproximtely 4 db higher output thn the norml CKI, nd thus very much better signl to noise rtio. In the tests it ws found tht the spred of sensitivity nd hence noise performnce ws rther vrible for the CK5 cpsules, the vritions flling within 4 db in output. With CK1s nd CK2s however this vrition ws reduced to spred of 11 db. The 451 nd 452 hed mplifiers hd identicl gins but the 452 hs slightly lower noise thn the verge 451, the noise spred of the ltter lso being within 1 db. The 451 mplifier contins dc converter using one MHz oscilltor to chieve n dequte polrising voltge, nd hs zener diode incorporting stbilistion from 9.7 volts. Unfortuntely in Austri PP3 btteries, mde by Philips, hve somewht lower voltge under lod thn similr btteries mde in this country. Short circuit current of the Austrin btteries is pproximtely 150 ma wheres the British btteries give out 600 ma. AKG did not relise this nd it is therefore unfortunte tht British btteries give voltge very close to the zener diode regulted one, nd some bttery power supplies tend to crete therefore smll degree of noise in the feed to the mplifier nd cpsule. To obvite this I suggest tht series resistor be incorported into the bttery comprtment to lower the `on lod' voltge to pproximtely 9.2V. A metl windshield type W17 is vilble for the CK1 nd CK2 cpsules. Vrious extr tubes cn lso be provided s well s swivel joint llowing the cpsule to be ngled t plus or minus 90 degrees from norml, this llowing for four microphones to be mounted in very close proximity for qudrphonic recording. The excellent response of the CK1 cpsule mkes this microphone idel when the engineer prefers to lter the response curve on the control desk, nd the modulr construction mkes the microphone very dptble. The off xis response is very similr to tht of the KM84, both crdioid cpsules being of the pressure - grdient type with slots behind the cpsule nd in the body of the microphone giving crdioid pttern. A very steep cut bss filter is vilble nd bttery nd single or double mins power supplies re vilble, nd lso one hving six outlets. eumnn SM 69 /FET As with AKG, eumnn hve now dpted their entire microphone rnge to incorporte FETs in the hed mplifiers. This microphone hd the lowest noise of ny tested (17 phons) nd lso by tody's stndrds high output level. The microphone hs similr fcilities to the C24 with n identicl choice of directivity ptterns, 20 metre hed cble being provided. The pttern switch is incorported in the power supply. eumnn lrge cpsule microphones hve their cpsules suspended both from the periphery nd from the centre, wheres AKG ones re held only from the periphery. The response on xis ws 31 db down t 50 Hz grdully rising to shelf of 31 db t 5 khz, the shelf flling bck to +2 db t 15 khz. This shelf up t high frequencies is intentionl to mke up for high frequency ir losses when the microphone is used some distnce wy from the sound source. The excellent response ws not only held to very tight tolernces between the two cpsules nd from bck to front in the figure of eight pttern, but lso no noticeble chnge in the response shpe occurred t or 60 off xis, mking this microphone quite the most remrkble one ever encountered by the writer. eumnn 1187 This FET equivlent of the erlier U67 hs switching for omni, crdioid or figure eight ptterns, nd s with the SM69 uses 2.5 cm dimeter diphrgms. The smple tested hd lmost the sme low noise level s the SM69, nd lso includes 10 db cut switch incorported into the circuit before the gte of the FET. It ws felt tht good s this microphone is there should be hypercrdioid position which might be in ddition to, or in plce of, the omni- directionl one, llowing the microphone to be of fr more use when used in other thn close miking techniques, thus giving better control of the reverbertion pick up. The microphone is internlly powered, nd incorportes bttery stte indictor, but my lso be phntom powered externlly. A windshield, type WS67, is lso vilble. In crdioid the response is held within 2 db from 200 Hz to 14 khz, bove which it flls very steeply. At 50 Hz, however, quite noticeble bss loss of 5 db is pprent. The frequency response curve remins lmost identicl up to 60 off xis, but t 90 the response flls very shrply bove 10 khz, but hs 4.5 db resonnt pek t 9 khz. The bck to front rtio of this micro- phone ws only 13 db, deteriorting quite mrkedly t low nd high frequencies. It ws felt tht possibly the polrising voltge of the second diphrgm hd not been set ccurtely enough by the mnufcturer, since this type of microphone should hve bck to front rtio better thn 16 db. eumnn KM84 This microphone is the most modern development of the well tried crdioid KM64, nd hs the low noise level of 18 phons. The microphone is phntom powered, nd bttery supply type BS45 or mins power supply type 451 is vilble. A twin mins power supply type 452 is lso vilble to power two microphones. Aprt from 50 Hz 3 db droop the response ws held to within 2 db up to 16 khz, nd ws only 5 db down t 20 khz from verge level. ff xis the bss loss becme very slightly more noticeble nd t 90 the response fell shrply bove 10 khz. eumnn KM 86 When microphone of smller dimensions thn the U87 is desired, but with the sme directivity pttern fcilities, this microphone cn be used. As with the KM84, swivel mount is vilble nd the sme phntom powering supply is needed. eumnn cn lso supply vrious cbles incorporting hed mount dptors of different lengths to meet ll requirements. In crdioid position the response is very similr

41 to tht of the KM84 but slight high frequency shelf of pproximtely 2 db ws noticeble between 8 nd 15 khz, with pek of 31 db t 8 khz itself. The polr response ws lso similr to tht of the KM84. The bck to front rtio ws 20 db from low frequencies up to pproximtely 5 khz reducing to 10 db t 10 khz. This excellent rtio t low frequencies would mke the microphone prticulrly suitble for use in TV studios where rumble behind the microphone would thus be considerbly less noticeble. STC 4136 This pressure grdient microphone obtins its crdioid response cousticlly, nd is phntom powered. The twin power supply is provided with impednce switches llowing either 30 or 200 ohms to be selected. All the tests were crried out in the 200 ohm position. A very high output is obtined; in my opinion fr too much gin being mde vilble. Although the response ws flt nd the noise level reltively low, this model is not suitble for reproducing very high sound pressure levels s considerble blsting nd distortion become progressively noticeble bove sound pressure level of pproximtely 115 db. It is envisged tht group of brss instruments plying close to the microphone might well produce udible distortion, s in the test my trumpet t 150 mm sounded intolerble. Even on norml input signls it is suggested tht the 30 ohm output be used, thus decresing the possibility of the subsequent stges being overloded. The microphone's forerunner, the hd only single FET mplifier nd therefore hd very low output of the sme order s moving coil microphone, nd it is suggested tht the mnufcturers should decrese the gin by the ppliction of pproximtely 10 db more feedbck, which should lso improve the overlod chrcteristics. A little more trouble in the design of the prmeters of the mplifier could hve mde this one of the most recommendble microphones to be tested. This microphone's response is very flt, with excellent hf response off xis. At 90 slight resonnce occurs t 10 khz of 5 db, similr to the C12A. The bck to front rtio is extremely good, being the best mesured for ny cpcitor microphone. Clrec 1050 Avilble lso in modulr construction, this crdioid cpcitor proved to hve good frequency response nd lso very low dba weighted noise figure. However. on ll the smples tested the rumble level produced by the FET used becme prticulrly noticeble becuse the hiss level ws very low. This cused the unweighted noise to mesure rther poorly, lthough listening tests showed the microphone to be subjectively very good. A mrginl corseness ws udible under some conditions, giving sound not quite s good s the AKG 451E, but the noise level ws noticebly superior. Some smples tested hd rther worse rumble level, but I understnd tht this vrition hs now been corrected by the mnufcturer. Dynmic Microphones AKG D 202E1 This model is unusul in tht two seprte crdioid cpsules reproduce the high nd low frequencies. The outputs re mtched nd re pssed through bss cut switch on the body of the microphone. A stnd mounting clmp is provided. The microphone cn esily be hnd held nd is firly insensitive to externl shocks or vibrtion. Aprt from its obvious use s generl purpose crdioid microphone, it hs prticulrly plesing qulity on speech nd is in common use in the continuity studios t the BBC, since it is lso very free from speech popping. The crossover between the cpsules is quite complex, nd occsionlly wire cn become dislodged if the microphone is crelessly hndled, but since this cn be esily resoldered it is not too serious criticism. Although the response on the min xis is held to within 4 db between 50 Hz nd 10 khz, flling rpidly bove 14 khz, off xis the high frequency fll off becomes very mrked. At 30 off xis 10 khz is 4 db down, t 60` 9 db down, nd t db down. The front to bck rtio t middle frequencies is exceptionlly good, being 25 db, this figure only deteriorting to 20 db t 10 khz. However t lower frequencies the rtio is 10 db. Becuse of the off -xis fll off of high frequency response this microphone is quite unsuitble for use s stereo pir, nd for this reson if used in bck to bck crdioid configurtion gives very serious loss of high frequencies on the centre imge, fct well known to professionl engineers who hve tried this technique. Its highly directionl properties t high frequencies, however, mkes it eminently suitble for spotting one solo instrument in group when multi mike technique is used, since such solo instrument will sound more forwrd thn instruments on either side. The smple tested hd dips of 2 nd 3 db respectively t 1 nd 7 khz. AKG D224 This is slimmer stick version of the D202 with very similr chrcteristics, lthough hving slightly fltter frequency response. The ppernce is rther more plesing thn the D202 nd it is therefore more suitble for use in TV or in cses where the ppernce is 645 importnt. The sound produced by speech is of similr qulity to tht produced by the 451E, nd with first clss microphone premplifier the noise level is slightly quieter, lthough hving different spectrl nlysis. The polr response t high frequencies is slightly superior to tht of the D202, but I consider nowhere ner good enough to llow two of the microphones to be used s stereo pir. A bss roll off of 4 db ws lso noticed t 50 Hz. AKG D12 This model hs been vilble for some yers nd is of box type construction with the usul AKG silver nd blck sides. The sensitivity is some 3 db higher thn for the D202, llowing the very low noise level to be obtined of 21.5 phons, noticebly superior to number of cpcitor microphones tested. In order to chieve good front to bck rtio t low frequencies the crdioid response is prtly chieved by cousticl mens in the body of the microphone. This however increses the impednce t low frequencies so tht bss roll off of pproximtely 4 db is noticed t 70 Hz even into 600 ohms input, the bridging impednce normlly recommended for 200 ohm moving coil microphones. Incidentlly, ll cpcitor nd professionl moving coil microphones in the AKG rnge hve source impednce of nerer 150 ohms. This microphone is prticulrly insensitive to shocks nd is probbly the most relible over long period of the microphones tested. Studios hve frequently dropped them with no deteriortion. Although the response extends to 12 khz it is rther more peky thn the more expensive moving coils. STC 4038 Some yers fter the wr the BBC designed wht hs been regrded s one of the finest ribbon microphones ever mde, nmely the PGS, fter mny yers of experimenttion. This design ws tken over by STC who developed the 4038 s result, its chrcteristics being very similr to those of the PGS. Even tody its qulity cn still be regrded s good, nd its velocity directionl properties proved to be very useful in studios. Mny engineers like to use this microphone on different types of instrument, nd the chrcteristic, common to ll velocity sensitive microphones, of boosting bss from sound source in close proximity becomes very useful on occsions. The response is extremely good for ribbon microphone, tiling off bove pproximtely 10 khz. Since the microphone includes n extremely powerful mgnet it should be kept well wy from recording tpes. Although this my be obvious to mny reders, I hve herd of mny trgedies in which msters hve been dmged. The unusully high output from this ribbon microphone mkes it very suitble for simple stereo recording provided very good microphone mplifiers re vilble, but lck of rising top cn tend to mke the microphone sound rther dull. Even t 60' off xis the frequency response remins lmost identicl, giving very precise positioning when two microphones re used for stereo. The response is, of course, identicl on both sides of the microphone. A generl nlysis of ll the subjective nd (continued over)

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43 STUDI MICPHES CMPAED continued objective tests hs shown clerly tht there re considerble differences in noise level between different types of cpcitor microphone. Furthermore, the frequency response t the very low end nd t the treble end re noticebly quite different from one model to nother. It should not be ssumed tht microphone should lwys be s flt s possible s bss roll off cn be prticulrly useful for reducing rumble nd studio boom, wheres high frequency boost is lmost lwys desirble for most purposes, prticulrly when microphones re not in close proximity to the instruments being recorded. Air tends to bsorb high frequencies more thn lower ones over distnce, nd this is the min reson why treble boost ws designed into mny models of cpcitor microphone, lthough by tody's stndrds some of the erlier models took this to excess. In mny cses this boost ws obtined in the cpsule itself, giving rise to slightly worse signl to noise rtio since the effective electricl dmping t these frequencies on the input stge of the built -in microphone premplifier becomes worsened. Insertion of correction network in the microphone led cn not only fltten the microphone's response but decrese its noise level. Mny engineers therefore prefer to work with fltter microphone nd introduce controllble boost in the mixer. which I personlly think is slightly preferble. If no boost is vilble in the mixer, however, on verge more cceptble sound for the mjority of listeners is obtined by hving cpsule with built -in boost. The erlier eumnn SM2 hd much more high frequency boost thn the SM69, nd for this reson mny semi -professionl users not hving tone control fcilities hve found it preferble, lthough the signl to noise rtio is inferior. ther the sme sitution occurs with the comprison of the AKG C24 with the eumnn SM69. Cre must be tken not to tke too much notice of the differences in microphone noise levels below 21 phons or so since even for speech recording noise level below this will be below the norml mbient noise of lmost ll frequencies found even in recording studio conditions. For the recording of music, especilly on close miking, ny microphone hving noise level better thn 24 phons will not be likely to produce ny udible noise. The lowest noise microphones re prticulrly useful when either speech or very quiet sounds re being recorded in n unusully quiet studio hving firly low reverbertion time, or lterntively in situtions where the microphone is being used in very lrge concert hll, such s the oyl Albert Hll, in which the music to be picked up hs n unusully wide dynmic rnge necessitting the blnce engineer to pot up the quietest pssges. Under these conditions the SM69, the U87, the KM84 nd the 412 nd 451E with the high output cpsule, should ll give excellent results. The Clrec 1050's rumble level might unfortuntely become just noticeble. For generl studio purposes the price difference between the AKG 451 rnge nd the fr more expensive eumnn KM84 must weigh hevily, s must lso the modulr dptbility of the 451. The U87 is very fine microphone indeed, nd perhps if potentil nd present users were to demnd it, it could be supplied with my proposed hyper -crdioid position. AKG's equivlent 412 is subjectively only little inferior, hving more middle frequency noise, this being prticulrly emphsised with the dba weighting curve. It is possible tht the 412 will be vilble with remote control pttern selection, thus mking it more dptble thn the existing eumnn. The eumnn, however, hs the dvntge of hving its built -in bttery supply, mking it idel for loction work. The STC 4136 microphone cn only be recommended on occsions where norml sound pressure levels re experienced. 1 hve myself experienced clipping on brss on recent session with this microphone, which ws immeditely replced in the emergency with the D224. n speech the 4136 sounded excellent, but it is worth pointing out tht this microphone is strictly recommended for use into lods greter thn 1000 ohms. To lesser degree this recommendtion pplies to eumnn microphones, their specifiction being 1000 ohms exctly, wheres AKG microphones re quite hppy working into 600 ohms, very often found in prctice. The output level from the microphones lso should be considered in ddition to the noise. A mixing desk hving poor input mplifiers will not only give n unstisfctory noise performnce with dynmic microphones, but even with low output cpcitor ones. n the other hnd, some mixing desks tend to overlod esily or hve distortion level incresingly noticeble from 10 db below the input clipping level. In such cses microphones hving n output level in excess of -60 dbv for one microbr should be used with cution since sound pressure levels of 114 db found quite often in prctice will give level in excess of 100 mv. The nture of the noise itself is importnt nd, with mny types of double diphrgm cpcitor microphone, the diphrgm being held t the sme potentil s the centre becomes lod impednce on the other diphrgm. This will slightly reduce the output from the microphone but will double the cpcitnce pplied to the input of the mplifier nd therefore lter the noise level to one octve lower turnover. Microphones hving this second diphrgm ctully switched off my sometimes sound subjectively lower noise, nd such ws the cse with the well known eumnn U47. A good front to bck rtio is importnt when microphones re used either to spotlight sound in front, discriminting ginst sounds behind, or when rejection of generl studio mbience is desired. In selecting microphones for reverbertion pick up where the crdioids re fcing wy from the sound being recorded good bck to front rejection is gin desirble, llowing high proportion of reverbertion to direct sound to be picked up. For this ppliction bckwrd- fcing crdioids must lso hve n inherently low noise level llowing the reverbertion to be brought up considerbly in level without hiss being udible. For high qulity public ddress work or on occsions where public ddress feed is required from the recording or trnsmission, blnce, good bck to front rtio will considerbly increse the mount of mplifiction 647 tht cn be given to the public ddress speker system without howl round. Should two seprte microphones be required in firly close proximity for recording in stereo cre should be tken to choose models with good high frequency response off xis. nd for this reson the D202 nd D224 should definitely be voided. Almost ll cpcitor microphones lso show reduction of extreme top response considerbly off xis, but it ws interesting to note tht the C12A hd slight boost under these circumstnces. The BBC's choice of these microphones s stereo pir for the oyl Albert Hll Proms this yer ws therefore quite wise since it improved the proportion of high frequencies noticeble in the centre of the sound stge, nd lso the ccurcy of positioning of instruments hlf left nd hlf right. Although the STC 4038 ribbon hs the finest off xis response reltive to tht on xis of ny microphone tested, hiss would most certinly be noticeble t very high frequencies if it were used t considerble distnce from the sound source. emember too tht moving coil nd even ribbon microphones tend to show comb filter effect (mechnicl resonnces) if the response is mesured with very slow sweep with pen chrt recorder running t high speed. This effect found to greter degree in loudspekers is responsible for wht is commonly termed colortion. When considering the choice of pir of microphones for stereo, or group of four microphones for qudrphonics, the method of mounting should be seriously considered. Any obstcle ner the cpsule of crdioid microphone, prticulrly in front of it, such s the body of nother microphone, cn seriously distort the sound field by cusing reflections t high frequencies. ight -ngle bend dptors llowing the four mplifiers to be mounted verticlly grouped together with their cpsules therefore only 6 cm or so prt bck to bck, would give very much less distorted sound field thn one in which the microphones re ll mounted horizontlly in criss -cross fshion with the bck of the body of one microphone being in front of the cpsule of the opposite one. Looking to the future, AKG will be bringing out their stereo equivlent of the 412 to replce the C24, in bout yer. They re lso working on qudrphonic microphone with four crdioids in one microphone hed s further modifiction of the FET version of the C24. eumnn will shortly be introducing, s result of mny requests, n FET version of their old but populr U47. As finl test to prove tht very low noise level could be chieved from moving coil microphone, my children bought some Mexicn jumping bens which mke very quiet clicking noises s the insects inside et the interior of the ben. I plced six of these in n nechoic box together with D12 microphone nd pplied some 80 dbs mplifiction. The resulting sound ws quite stonishing, nd the signl to noise rtio quite resonble under these specil circumstnces. I would like to cknowledge with thnks the ssistnce given by the BBC in helping with some test fcilities. They wish to mke cler tht they do not ccept responsibility for ny mesurements, or conclusions, drwn in the rticle. I would lso like to thnk the mnufcturers for their considerble co- opertion.

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45 kieciny EuerEtHJs Jockey EHtrordr1er!,J By Adrin Hope E of the nicest things bout being in Sussex lst summer ws hving the chnce of picking up BBC dio Brighton on the FM bnd nd hering Kenny Everett's Sturdy lunchtime show. n the Sturdy tht I herd it he ws in fine form, offering bribes to the gentlemen in blue over the ir -'the locl police hve promised not to book me for speeding if I ply them record -so I'm plying them whole LP,' nd then giving out snow wrning for Bnk Holidy Mondy. Everett lives nd works surrounded by fmily, chickens, horse -sized dog nd culdrons of bubbling nettle wine in ner idyllic surroundings. With well equipped little studio christened 'wireless workshop' built into smll room of the frmhouse, nd originl bems poking through the coustic tiles, he relly hs no need to move further field thn the nerest rilwy sttion nd desptch the tpes of his progrmme to whtever locl rdio sttion hs commissioned them. Tht is exctly how he now works. But to strt t the beginning... nce upon time there ws young ld who plyed round with couple of primitive Philips four trck domestics to produce 'lyered' tpes which he sent round the country for the musement of nyone interested. 'I ws so fscinted by tpe,' sys Everett, 'I couldn't understnd why everyone wsn't using it. I still don't know why nyone ever buys disc.' Sure enough, discs re surprisingly thin on the ground in his studio. Just few ll -time fvourites (like the erly ilsson recordings) nd pile of current choices. A clue perhps to the cretive content nd the success of his progrmmes is his comprtive lck of involvement in the current music scene. 'I get records, but I usully give them wy.' Bck in the erly 1960's someone on Tpe ecorder, s STUDI SUD used to be, suggested tht he send tpe to the BBC. He did, nd the tpe ended up in the hnds of Wilfred D'Eth, who recently cme into the public eye by luring Dphne du Murier in front of TV film crew for the first time. D'Eth brodcst the tpe before leving BBC rdio nd in some wy or nother the pirte sttion dio London cquired copy. As more or less direct result, Kenny Everett strted two nd hlf yer stint with tht ship nd mintins tht he loved every moment of it, not only through the mists of nostlgi. Possibly this ws becuse he left six months before the legl guillotine fell. He quit for vriety of resons. For instnce, he felt tht the pirtes, still relying on virtully 100 per cent needle time nd with obviously no hope of ever moving on to lnd, hd by then plyed themselves out. There ws no sign of the gret British listening public downing their pthy bout lnd -bsed lterntives to the BBC. He further believed tht before very long dozens of ex- pirte disc jockeys would be knocking on the doors of Brodcsting House looking for legl jobs. But despite this shrewdness, things didn't quite work out the wy they might hve done. Everett only strted regulr brodcsting with the BBC some six months A (After dio ne), probbly becuse of his firly open criticisms of the wy the BBC hd until then hndled its disc jockey progrmmes. Wheres in Americ nd Austrli -nd t the pirtes - it ws trditionl to hve one mn plying the records, doing the cht nd working the controls, the BBC hd lwys used whole tem. Along with everyone else who hd served n pprenticeship on the pirtes, Everett knew tht the only wy you cn run fst progrmme is to dopt one mn driver technique. Eventully the BBC esed him into brodcsting, nd the rest is more or less history. His Sturdy show won him criticl cclim, fme nd possibly little fortune. It is lso history tht he ws scked yer or so go in blze of publicity, supposedly for commenting over the ir on news bulletin. In his view, the rel reson for the scking ws tht for long period of time he hd nswered Fleet Street reporters honestly when they sked him wht ws wrong with dio ne. After the BBC cme mss of publicity which, hd locl legl commercil rdio been redy to go, would hve erned him fortune. As it ws, he went briefly into Luxembourg nd the short -lived dio Monte Crlo British trnsmissions. He is still bnned in the most forceful wy from Brodcsting House but, by curious mbiguity, the locl sttions re ble to employ him. Which is how I hppened to her him on dio Brighton. (continued over) 649 Kenny Everett in his 'Wireless Workshop'. The mixer is detiled overlef.

46 KEY EVEETT continued The progrmme I herd ws put together (like everything he does) in his `wireless workshop'. The bsic equipment is Gtes Crtridge Mchine with record mplifier nd Astronic Equliser, two Pye compressors, I chnnel mixer with echo nd tpe remote controls, two EMI BTJ, evox nd Gtes turntble with Grey rm. ther surprisingly, he uses only one turntble nd so, fter ech disc plyed, stops to edit. Plybck monitoring is on Qud 303 through couple of EMI speker units built into tilor -mde cbinets. These -nd everything else -were put together by Mike Howell, who used to be pirte technicin. ot surprisingly, the whole set -up is rther like lndborne pirte ship. It ws on the pirte ships, with hours to spre between progrmmes nd not much else to do, tht Everett perfected his present techniques of jingle production. Some BBC locl sttions commission him to do jingles lone. The wy he does them is interesting. The strting point is ny one of his pile of copyright -free discs. Hving picked trck, Kenny spends hours fitting suitble words to the music. Like references to the sttion involved, the wvelength nd `wht fun sttion it is, lthough usully they ren't'. He then uses the two BT4 in to- nd -fro mnner to dd on severl voice hrmonies (usully four) nd possibly n over -the-top spoken voice. 'l'he finl result then goes on to continuous loop crtridge of the type used by the BBC, with compression to keep the trnsmission stff hppy. The crtridges used re the norml type, comptible with the BBC ol- Plessey mchines which use loop running t 19 cm /s with udio on one trck nd cue pulses on the other. Everett uses the Gtes instnt stop -strt mchine becuse he prefers it to the ol- Plessey. Hving herd bit of dio ne recently, the number of times the disc jockeys hve trouble with their jingles does mke me wonder bout either the jockeys or their mchines. The finished product, either jingles lone in crtridges or whole 38 cm /s progrmme tpes, re sent off with PS lists to the sttions involved. They go three dys erly so tht the sttion mngers cn ensure nothing nughty is being sid. Wht mkes Everett's rdio progrmmes cut bove the rest? Prt of the nswer is obviously his reputtion of being not exctly mn to ply sfe (one might sum him up s being bit of boundry nudger). But there is whole lot more to it thn tht. Working on the ssumption tht disc jockeys re necessity (becuse, Everett clims, simply plying whole LP's over the ir hs been tried in the Sttes nd just doesn't work), there seem to be two types of DJ tht re worth listening to. n the one hnd there re those like Aln Dell, who ply music either with very little cht or with only hrd -core informtive cht. And then there re the `cretive' disc jockeys who put out progrmme which lmost incidentlly uses discs. Come to think of it, I cn't think of ny DJ other thn Everett who relly succeeds t this end of the line. In between there's the ego- tripping rest who re best forgotten. All of which tkes us bck to Everett's comprtive lck of involvement in music for music's ske nd n lmost obsessive involve- ment in using tpe cretively. So it doesn't come s ny surprise to find tht, of ll the medi, he prefers rdio, nd regrds it s grossly neglected nd unexplored. He hs done plenty of TV work but on the whole he htes it. `There is no spontneity on TV. You work ll dy on the studio floor getting redy for tke. After hours of fiddling round with the lights nd your mke -up, they try tke nd you do something good. But it turns out tht the tpe is broken or something hs blown up nd they sk you to do it gin. How cn the result ever be spontneous?' Everett hs fscinting collection of tpes from brod, mostly Americ, instncing wht he sees s best in the mss of good, bd nd terrible rdio brodcsting being put out ll over the world. I ws interested to her one of his tpes, very relxed FM stereo progrmme put out in Los Angeles. I sy interested becuse, by his own dmission, Everett's re `nerve -endy type progrmmes' -the very opposite of relxed brodcsting. He hs been criticised for overlooking the vlue of silence. This dtes bck to the indoctrintion of two nd hlf yers on dio London. The pirte Bible hd n extr commndment to the effect tht on no ccount shlt ny brodcster ever leve puse. Like plenty of people in his position nd with his prticulr type of tlent, Everett is not n esy mn to interview. Tht is not to sy tht he is unfriendly or loof -he is just the opposite -but nyone with his exubernce is lmost by definition surrounded by defensive shells nd disguises which only occsionlly fll wy in the presence of n outsider. But still lot cme through. I sked him bout the future; where he sees himself brodcsting nd in wht style. He hs more fith thn I in the bility of the locl commercil sttions (legl) to improve the generl picture. With locl brodcst dvertising rtes fr less thn on Luxembourg there will no longer be ny need to crm the bsic essentil dvertising informtion into such short spce of time -`the 15- second jm commercil'. Insted, nd for the sme money, the dvertiser will get 30- second or even one -minute commercil brek in which greter cretivity cn ply prt. After ll, in 15 seconds there is room for little more thn the nme of the jm. But with reltively few progrmmes to do t the moment, Kenny Everett dmits to his still hving sense of urgency. I wnt to crm s mny goodies s possible into the only progrmme time vilble,' he sys, `nd I wnt to show wht I cn do'. Whether more progrmmes nd more brodcsting time will men less urgency nd more relxed ttitude, nd whether the finl result will be improved or degrded by slower pproch, remins to be seen. For hopefully he must sooner or lter get more progrmme time to work with. Whtever hppens, I somehow cn't see Everett putting out boring progrmme. Like ll cretive people, he mkes mistkes nd does things tht don't come off, but he is never boring. Unfortuntely with tht Brodcsting House bn ll too obviously in opertion t the time of writing, nd with locl commercil rdio still rther pie -like in the sky, the only chnce of hering one of the true originls in British rdio is to wtch your locl BBC rdio sttion schedules like hwk, nd pounce ccordingly. When I left him he ws in the throes of sending letter off to ech locl sttion mnger offering them some tpe - recorded ction. `Do not dely too long,' he wrned one of them, `these tpes re set to uto -destruct fter few dys'. As I drove home I put on the cr rdio to her, between couple of disc jockeys shmelessly plugging their own terrible records nd plying the sme old jingles, gentlemn with soft Irish ccent nd dily two -hour progrmme dmit tht he hdn't the vguest ide wht `phsing' ws.

47 Equipment eviews KEITH MKS MICPHE STADS WHAT re the qulities one looks for in good microphone stnd? The following points re suggested nd it is by these stndrds tht this review is written. It should be stble, robust, esily nd smoothly djustble. It should be ble to ccommodte ll types of microphone. It should provide good sound insultion from noises vi the floor. It should be elegnt nd, if needed in conjunction with cmers, should hve n nti -flsh finish. It should be esily trnsportble nd resonbly priced. The stnds submitted for review by Keith Monks rnge from the bby MS /S to the MS /L. The stbility of the stnds ws checked in the following mnner. Ech stnd ws djusted to its mximum height nd its boom djusted to mximum horizontl spn directly over one of the legs of the stnd. This is the correct wy to direct the boom for mximum stbility. A grdully incresing force verticlly downwrds ws then pplied to the end of ech boom. With some stnds used in this wy, the boom turns bout its pivot before the stnd tends to topple. With others, the stnd tends to topple first. All the booms tht turned before toppling did so quite slowly, giving resonble wrning to the engineer setting up. It could, however, be trumtic experience to sit in the control Below: BS /t ight: MSP /A room wtching pir of bck -to-bck crdioids descending slowly over the conductor's hed. Ech boom ws then turned to bisect n ngle between its legs. The downwrds force necessry to cuse instbility ws gin mesured t the end of the boom. Stnds would not normlly be used t their extremes but mistkes cn be mde nd it is better if they re not too costly. Severl of the boom rms supplied with the Keith Monks stnds re interchngeble. For the purposes of this review, ech stnd ws fitted with the rm recommended by the mnufcturer. Better comprisons of the stbility of the stnds themselves re given by the product of the length of the boom rm nd the force required. Where equilibrium ws broken by toppling, this product is given in the column heded 'moment'. BS /1 This is treble stnd with cst bse which cn be used in two positions: upright or t n ngle. The review model ws in luminium nd would be suitble for use with cmers. As cn be seen from the photogrph, it would be idel for newsreder s there is dequte room for notes between the stnd nd the reder. The stnd is well mde, robust nd stble enough to hold even the heviest microphone sfely. At 5.50 it is considered excellent vlue for money. BS /2 This is the big brother of BS /1 nd would be n idel tble stnd for speker stnding 651 up; just right for public speking. It is similr in style nd qulity to BS /1 nd t 6.75 is still considered excellent vlue. MS /S This is the bby of the floor stnds but is very sturdy nd esily set up in n emergency. At 6.75 plus 5 for the boom, studios might well consider hving couple hndy for use when n extr microphone is needed quickly in crowded sitution. The stnd nd boom re in chrome nd well finished. The clsp for the rm is efficient nd esy to use. MS /M This stnd looked better thn the MS /S nd is more robust but the screw threds on this prticulr model were rough. Screwing nd unscrewing the legs ws unplesnt nd sometimes tricky. When the height djustment ws ttempted, the extension tube fell out through the bottom of the stnd. The boom rm supplied for use with this stnd ws the lest stble of those tried nd is not recommended s it required two hnds to djust. This stnd with BA /S would mke slightly cheper nd more stisfctory combintion. MSP /A This is n unusul nd useful stnd. Its toggle ction mkes it possible to plce microphones in positions tht might be very difficult with ordinry stnds. It is esily nd smoothly djustble though cre must be tken, s with the MS /M, not to let the extension tube fll down inside the stnd if djustments re mde without microphone ttched. The model supplied hd n nti -flsh finish nd ws robust. The legs did not screw in nd out very smoothly nd it ws found difficult to persude the thred on one of them to engge properly. The stnd ws tested for stbility with ll the upper prt of its length horizontl. The results show it to be remrkbly good. Becuse of its unique ction, it is very useful stnd nd is highly recommended. MS /L with BA /L This is the most impressive combintion in the rnge. With stnd 183 cm high nd boom 162 cm long, it is useful intermedite between the usul portble stnd nd boom nd the lrger ones found in most studios. The stnd hs four screw -in legs nd, closed down to its minimum length of 106 cm, is esily trnsportble. The boom is in one piece nd would not therefore fit into the boot of even lrge crs but could be crried hppily in vn. The boom djustment ws found to be little jerky, but otherwise this stnd nd rm fulfil (continued on pge 653)

48 FACIS F STEATHAM DECKS WITH PE -AMPS (Microphone extr) Aki 8 Tr. Crtridge C.800 Aki 4000D Stereo Brenell Mk. 6 Stereo Ferrogrph 702/4 Philips sp. 4 Tr. Stereo evox 1102/4 2 sp. Stereo Shrp D 712D 3 sp. 4 Tr. Stereo Sony 366D 3 sp. 4 Tr. Stereo Sony 630D 3 sp. 4 Tr. Stereo Sony 266D 3 sp. 4 Tr. Stereo Sony 255 Stereo Tndberg Tr. Stereo Tndberg 3000X 3 sp. 2/4 Tr. Stereo Tndberg 6000X 3 sp. 2/4 Tr. Stereo Telefunken sp. 4 Tr. Stereo Telefunken 203 Studio MAIS SPL ECDES Aki 1710L 2 sp. 4 Tr. Stereo Aki sp. 4 Tr. Stereo *Brenell Mk. 6 *Ferrogrph 713 Ferrogrph 722/4 Grundig Tr. Mono Grundig TK Tr. Mono Grundig Tr. Mono Auto. Grundig TK248 2 sp. 4 Tr. Stereo Philips Tr. Mono Philips Tr. Single Speed Mono Philips sp. 4 Tr. Mono Philips Stereo sp. 4 Tr. Philips Stereo Cssette 2401 Auto. Philips Stereo Cssette 2400 Philips sp. 4 Tr. Stereo * evox 1222/4 Stereo Shrp sp. 4 Tr. Stereo Shrp sp. 4 Tr. Stereo Sony sp. 2;4 Tr. Sony sp. 4 Tr. Stereo Sony sp. 4 Tr. Stereo *Tndberg 15 2 or 4 Tr. /3 sp. /Mono *Microphones extr *Tndberg sp. 2!4 Tr. Stereo *Telefunken M207 2 sp. 4 Tr. Stereo Telefunken 203 Stereo /Mono 2sp. 4 Tr. Telefunken 201 Mono 4 Tr. *Uher Tr. Mono *Uher oyl de Luxe 4 Tr. 4 sp. St. *Uher Vricord 263 Stereo *Uher Tr. 2 sp. Stereo MAIS CASSETTE MDELS *Philips H882 Stereo Tuner /Amp/ Css. *Sony HST399 Stereo Tuner /Amp Css. Sony TC 330 Stereo Css. /Spool * Kellr Dolby Stereo *nk Whrfedle Dolby Stereo Philips 2400 Stereo Philips 2401 Autochnge w. ski -slope *Sony TC 127 Deck nd Pre -mp *Sony TC 122 Deck nd Pre -mp *Philips 2503 Deck nd Pre -mp BATTEY MAIS CASSETTE Philips 2204 Sony TC. 80 Philips 2205 Sony TC. 100 Sony TC. 60 Philips TT 392 with AM 'FM Philips 290 with AM Sony CF 100 with AM /FM Sony CF 200 with AM /FM BATTEY CASSETTES Philips EL3302 Sony TC. 40 Philips 2202 Shrp 418 Sony TC. 12 Grundig C.200 BATTEY SPL MDELS *Tndberg Series 11-2 Shrp Tr 2 sp (BM) Sony TC. 800 B 2 Tr 4 sp (BM) Telefunken Tr 2 sp Uher 4000L 4 sp 2 Tr *Uher 4200/ sp Stereo F A FAI AD DEPEDABLE DEAL I TAPE nd III -FI ITEEST SEVICE CHAGES H.P. UP T 18 MTHS Free Service during Gurntee period Fir Prt Exchnge Allownce on your old ecorder * econditioned ecorders vilble to personl shoppers only AMPEX TAPE FFES (P- Polyester: M- Mylr: A- Acette) Compct Cssettes C.60-53p; C.90-75p; C.120 -El.05 (pp 3p ech). 7" D.P ft. (P)... El.50 7" L.P ft. (P)... Eros SU I.P ft. (M) p sr L.P ft. (A)... 75p sr Stndrd 850 ft. (A)... 63p 5" D.P ft. (P) p S" L.P. 900 ft. (P) p 5" Stndrd 600 ft. (P) 50p 3" reel polyester tpe, 600 ft. (P) 25p Postge on orders under E3 dd lop, orders over E3 sent post pid U.K. Splicers, Defluxers, Bulk Ersers, Accessories of ll kinds. MIXES by Uher, Egle, Sony, Grundig, etc. MICPHES by AKG, Grmpin, eslo, Acos, Beyer, Sennheiser, Telefunken, etc. HEADPHES by AKG, ikko, Philips, Koss, Egle, TTC, Beyer, Aki. MUSICASSETTES. All leding mkes. Pre -recorded 8 -trck crtridges nd tpes. ecording tpes nd cssettes -All leding mkes. III -FI DEPT. AMPLIFIES Qud, ogers, Aren, Philips, Goodmn, ikko, Armstrong, Lek, Tripletone, Tndberg, Teleton. TUES Qud, ogers, Lek, Armstrong, Tripletone, Aren, ikko, Goodmn, Huldr. LUDSPEAKES Qud, ogers, Kef, Whrfedle, Goodmn, Tnnoy, Lowther, Lek, Tndberg, Aren, Celestion, Kelestron. MTS, PICK -UPS GAAD inc. S.P.25 Mk. III Goldring BS Connoisseur Thorens Audiotec Shure et Sonotone Acos SME Dul Pickering Dimond styli, Microlifts, Pressure Guges, Clening Accessories, Cbinets, etc STEATHAM HIGH AD, LD, S.W.I6 Between St. Leonrd's Church nd Strethm Sttion : Plese note this is our only ddress. Free prking Prentis od, 2 mins wy PE ALL DAY SATUDAY- CLSED ALL DAY WEDESDAY EST. 12 YEAS BAD EW- SUITABLE F ALL MACHIES ECDIG TAPES & CASSETTES ALL TP QUALITY 100 " TESTED BY SUPEI AMEICA AD BITISH MAUFACTUES GEEUS QUATITY DISCUTS BASE -TESILISED PLYESTE nd PVC EXTAS - CHAGE -FITTED LEADES EX 3" FEE LL F LEADE WITH ALL TAPE DES 24 HU DESPATCH SEVICE St'rd Ply Long Ply Double Ply Empty Spools 3" 150' 10p 210' I I p 320' 20p 4p 4" 300' 20p 420' 24p 550' 30p 9p 5" 600' 30p 900' 40p 1200' 56p lp 5u' 900' 37p 1200' 49p 1800' 78p lip 7" 1200' 44p 1800' 64p 2400' 95p 12p 3" nd 4" APPX LEGTHS CASSETTES MAUFACTUED by EMI MASTETAPE ALL I PLASTIC LIBAY CASES C60 EMI PLAYITE 34p 3 for LI Ip C90 MASTETAPE 50p 3 for LI 45 P/P C120 MASTETAPE 65p 3 for LI 90 on ll orders If ny goods re found t fult in ny wy money refunded in full. SPECIAL FFE -EMI AFIC LW ISE EEL TAPES nd PE -ECDED CASSETTES AT LESS THA HALF PICE CALLES WELCME WALKES 16 WDTHPE AD, ASHFD, MIDDLESEX ASHFD hi-fi ni1mws A record review A Unk House Group Publ,ction. Ars You too cn be woofer lover. Lich month Hi -Fi xs crries the ltest news, views nd ides in the field of Hi -Fi. Plus some 30 pges of record reviews nd music fetures covering Bch to Atomic ooster. ovember's issue lso tells of the recording of the ' Symphony of Thousnd' in Amsterdm. It reports on the Europen Hi -Fi shows nd gives some useful hints for wll mounting your equipment. It's ll in ovember's Hi -Fi ews nd ecord eview. n sle t ewsgents now. 20p.

49 KEITH MKS EVIEW continued most of the requirements lid down. Hving four legs, the stnd could wobble on floors tht were not level, lthough this did not occur on test. Presumbly most plces where stnd like this would be used would hve level floor nywy. The stnd nd boom re very sturdy nd inspire confidence in use. They re elegnt nd firly esy to djust. There re few esily trnsportble stnds vilble high enough to be of use when recording orgns. In this price rnge, it is quite remrkble to find one tht will do this. This stnd nd boom represent quite remrkble vlue for money nd re highly recommended. A rnge of thred dptors is vilble for ll the stnds, to ccommodte lrge vriety of microphones nd fittings. An interesting ttchment is the clsp which, when fitted on the tube of one of the stnds, enbles n extr microphone to be mounted there. Used with MS /L nd BAIL, two microphones could be quite widely spced using the one stnd nd boom. one of the stnds supplied hd nti -rumble feet, though these re esily improvised with plstic fom. MS /C This stnd llows singers close to the microphone without their kicking the bse. It performs this function well, hs n nti -flsh finish, nd is resonbly stble. Difficulty ws experienced in screwing nd unscrewing the dptor on the extension tube. The thred on this tube ppered soft on the review smple. MS /CT/2 This stnd is robust, well mde nd elegnt. It is well suited for use on stge nd is considered good vlue for money. SBf1 This stereo br is well mde nd thickly chromed but is rther hevy nd should there- fore only be used with stble booms or with the boom upright. SC /1 This side clsp, s mentioned elsewhere, is n extremely useful ttchment. It is well mde nd does its job esily nd is highly recommended. Just s I completed this review, nother boom rm ws sent for exmintion. This hs the excellent ide tht the counterweight screws off one end nd on to the other, thus exposing different threds for the microphone fitting. Unfortuntely the clsp on this stnd ws not very positive nd equilibrium ws broken by pulling t 0.5 kg. It is pity tht such n excellent ide should be spoilt in this wy. Keith Monks Ltd were contcted bout the criticism in this review nd stte tht they hve now included stops in the stnds to prevent the extension tubes flling out when being djusted without microphones fitted. John Shuttleworth Stnd nd boom MS /S & BA/S - MS /M & BA /M Stbility in best position 2 Boom turned (Kg) Stnd toppled (Kg) -- 1 Moment Best Worst (Kg) (Kg) Good Ese of Adjustment Vlue for Money Excellent 0.75 Poor ot recommended - MS /M 3.5 Good á BA /S Averge - MSP /A Averge Excellent MS /L Averge Excellent & BA /L BS / Good -- Good Excellent Excellent - BS /2 - Brnd X Excellent Good Brnd Y Excellent Poor MAUFACTUE'S SPECIFICATI BS /1 30 to 55 cm high stnd, luminium finish, 2 kg weight, 5.50 BS /2 46 to 82 cm high stnd, luminium finish, 3.1 kg weight, 6.75 MS /S 91 to 153 cm high stnd, chrome finish, 3.1 kg weight, (Accepting BA/S.) MS/M 91 to 175 cm high stnd, chrome finish, 4.63 kg weight (Accepting BA /S or BA /M.) MSP /A 130 to 210 cm high stnd, luminium finish, 3.54 kg weight, MS /L 106 to 183 cm high stnd, chrome finish, 6.2 kg weight. 13. (Accepting BA /L.) BA /L 162 cm boom, chrome finish, 2.2 kg weight, 8. (To fit MS /L stnd.) MS /C 96 to 155 cm high stnd, 4 kg weight, (Accepting BA /C.) SC /1 Side clmp Distributor: Keith Monks (Audio) Ltd, eding od South, Fleet, Hmpshire. MICPHES continued where spekers tlk t different levels or where the microphone is to pper in shot, severl smll microphones my be preferble to one centrl one. To complete our ctlogue of microphones nd uses it might, however, be worth putting down one or two points tht get overlooked, nd which don't hve to ffect the wy you blnce music session. Instruments nd singers tend to sound both more relistic nd more plesnt if the microphone is in front of rther thn over them. It is frequently necessry for prcticl resons nd to void udience noise to rise the microphone somewht, but this should not be tken to extremes, especilly with close microphone. Violins nd tenors sound horrible from bove (except where the tenor is singing to his loved one in the Gods) nd some singers re not improved by hving the micro- phone plced so fr below tht it is in direct line with the nose; clrinets, oboes nd to lesser extent brss lso do not tke kindly to microphone looking up the bell. ne normlly hers the instrument from in front so it is not bd ide to record it tht wy. In the sme wy pinos nd hrpsichords sound better without the senstion of being poised where the lid my descend to end one's troubles. Hnd microphones, whether for pop music singers or interviewers, re best chosen to be omnidirectionl. There is less of bss rise problem to contend with, you don't hve to keep on xis so crefully, nd hndling noise is much lower thn with directionl microphones, s explined erlier. Some moving -coil nd cpcitor crdioids re better thn others s regrds hndling noise, prticulrly if they hve bss cut switch to remove both bss nd rumble before they cn cuse intermodultion in the mike mp. In generl the omni is more suitble nd the ribbon the worst for hndling noise. Cpcitor mikes with power coming up 653 the cble must hve good connections nd ttention to the erthing if DC is drwn through the screening brid -potentilly cuse of ferful noises if it is crrying dc. Since I hve to end this somewhere, my I leve reders with the point I hve mde before in these pges, nd which I think DK ws mking in the September editoril: wht most of us strted in this lrk for ws the music. If it ll sounds wrong, put wy your mikes nd buy ticket for live performnce. Better still, do some performing. A perfect nd uplifting performnce is rre, but when it comes no udio system on erth will do it justice or ever cpture completely the sheer exhilrtion of mking, or hering, gret performnce live. A relly good recording or brodcst cn be n extension of one's memory nd the rnge of one's hering: tht is their justifiction. Anyone who believes tht recorded sound will ever completely displce the live performnce, even in populr music, is either fool or no lover of music.

50 Clssified Advertisements Fnfre ecords. Tpe - disc pressings, demo's, msters, ny quntity. Studio /mobile. eumnn disc cutter. S.A.E. brochure. 1 Broomfield Close, ydes Hill, Guildford. Telephone County ecording Service, Demodiscs, mono nd stereo pressings. 7" vinyl discs pressed on our own plnt, delivery pprox dys. S.A.E. for leflet nd price list. Tel. Brcknell London od, Binfield, Berks. Advertisements for this section must be pre -pid. The rte is 6p per word, minimum 60p. Box os. 20p extr. Semi -disply 3.00 per inch. Copy nd remittnce for dvertisements in JAUAY 1972 issue must rech these offices by 8th VEMBE 1971 ddressed to: The Advertisement Mnger; Studio Sound, Link House, Dingwll Avenue, Croydon C9 2TA. TE: Advertisement copy must be clerly printed in block cpitls or typewritten. eplies to Box os. should be ddressed to the Advertisement Mnger, Studio Sound, Link House, Dingwll Avenue, Croydon C9 2TA, nd the Box o. quoted on the outside of the envelope. The district fter Box o. indictes its loclity. Americn ecording Studio, bsed in hio, hs severl originl U.S.A. Msters, which they re willing to lese for relese in Europe. For further informtion write to Box o recording nd trnscription service Vinyl pressings nd cette demodiscs. Limiting, compression nd equlistion fcilities: high undistorted cult ng levels with feedbck cutter heds. Booklet vilble. ST. MICHAEL'S, SHIFIELD AD, SHIFIELD GEE, EADIG, BEKS. eding (0739) Member A.P..S. F SALE -TADE Lncshire. Tndberg, Ferrogrph Tpe ecorders, etc. Plus over 10,000 high fidelity systems. After -sles service. Holdings Photo - Audio Centre, Mincing Lne, Blckburn BBA 2AF. Tel /6. Copyright Free Sound Effects Discs. 7" E.P's nd 12" L.P's. Ctlogue from pid ecording Services, 21 Bishops Close, London, E.17. If qulity mtters consult first our 105 -pge illustrted Hi -fi ctlogue with technicl specifictions (60p). Members enjoy unbised dvisory service, preferentil terms. Membership (40p) p.. ur ssocites lso mnufcture records from your own tpes, or record the Mster t our studios (Steinwy Grnd). Bulk terms for choirs, fund -rising. Plese specify requirements. Audio Supply Assocition, 18 Blenheim od, London, W.4. Tel Professionl tpe only 35p. 1200ft. Agf on hubs, no joins (p. & p. one box 20p, ech dditionl box 8p. We hndle 99 % of ll s/h professionl recording equipment. Send for list. Jckson Studios, ickmnsworth, Herts. Tel. ickmnsworth UIMIXE 4S Mixing unit for professionls in studio nd on loction. (I stereo pir nd 2 pn controlled mics.) Any input imp ohms. S/n rtio greter thn 55 db with n input signl of CV t 200 ohms or 70.tV t 30 ohms. Individul test certificte. Price L45 plus freight. ecent reviews from leding hi -fi mgzines vilble on request from: SUDEX LTD 18 Blenheim od, London, W4. Tel Complete 805 utfit including cse. orm price 250. Specil offer 180. Sennheiser MD211 Microphone, new nd boxed. orm price 44. Specil offer 32. AKG D109 Microphone, specil offer 9. AKG D119C Microphone, specil offer 12. J. J. Frncis (Wood Green) Ltd., 123 Alexndr od, Hornsey, London,.8. Tel AC MIXES Join other stisfied customers. Build mixer using our printed circuit modules -prices from L1.75. r let us custom build unit to your exct requirements -sk for quote. Export enquiries welcome. UGBY AUTMATI CSULTATS 220 ALWY AD, UGBY Fders. Limited quntity, 600 ohm constnt impednce qudrnt, type EM2. Jck Strip Assemblies. P.. type 520 B.P. boxed complete. Advnce Signl Genertor Type H.1. For prices nd detils: Sonifex Sound Equipment, 93 Stnwell Wy, Wellingborough, orthnts. Telephone edwells Sound Mintennce Co., 179 Torridon od, London, S.E.6 ( ). We specilise in monitoring equipment for the smller studio. Qud ELS, ogers BBC Monitor, nd Spendor BC1 on permnent demonstrtion. Bring your own tpes if you wish. Good prking fcilities. 9.m. opening to 6 p.m. (Mondy, Tuesdy), 8 p.m. (Wednesdy, Sturdy, 1 p.m. (Thursdy) nd to 9 p.m. Fridy. STUDI FACILITIES Your tpes to disc. 7" , 10" L.P. 3.50, 1" L.P dy postl service. Msters nd Vinylite pressings. Top professionl qulity. S.A.E. photo leflet: Deroy Studios, High Bnk, Hwk Street, Crnforth, Lncs. J & B ecordings. Tpe to disc -ltest high level disc cutting, ll speeds. Mstering pressings, studio, mobile. 14 Willows Avenue, Morden, Surrey. MITchm Grhm Clrk ecords. Tpe to disc pressings. P. F. A. House, 182A Sttion od, Addlestone, Weybridge, Surrey. Tel. Weybridge MISCELLAEUS Tpe nd Cssette ecorder epirs by Specilists. The Tpe ecorder Centre, 82 High Holborn, London, W.C.1. WATED Lee Electronics. The Tpe ecorder nd Hi -Fi Specilists wish to purchse good qulity Tpe nd Hi -Fi equipment for csh. 400 Edgwre od, W.2. Phone PAD Highest possible csh prices for evox, Ferro - grph, Brenell, Vortexion, Tndberg, Aki, B. &., Snyo, Sony, Uher Tel Complete ecording Studios purchsed for csh. Also ll types of Professionl ecorders nd ssocited equipment. J. J. Frncis (Wood Green) Ltd., 123 Alexndr od, Hornsey, London,.8. Tel Professionl nd qulity tpe recorders nd ccessories, lso hi -fi equipment purchsed for csh..e.w. Audio Visul Co., 146 Chring Cross od, W.C.2. Tel /8 Upper Tooting od, S.W , Studio ccommodtion pprox. 600 sq. ft. Any condition considered. Southend re. Phone Southend evenings. F SALE -PIVATE Professionl Mobile Discotheque. Vortexion, evox, Thorens, Shure, Beyer, Grmpin, Tnnoy, B. &.; ecords, Tpes. All extrs. Cost over 950-sell 450. Further informtion Hornden 3998 (Hnts). AKG C12A studio microphones. Two only, brnd new nd boxed, t 150 the pir or ner offer. Tel

51 off F SALE -PIVATE - (cont.) A disco pre -mp (stereo) for sle, little used. Slide fders, ll tone controls. Pre -listen, pre - cueing for mgnetic crtridge turntbles. Cost 138, ccept or Mr. Wlters. Ten -chnnel stereo mixing console, printed crd construction, echo send, foldbck, cue, individul nd mster slider- fders with pds, built -in F.E.T. compressor, evox remote control unit nd mny other professionl fcilities. Two pre -wired jck fields, one dozen jck leds, pine mounting frme included. 375 csh. Genuine opportunity due to studio liquidtion, therefore no offers. Also VC53 synthesiser, s new, 300. evox pro HS77 recorder, de luxe model, self -sync 200. Two Shure 545S mies 15 ech. Phone TAPE EXCHAGES 32 -pge illustrted "Tips for Tpespondents" (Interntionl Messge Mking), I5p. Worldwide Tpetlk, 35 The Grdens, Hrrow. KEEP I TUCH WITH STUDI SUD 25p Plce regulr order with your ewsgent or tke dvntge of PST FEE Annul Subscription. IDEX T ADVETISES Acousticl Mnufcturing Ltd Hmpsted Hi Fi Acoustico Enterprises Hi -Fi ews AKG.. 626,640 Alice (Stncoil Ltd.) Leevers-ich Allotrope Ltd Apollo Electronics Mcinnes Lbs Ltd Audio Ltd Millbnk Electronics Group Audio Developments Monks, Keith Audio & Design (ecordings) Ltd Music Tpes Mil rder Audio T Audionics eumnn Avcom Systems Ltd eve & Co. Ltd., Beyer Dynmic Ltd. 628.E.W. Audio Visul Co...,. 610 ichrdson, J., Electronics Ltd Clder ec Snsui Cve, F., hi fi Shrp Electronics (UK) Ltd Frncis, J. J. (Wood Green), Ltd Frncis of Strethm Frser -Pecock Assocites Ltd ,622 Future Film Developments Ltd Sonifex Sound Equip Strmn Tpes T.B. Technicl Ltd Wlker, Grmpin Zell ecords (Birminghm) Ltd CMPETS Crbon Film. I ",,, 2"., 5'; Tol. esistors in stock. E24 rnge I 6p ech, 2% 59 ech, 5 ";, 21p ech Also in stock mny non- preferred vlues, useful for meters, etc. Metl xide esistors. 2% 1 wtt. T5. Complete rnge lwys in stock. 1 Sp ech; 100 off 34p ech. Mullrd Electrolytic Cpcitors. Complete rnge lwys in stock. Mullrd Polyester Cpcitors. Complete rnge lwys in stock. Lemco Silver Mic Cpcitors. Complete rnge lwys in stock. Polystyrene Cpcitors. Complete rnge stock. Wirewound esistors. 1W. 3W, 6W, 30W. Complete rnge lwys in stock. Semiconductors. Trnsistors, Diodes, Blocks, Thyristors, U.J.Ts., Dics, Trics, Zeners, Photocells, etc. AUDI PLUGS AD SCKETS D.I.. 2 pin L.S. Chssis. Skt.... p 2 pin L.S. Plug... 2p 3 pin 180 Plug ISp Skt 2p 5 pin 180 Plug II Skt... 5p 5 pin 240 Plug 17p Skt... Sp Jck Plugs }" Plstic 12p Screened 8p Stereo ;" Plstic 22p Screened 28p Jck Skts. Mono open I4p Mono switched p Stereo open... 20p Insulted type. 2 contct 3 contct 38p 40p lwys in 12W, 15W, ectifier F.E.Ts., P. & P. under LI p. ver LI free. MULTIPI PLUGS AD SCKETS Pinton /Jones/2/4/6/8/ 12/ 18/24/33 -wy. P.E.T. B..C. Amphenol, Cnnon, D.I.., Plessey, E.M.L. PUSH BUTT SWITCHES Multibnk Push Button Switch ssemblies now in stock. Any combintion, ltching, non -ltching, push -push, push to chnge over, push to hold, etc. J THIS LIST EPESETS A FACTI F U CMPET AGE. C. T. ELECTICS 2p. C/o 20p per button 1 P.& P. 10p 4p. C/o 30p per button }per bnk 6p. C/o 40p per button J Buttons vilble white, grey, blck, silver, red. STUDI MIT LUDSPEAKE SYSTEM E.M.I. 5 speker system. Complete with 3 -wy Vrible Crossover etwork. I only E55 TASFMES Mins Trnsformer. Pri V. Sec V. 75mA. 6.3V. 3.5A. El 75 ech. P. & P. 30p Prmeko E.H.T. Trnsformer. Type P.66890A. Pri - 240V IA. Sec. 10kV. C.T. 20mA. Enclosed in metl cse. 5" x 41" x 41 ". Weight Illb. L4.50 ech. P. & P. 75p. D. C. Tibbles & Co. Pri I V. Sec. 12V. 2 0 A ech Miniture Trnsformers. tin x 11in x Itin. Pri. 240V. Sec. 12V. ImA All types Pri. 240V. Sec. 0, 20V, 30V, ImA 65p Pri. 240V. Sec. 0, 18, 36,0, 18, mA ech Shrouded Trnsformers Pri V. Sec. 24V. 1A.... EI.25 ech Pri V. Sec. 26V. IA El.60 ech C -Core Trnsformers. Pri. 240V. Sec. 0, 71, 15V. IA El20ech... Cl 00 ech ELAYS Heter Trnsformers. Pri. 0 -I V. Sec. 6.3V. 3A Siemens Vrley Plug -in. Complete with trnsprent dust cover. 4p c/o 15,000Sì,; 5,8005 ; 2,500Sì,; 7005,; 240 Si. 50p ech. P.P. 5p. 2p c/o 700Q; 4305; 2305; 52Q; 35p ech P.P. 5p. C.P. Clre Ministure Seled 2p c/o IISL; 675.Q ; 9,100x, 70p ech. P.P. 5p. S.T.C. Seled relys 2p c/o 2,5000,; 7005;1705?,; 455t 60p ech. P.P. 5p. G.P.. elys 2p c/o H.D. 2,0005 ; 4,00051; 6,000Q 50p ech. P.P. 8p. 4p on -off H.D ,; 2,00012; 6,00052, Sp ech. 2p on -off 20,000Q 40p ech. Ltching elys. B & Type H02/T.498 2p p ech. SLEIDS 12V DC pertion 24" x 2;' di. 50p ech. P.P. Ip. ILLUMIATED PUSH- BUTT SWITCHES 2p c /o. on -locking only 35p ech. P.P. 5p. WIE -WUD PTETIMETES Colvern, elince. All vlues from I,S2,- 100KS1 19p ech. P.P. Sp. 360 wire -wound pots. Colvern. CL/6605/418 10K/í El.50 ech CL/6605/18 100KSL El.50 ech 10 -turn pots. Bourns. I KS? 5% Lin. 0.25`% E Precision Servo Potentiometers. Either %. 3" di. }" spindle, 1" spindle. L4.00 EDGE CECTS SUITABLE F VEBAD ETC 0.1" pitch 0.15" pitch 24 wy 32p 8 wy 20p 36 wy 42p 16 wy 24p P.P. Sp. 24 wy 32p VE BAD 1" pitch 15" pitch CPPE STIP 21^ x 3;" 25p 17p 21" x 5" 30p 30p 31" x 5" 35p 33p 31" x 31" 30p 30p 17" x 21" 82p 70p PLAI DILLED 17" x 31" 97p 8Sp 21"x31"I5p 21" x 5" 18p 17" x 2h" 50p 17" x 3e" 72p 17" x 5" 85p J P.P. 8p. P.P. 8p. c/o P.P. 8p. ech type e. PITED CICUIT EDGE CECTS 15 -wy Electro- Methods Ltd. KKM pitch. 40p ech. P.P. 5p. 6 -wy, 0.125" pitch. KKM.65 20p ech. P.P. Sp. WE HAVE HUDEDS F BAGAI ITEMS F THE PESAL CALLE. C. T. ELECTICS 267 ACT LAE, LD, W erest Underground- Chiswick Prk (District Line): Acton Town (Piccdilly Line). Bus outes: 53, 88, 207, 15, 7, 260. Plese ote: As not yet we do hve ctlogue vilble. Any queries plese phone or cll t the bove ddress. Business Hours: MDAY to SATUDAY 9.30.m. to 6 WEDESDAY p.m m. to I p.m. WATED SUPLUS EDUDAT CMPETS AD TEST EQUIPMET P.P. Sp 655

52 ndeh to Volume 13 A Abbey od (Visit to EMI Studios) Acoustic eserch A -3A-see reviews Acoustic wll cldding, Burgess Adhesive lbels (letter) AES Europen convention AES 40 convention report AES lecture progrmmes AES on cssettes (lecture) 367 AES -UK brnch formed 7 Agf -Gevert move AI -see Studio Directory Aki see Servicing AKG D202 -see Impressions nd eviews Aldwych thetre sound system Ampex wrded 100,000 for colour brodcsting equipment 275 Ampex cssette duplictor Ampex Instvision -nme chnge Ampex 200 mster tpe plyer Ampex videotpe duplictor Amplifier, A verstile recording (constructionl) Amplifier Power -see Servicing An IC trnsformerless microphone mplifier (constructionl) APS ppoint new secretry APS 1971 preview 300 APS 1971 report Argo ppoint gent AUD THE STUDIS Abbey od Audio Interntionl BBC Mid Vle ne 60 Commnd.. 22 Gemini Hollick & Tylor 183 Intersound Islnd Lnsdowne Mjestic Mrquee ecorded Sound Cnby, E. T. Sound minus sync.. 343, 403 Conduit, C. S. An IC trnsformerless microphone mplifier (constructionl) Dykes, I. Thetresound Emmerson, V. Video dely modules Fisher, J. H. A stereo cpcitor microphone (constructionl) , 191, 225 Building your own Microphones The quiet ccompnist Chrome.. Comprison: Studio microphones.. Dolby B320 (review).... Grundig TK 3200 (review).. ecording studio techniques , 69, 111, 177, 247, 277, 337, 391, 449, 531 Telcon Telshield (review) Understnding time constnts Weirclifte Model 8 bulk erser (review).. 87 ylor, M. Building povum (constructionl) Four chnnels on budget Sundy sound obinson, D. A high qulity mixer (constructionl) 19, 77, 122, 166, 234 Workshop objohns, E. Why so mny tpe recording stndrds? 83, 109 Ford, H. Level) TG200 CM oscilltor (review) Miniflux ME 104 & ME 301 (review) Grrtt, A. A CCI to DI Adpter (constructionl) Gerzon, M. Experimentl Tetrhedrl ecording 396, 472, 510 Synthetic stereo reverbertion Why Coincident Microphones? Golding,. The Tndberg Lnguge Lbortory Hywrd, L. The 'Virtul Erth' s Mixer Self, P. Comprison: Microphone stnds Shuttleworth, J. Acoustic eserch A -3A (review) AKG D202 (review) Impressions , 65, 243 Inside Mid Vle (Around the Studios).. 60 Kellr KDB1 (review) Keith Monks Stnds eview gr 4D (review) Tht ws APS Skeet, M. G. 279 The Invisible Switch Hellyer, H. W. Tutchings, A. Servicing 26, 62, 162, 231, 306, 354, 405, 466, 536 Amplivox Astrolite (review) B & stereo ribbon microphone (review).. 36 Hill, P. J. & Howe, B. A Cssette /Slide Synchroniser (constructionl).... Hope, A. AP for hire Mobile Stones A -3A review (letter) Music off the Streets Audio nd coustic Mesurements (orth Ptents eview.. 316, 368, 416, 465, 539 London Polytechnic lectures) 498 Studio Who 533 Audio nd video rentls Audio Annul Kirk, D. Audio Interntionl -see Around the Studios APS 71 preview Audio Systems -see Studio Directory Hollick & Tylor (Around the Studios) Audio Trnscriptions -see Studio Directory B & 1800 (field tril) Bell & Howell Filmosound (field tril) AUTHS Clrec 1050 cpcitor microphone (field tril) 90 Anscomb, J. H. EMS VCS3 Synthesiser (field tril) Crtoon Philips Pro 12 (field tril) Sony DVK 2400 Act (field tril) Auger,. Inside Commnd (Around the Studios) 22 Why multitrck? 85 Sound '71 report Where it goes Wlker, E. 21 ecording those mighty firground orgns 29 Wicks, K. Around the Studios: Abbey od Audio Interntionl Gemini Intersound Islnd Lnsdowne Mjestic Mrquee.. 10 ecorded Sound Studio Diry 131, 179, 219, 283, 333, 383, 441, 504, 554, 623 Tht ws APS The Wonderful Sound of dio.. 353, 409 Bstin, P. Levesley, P. Profile Designing studio mixer 346, 399, 451, 525, 581 Tlkbck.. 92, 293, 415 Bng & lufsen see field trils Loms, P. A. Brrett, Deth of W. J. H Bell, C. H. AES 40 convention (review) BASF record releses, First Creting musicl 471 Spendor stereo mplifier (review) BASF revisited BBC buy neve console Blckhm, T. G. McKenzie, A. BBC contrct, Zonl wrded Film sound technique.. 188, 238, 280, 357 BASF evisited BBC order EMS synthesiser u B

53 IDEX T VLUME 13 continued Bens, ecording jumping Beldfoil shield B & reorgnise gurntee rrngements Book reviews.. Brodcsting with Dolby B BSI publish film /tpe sync stndrd.. Budget four- chnnel Building povum (constructionl).. Building your own Bulk ersers (constructionl).. Burgess coustic wll cldding C , Clrec -see Studio Directory Clrec southern distribution Cpcitor microphone, oise cncelling Crston, London office for Crtridges t US Trde centre Cssette duplictor, Ampex Cssette nd tpe dupliction -see ecording Studio Techniques Cssette, Philips 'professionl' CBS qudrphonic disc CBS /Sony nnounce qudrphonic disc CCIC to DI dpter, A Chrome Chrome, McKenzie on (letter) Clutches -see Servicing Coxil connectors.. Coblt tpe, 3M produce Coincident microphones (letters). Coincident Microphones, Why? Commnd, Inside. Commnd Studios, Qudrphonics t Commercil rdio Comprison: Microphone stnds. Comprison: Studio microphones. Components ctlogue Connecting boxes , , , Constructing tpe cssette /slide synchroniser (constructionl) Constructing one -off equipment Creting musicl D Designing studio mixer 346, 399, 451, 525, 581 Desoldering n IC Detchble cpcitor cpsules (letter) DI Adpter, A CCI to Disc, CBS /Sony nnounce qudrphonic Disc processing nd pressing -see ecording Studio Techniques Dolby B brodcsting Dolby B ferrogrph Dolby B IC Dolby B (letter) Dolby B320-see eviews Dubreq introduce PinoMte Dupliction, Mss cssette nd 593 E Editing -see ecording Studio Techniques Eel Pie Instl eve EMI L4 bttery power unit.. EMI Studios (visit to Abbey od) Europen AES convention.. EV developments Exhibition, VT.. Experimentl tetrhedrl recording F Fder, Argo low cost.. Feldon, Wht hppens t?.. Ferrogrph udio test unit.. Ferrogrph Seven -see Servicing , 472, Ferrogrph with Dolby B Festivl du Son.. FIELD TIALS Bng & lufsen 1800 Bell & Howell Filmosound.. Clrec 1050 cpcitor microphone.. EMS VCS3 Synthesiser.. Philips Pro Sony DVK 2400 ACE bttery VT Loction, ecording on -see ecording Studio 215 techniques London office for Crston Loudspekers (letter) Loudspekers, Survey of monitor Low -cost illuminted switches Low -price L Film preview thetre, Scotlnd's first Film sound technique , 238, 280, 357 Film tpe sync stndrd -BSI Filters nd equlisers (High qulity mixer).. Fine rt of voltge control, The First BASF record releses.... Flexible LP discs Four chnnels on budget.. Frnz, Wilhelm (obitury) French sound festivl.... G Geesin unlimited, on Gemini, Inside.. Gropius on wire (letter) H Hedphones (letter) 187 HH telephone chnge High qulity mixer, A (constructionl) 19, 77, 122, 166, 234 High qulity mixer prts Hollick & Tylor -see Around the Studios I IBC cll for ppers IC udio mplifier.. IC Dolby B.. Illuminted switches, Low cost.. IMPESSIS As good s cpcitor? (AKG D202) Ever been conned.. Setting up.... Industril equipment retiler Inside Commnd.... Inside Gemini Inside Intersound Inside Mid Vle Inside Islnd Instvision -nme chnge Invisible switch, The.. J Jones Electronics Ltd, ew nme for Jumping bens, ecording.. K Kellr KDB1 -see eviews Kellr KDB1 (letter) L Lnguge lbortory, Tndberg Lnsdowne Studios -see Around the Studios Leevers -ich cquired by MCP Leevers -ich ppointments Leevers -ich eight trck instlled t Hrlech TV Leevers -ich lnguge lbortory Leevers -ich, 25,000 order for Letters ,187 Levell TG200CM -see eviews Limiters nd Compressors (High qulity mixer) 122 Limiting, Compression nd expnsion -see ecording studio techniques 657 M Mjestic -see Around the Studios Mking it stick (letter) Mrquee -see Around the Studios McKenzie on chrome (letter) MCP, Leevers -ich cquired by Microphones Microphone Survey Millbnk move south Miniflux ME 104 -see eviews Miniflux ME 301 -see eviews Miniflux qudrphonic tpe reply mplifier Minimoog introduced Mixer, Designing studio 346, 399, 451, 525, 581 Mixer, High qulity 19, 77, 122, 166, 234 Mobile Stones Monitor loudspekers -see ecording studio techniques Monitor loudspekers surveyed 222 Moog introduces his Mini Mosely on qudrphonics, John 109 Multitrck, South cost.. 59 Multitrck, Why? Multitrcking to sve time (letter) Music off the streets Musicl, Creting Muzk dupliction equipment, Pye supply.. 59 AB 203 reels, Scotch mrketing gr 4D -see eviews tionl produce miniture CCTV.. eve console for BBC.. evin printed circuits.... oise -cncelling cpcitor microphone oise mesurement techniques (Dwe Booklet) ottinghm, Studio opens in bitury: Wilhelm Frnz P Pn Ptents eview.. 316, 368, 416, 465, 539, 591, 616 Pek oriented VU Meter, Building (constructionl) Performing ight Society grnts Phse indictor, A stereo Philips EL Philips EL see Service 27 Philips noise suppression unit Philips 'professionl' cssette PinoMte, Dubreq introduce Pie instl eve, Eel Plug -in Audio modules Polycourses Post office lines (letter) Printed circuits, evin 'Professionl' Sony Profile Pulse counters, ITT Purchse tx chrges Pye supply Muzk dupliction equipment.. 59 Qudrphonics t Commnd Studios 215 Qudrphonic disc, Sony /CBS nnounce Qudrphonic tpe reply mplifiers (Mini- flux)

54 IDEX T VLUME 13 Setting up -see Impressions SS lunch PA equipment continued Sonex ' Song fodder (letter) Sonifex portble mixer Sony/CBS nnounce qudrphonic disc Sony develop low -cost colour TV cmer dio, The wonderful sound of.. 353, 409 Sony DVK24000 ACE bttery VT -see Field Trils CA develop cmer tube with memory.. 7 Sony introduce AB spool recorder 459 CA win 3,000,000 studio order.. 59 Sony 3664 four -chnnel-see eviews ecorded Sound -see Around the Studios Sound minus sync ,403 ecording mplifier, A verstile Sound '71 preprtions ecording on loction -see ecording Studio Sound '71 (APAE exhibition report) Techniques South cost multitrck.. 59 ECDIG STUDI TECHIQUES Disc processing nd pressing.. Limiting, Compression nd Expnsion Mss cssette nd tpe dupliction Monitor loudspekers Qudrphonics.. ecording on loction.. Session mngement nd editing Stndrd levels.. Stereo microphone technique Test equipment Test tpes in servicing ecording those mighty firground orgns.. 29 eport on the AES 40 convention EVIEWS Amplifiers Spendor S 209 stereo.. Audio Processors Dolby B320 Kellr KDB1 Books Loudspekers Acoustic eserch A -3A.. Microphones AKG D202 Miscellneous Telcon Telsheld.. Keith Monks Microphone Stnds.. Tpe ecorders gr 4D.. Sony 3664 Test Equipment Levell TG200CM udio oscilltor.... Miniflux ME 104 wow nd Flutter meter.. Miniflux ME 301 wve nlyser.... EW to retil industril udio equipment obinson mixer prts.. on Geesin unlimited.. S Sfegurding PA equipment.. Sit mrket mixers Scotch mrketing AB 203 reels.. Scotlnd's first film preview thetre.. SEVICIG Amplifier power Brkes.. Clutches.... Ferrogrph Seven Tpe speed control 249 Speed control -see Servicing Stereo cpcitor microphone, A (constructionl) , 191 Stereo cpcitor microphone, Constructing A 225 Stereo Fi -Cord (letter) Stereo microphone technique -see ecording Studio Techniques Stereo phse indictor, A Stones' mobile studio Studio diry 131, 219, 283, 333, 383, 504, 554, 623 STUDI DIECTY Air Audio Systems Audio Trnscriptions.. Clrec Centrl Scotlnd Centrl Sound.. Grhm Clrk.. Commnd Studio equipment sles Studio mixer, Designing 346, 399, 451, 525, 581 Studio opens in ottinghm.... Studio order, CA Win 3,000,000 Studio Who Sundy sound (Yorkshire TV) Survey of monitor loudspekers.. 181, 241 Switches, Low -cost illuminted.. Synthesiser, BBC order EMS.. Synthetic Stereo everbertion Systeme Interntionle T Tlkbck , 92, 165, 415 Tlkbck nd dimming switches Tndberg lnguge lbortory Tpe cssette /slide synchroniser, constructing Tpe dupliction, Mss Cssette nd -see 311 ecording Studio Techniques 595 TAPE ECDE SEVICE Aki Philips EL Philips EL Uher 4000L Uher4200L , Tpe Speed Control -see Servicing 577 Terry clips (on microphone stnds) Test tpes in servicing -see ecording Studio Techniques Tetrhedrl recording, Experimentl 396, 472, 510 Tht ws APS Thetresound The quiet ccompnist Thorn to produce videocssette equipment M produce coblt tpe Trnsformerless microphone mplifier, An IC Turntble -see Letters , TV cmer, Sony develop low -cost colour U Uher 4000L nd 4200L -see Servicing Unuthorised lbum.... Understnding time constnts.. v Veg 800 recorders Verstile recording mplifier, A.... Videocssette equipment, Thorn to produce Videocssettes, Ampex.. Videocssettes, Philips Video consortium, W. H. Smiths loin.. Video dely modules.. Video tpe duplictor from Ampex Video tpe recorders, Survey of Virtul erth s mixer, The.... Visul monitoring (letter).. VT exhibition.. W Wht hppens t Feldon?.. Where it goes (microphone plcement) Who, Studio Why coincident microphones? Why multitrck? Wonderful Sound of dio, The Workshop.... Z Zonl Awrded BBC Contrct Zonl Introduce Spectrum tpe PAGE SEQUECE Jnury Februry Mrch April My June July August September ctober ovember December 1 to to to to to to to to to to to to , PAST ISSUES A smll number of certin pst issues my still be purchsed from Link House, price 31p ech including postge. 159 Photostt copies of ny STUDI SUD rticle 286 re vilble t 25p including postge. Published by the Proprietors, Link House Publictions Limited, South Crescent, Store Street, London \V C.I, nd Printed by Arthurs Press Limited, \\bodchester, Stroud, Glos. GL5 5P3.

55 122/ 124 BIG MEY SAVIG CATALGUE Send9p AD 2000 (C) Armstrong Cmbridge P ogers /bourne (C)... E49.25 ogers /brook (C) otel A3I otel A6I E5525 Sinclir 2000 Mk Sinclir Sinclir eoteric Snsui AU I Snsui AU E52-95 Snsui AU555A Snsui AU E92.95 Snsui A E44.90 Lux SQ E84 50 Lux SQ Lux 5077T Lux SQ Grundig SV El Grundig SV Metrosound ST2E Qud Philips H Pioneer SA EI10-50 Pioneer S Ferrogrph F307 Wood C E48 95 Ferrogrph F307 Metl C E46.95 Teleton SAQ E18.50 Teleton GA E25-00 Peksound Englefield E38 95 Peksound Englefeld 870A Armstrd TUES P & C Armstrong Armstrong 524 E33 75 Armstrong M8... E8 25 Decc ogers /brook (C) f41 95 otel STI20 E38 95 ote' T Snsui TU EE 45 Snsui TU E70 95 Lux WL E79 95 Grundig TI00... E Philips H E41 35 Teleton GTI01 E35 95 i TUE AMPLIFIES P & C L1.25 Aki AA Aki AA E Aki AA Armstrong 525 E74.50 Armstrong otel FAX660A 8590 otel E5750 Snsu Snsui Whrfedle 100-I... E92-50 Tndberg Hi-Fi FM (Tek)... L63.90 Tndberg Hi-Fi FM (osewood)... 66S0 Tndberg SSI171 (Tek) E83.25 Grundig TV Grundig TV650 E Pioneer LX E9550 Pioneer KX E68-95 Teleton C10T... f19.95 Telecon CIT with two Teleton SA125 spkrs. E2585 Teleton T Teleton F E2950 Teleton TFSSLA... f61.50 SPEAKES P & C LI 75 A6Tk A4XTk B & W DMI 3350 Celestion Dicton E31-95 Celestion Dicton Celestion Dicton G /mns Mezzo G Imns Mezzo G /mns Mgnum K G /mns Mgister Kef Celeste... E25-50 Kef Cdenz... 05'95 Kef Concerto Mk ichmond E19.95 ichmond E22.95 ichmond Mk Philips L561 / Philips H Lek Mini Tek... E23.50 Lek Mini Wlnut Lek Sndwich Lek Sndwich 200 E19.95 Lowther PM Qud Electrosttic Dyntron LSI Dyntron LS2034T Keletron K Keletron K Keletron KI Grundig L67.25 JBL Tnnoy LLILZ Tnnoy 15" Lnc. L58.65 Cmbridge 50 E83.50 Cmbridge 40 E56.95 W /Dle Denton Pr E26-95 W /Dle Triton Pr W /Dle Melton 2 L28.00 Keith Monks Elf E15.50 STE MA E26.95 HEADSETS P & C 25p F. CAVE Aki ASE9... L5.20 Beyer DT48S... L28.95 Beyer DT EII.85 Beyer DT Koss ed Devil Koss SP3X0 Koss K Koss P4AA Koss ESP6... Koss ESP9... Pioneer SES... LIS85 Pioneer SE Pioneer SE20... E6.20 Pioneer SE2P L5.60 otel H7I I... L8.25 Snsui SS Snsui SS20... EI5-00 Secom L2.95 TUTABLES P & C McDonld M P60... L11-95 McDonld MP60 /W/P - I McDonld 610 /W /P & C McDonld 310 /W /P & C B & C for McDonld Tk B & C for McDonld Dul Dul Dul 1219 /M9IMGD Trnscriptor /Arm/Cover Trnscriptor 9" or 10" Arm Grrrd Grrrd SL5B Grrrd AP Grrrd SP25 Mk I I -25 Grrrd Grrrd40B Grrrd SL65B Armstrd B & C for AP Armstrd B & C for SP Connoisseur BD2 /P /PC /Arm Connoisseur BDI Kit Goldring Goldring GL69 P & C Goldring GL Goldring GL75 /P & C Goldring GL75 /P & C/G800E Philips GA Thorens TD Thorens TD 150AB... E41 I S Thorens TXI Pioneer PI 12A IS Howlnd West HWI Howlnd West HWI SME CATIDGES P & C 17p AT66LC L5-00 Empire 1000 ZE Empire 999 VE... E TEX... L S /EX EI F/EX... E13.25 Empire 808E L10.25 Empire G /ring G800 Super E... E17 75 Gering G800E... E1I95 G ring G L7.75 Glring G E4-50 Gering GS 91 E... L6.25 Sonotone 9 Dimond Connoisseur SCUI... L5.20 Decc S /Blue Decc E /Gold E5.00 Shure VIS... t30-95 Shure M 75E. fi5.50 Shure M Shure M 55E L10.50 Shure M 44E E9.50 Shure M 44-5 E8.25 Shure M E8.25 Shure M 91E Shure M 92E L16-50 Shure M 93E E TAPE ECDES P& CE175 Ferrogrph 702/ Ferrogrph 722/ /704 HS /724 HS Tndberg 1541 Tk... E79.20 Tndberg 1541 osewood Tndberg 1221/1241X Tndberg 64X E Tnd berg 3041X Tndberg 4041 X Tndberg E62-60 Tndberg E59S Grundig C-200SL E31.50 Grundig TKI21 E47.50 Grundig TK141 E51.25 Grundig TK Grundig TK E GrundigTKl24... E31.00 Grundig TK E33-50 Grundig TK S Aki 4000D L6750 Aki 1720L Aki Aki X5000L E14500 Aki M-10L E Aki X-2000SD... E Aki E11595 evox 1102/ Prices evox 1222/ on evox 1 1 Appliction Philips E43.50 Philips Philips E80.25 Philips E92.95 Philips Telefunken M Telefunken CASSETTE ECDES P& CLI-25 Philips Philips Pye Corondo... L33-50 Teleton HSI00... LI5.95 MICPHES P & C 35p Beyer M E22.25 Beyer M E2350 Beyer M260SM I I Beyer XI E19 50 Beyer MSIHL Beyer MS18HL E2450 Beyer M55HL Egle DM16HL E5.75 A.K.G D119ES A.K.G. D202SS ADI GAMS A.K.G.D19C/ E1840 Decc Decclin TndbergTM E10'95 Decc Decclin Philips E3 50 Philips GE L42.70 Philips Philips GE L84.95 Clrex CM Clrec CM E27.50 Clrec CM E27.95 AUDI SYSTEMS Clrec CM Decc 603 E53-75 PICKUP AMS P & C 35p Clrec CM Decc Connoisseur SAU2 E12.25 Decc G /ring L SPEAKE UITS Decc L85-70 G /ring L Tnnoy I LZ... L26.35 Decc I2150 Trnscriptor 9 "/I0" Tnnoy 12' Mrconiphone 3... L74-40 SME L27.70 Tnnoy 15" E36.75 Mrconiphone AT 1005 EI6-85 W /dle 3 f108s Teleton 2360F L59-95 All Prices Subject To Altertion Without otice E. &.E. 4 W /dle 4... E W /dle 5 E21 45 G /mns Axiom 201 G'mns Axiom 301 Glmns Axiom 401 Kef Speker Units Prices on Appliction 8 TACK STEE Aki C Aki C8D... E69.80 Pioneer TP Motorol/cr Metrosound 448. E47.35 Metrosound Mk Ill E40-95 Metrosound SS Tel econ STP800 E41-95 ADIS P & C 75p Grundig Solo Boy Grundig Prty Boy Grundig Music Boy Grundig Elite Boy Grundig Ycht Boy 3250 Grundig FIII Tndberg TP 41 W Zenith TAPE P & C eels 7p Cssettes 3p BASF LW ISE HIGH UTPUT 51" 1200'... L I 30 7" 1800'... LI 85 51" 1800' L 85 7 "2400' L "2400' E2 26 7" 3600' E2 82 BASF, PHILIPS & SCTCH DYAAGE CASSETTES C30 L 45 C C C SCTCH DYAAGE 7" 1200'... LI.42 51" 1200'... E1.40 7" I800' ;"2400'... E2-73 5" 1200' E1.56 5g"1800' LI.81 7" 2400' Top Discounts Hi Fi & Audio WEST ED 21 LD CMPT ST. W.1. ICHMD SY. 5 BIDGE ST KIGST SY. 27 EDE ST mil orders 5 HE CT. ICHMD SY. Suppliers of Hi Fi Equipment, Audio nd Electricl Goods from the World's Top Mnufcturers PESAL EXPT EASY CEDIT TEMS EPAIS FULL MAKES GUAATEES

56 ev SUD CTL CSLES S.16-4 Illustrted below - BCM 10-2 S.24-8 Section of wiring shop t the Melbourn fctory The 'S' nge for rpid delivery Built into every model in the 'S' rnge is the ccumulted experience nd technicl knowledge gined from mny yers of designing nd building sound control systems for leding recording, film, b odcsting nd television sttions throughout the world. The result istht the customer cn now order virtully "off the shelf ". It lso mens considerble svings in money nd time. Consoles incorport most of the dvnced fetures built into eve consultnt designed equipment. Every console is built to the identicl stndrds tht chrcterise ll eve products. The rnge comprises three models plus series of portble sound mixers. Full detils of these consoles will be sent on request. Enquiries lso invited for Consultnt Designed Consoles to customer's specil requirements. SC/ input chnnels. 2 /P groups. 1 reverb. group with stereo return. Meters, tlk bck, Cue /PFL speker, etc. S input chnnels with full equlistion. 4 /P groups. 2 reverb. 2 foldbck, 8 trck plybck. 5 V.U. meters. 4 limiter /compressors, etc. S input chnnels, 8 /P groups, 13 meters, filters. 16 trck reduction monitoring, etc. The Sound of eve is Worldwide upert eve & Compny Ltd. Cmbridge House, Me!bourn, oyston, Herts, SG8 6AU, Eng'nd. Telephone: Melbourn (Cmbs) 776 (STD ) 10 lines Telex upert eve Inc. Berkshire Industril Prk, Bethel Connecticut 06801, U.S.A. Telephone: (203) Telex upert eve of Cnd Ltd. P.. Box 182, Etobicoke, ntrio, Cnd.'Telephone : (416)