Both sides of the Atlantic Ocean can

Transcription

1 on test kef reference 3 loudspeakers Both sides of the Atlantic Ocean can make genuine claims to producing icons in loudspeaker design. Our American friends JBL and Klipsch come to mind straight off, while across the pond Tannoy would be first name off many-anenthusiast s lips. Of course, another emblem of British speaker aristocracy would have to be the company whose full name is Kent Engineering & Foundry but is more commonly known as KEF. KEF was started in 1961 by engineer Raymond Cooke who, after spending influential years working alongside Wharfedale founder Gilbert Briggs, decided to go it alone. In the years since KEF s inception, and on to the present day, several things have remained constants. Primarily, the substantial R&D and thoroughly-engineered designs some industry firsts among these followed by in-house driver development and consistent product quality backed by intelligent marketing. Over the years, all those aspects have secured a global base of loyal KEF customers. And lastly, since the 19s, the enduring Reference series until the recent advent of Muon, the Blade concepts and the odd commemorative model such as the Maidstone has represented the company s flagship offering. Now, in 2015, KEF has announced a new Reference product line that benefits from the latest implementation of the company s proprietary Uni-Q coincident driver technology, which has been in continuous refinement since the 19s. 54

2 KEF Reference 3 Loudspeakers on test The new Reference products include a large standmount, two floorstanders, two centrechannels and a subwoofer. Here we review the KEF Reference 3 which may be the smaller of the two floorstanders but is by no means a small speaker. It stands metres high, is 4mm deep and 349mm wide. It weighs in at 51kg so substantial by any standard. The Equipment The Reference 3s are delivered well-packed in high-grade cardboard boxes with the speakers themselves wrapped in a protective white cotton sleeve. The shapely solid metal plinths, which require assembly to the speakers bottom panel via short hex-head bolts, feature welded cones which serve as receptacles for nicely-machined stainless steel spikes. Two very convenient touches: the plinths feature an integral spirit level and a system for conveniently adjusting the spikes penetration and levelling from above, via machined and anodised aluminium turning discs. Metal floor protectors are also provided. The accessories are attractively presented in a box with individual foam cut-out receptacles for the various pieces of hardware. KEF provides two sets of port inserts allowing basic matching to room bass characteristics (more on this later). No grilles are included; why would you want to tarnish the gorgeous aesthetic with a black cloth? The KEF Reference 3s baffles are gloriously finished in brushed aluminium and should be displayed for all to see. In fact, the entire presentation is first class with the review sample clad in the extra cost and absolutely stunning pair-matched gloss rosewood finish, which retails for $26,599. (Special Kent Engineering and Foundry Editions are also available in gloss white with Blue Ice Uni-Q driver colour and gloss black with Copper -coloured Uni-Q drivers). The standard cabinet finishes, which I was able to examine at the recent official Australian launch, were equally spectacular. So, whether you fork out for the optional finishes or decide on one of the standard finishes, you ll own a beautifully-designed and finished pair of loudspeakers. The Reference 3 (Ref 3 from now on) is a three-way twin-rear-ported design featuring the latest Uni-Q point source driver array, versions of which have been the trademark KEF mid/high-frequency solution for many generations. The Uni-Q driver features a 25mm vented aluminium dome with the Tangerine wave guide mechanism used coincidentally within the acoustic centre of a 125mm aluminiumconed midrange driver. Bass duties are provided via twin 1mm aluminium-coned woofers featuring massive vented magnet systems and high-temperature aluminium wire voice-coils for high power-handling. As per tradition, all the drivers are built in-house by KEF and are representative of No grilles are included; why would you want to tarnish the gorgeous aesthetic with a black cloth? the best available technology on a par with the highest-level products from the leading specialist transducer manufacturers. The crossover points are specified as 3Hz and 2.8kHz, while the crossover itself features high-quality components. The drivers are flawlessly mounted no ugly screws or bolts showing in a thick aluminium and resin sandwich baffle that is decoupled from the enclosure via high-loss pads. KEF specifies a frequency response from 43Hz to 35kHz ±3dB but says the speaker can deliver frequencies as low as 28Hz in a typical in-room situation. Sensitivity is quoted as being 87.5 while the nominal impedance is quoted as being 8Ω with a 3.3Ω minimum. The basic instruction manual includes a separate production certificate which guarantees Reference series speakers are quality inspected individually and pair-tested to ensure the frequency responses of the two speakers match within a tolerance of 0.5dB. The certificate also features a frequency response graph and the assurance that the speakers have been hand-built and tested by a master technician in the case of the review pair it was a Graham Humphries of Maidstone, Kent. The Ref 3 enclosures feel substantial. Care has been taken to produce a constrained-layer-damped cabinet that is stiff, well-braced, and which should provide a platform for the high-tech drivers to perform at their best. Once unpacked, all that is required is the attachment of the metal base, then the speakers can be positioned and levelled. I also liked the superb easy-to-tighten custom binding posts and the simple twist arrangement for switching between single- and bi-wired configurations. Ports of Call As mentioned previously, KEF includes a choice of soft foam slide-in/slide-out port inserts (first seen in the much-lauded LS monitor) which provide different lowfrequency roll-off characteristics for basic bass tuning. A simple twist-to-lock/unlock ring provides access to either a short ivorycoloured foam port insert (for use when the speakers are positioned away from walls) or a longer black-coloured port (for nearsolid-wall placement). My own listening room is remarkably neutral and features an acoustically near-invisible rear wall so I chose the short port inserts. Kudos to KEF for providing some form of tuning system, rudimentary though it may be. Ergo the Ref 3 s lower frequencies, both in terms of power and depth, were quite spectacular considering the modestly-sized twin bass drivers. There was power, punch and speed akin to sealed box/infinite baffle designs. You know, that bounce that defined leading edge that, once heard, you become addicted to. And the quoted in-room response of 28Hz is not at all farfetched; the Ref 3s dip low and with um, ample amplitude. My usual suspects in the bass-testing department provided a thrilling ride into realistic bass and power from a relatively compact floorstanding speaker. Acoustic bass, in particular, sounded tonally correct and with an accurate balance of bloom and solidity while electric bass had the kind of speed (or bop) that propelled

3 on test KEF Reference 3 Loudspeakers the music along, maintaining its rhythmic integrity. These woofers may be relatively small but they re powerful, high-output, lowdistortion drivers. At the other end of the scale, the Uni-Q drivers high frequencies are a model of refinement and subtlety. Some audiophiles may prefer a more overt, more forward treble, but this reviewer (in the context of the reference system) found the high frequencies were spectacularly delicate, natural and rich in timbral textures. The KEF tweeter implementation, with all its design and physical placement complexities, is nevertheless a rather beautiful driver that integrates seamlessly with its midrange partner, itself a stunning performer with all-manner of vocals, be they male or female. The Ref 3 speakers are a succinct example of the modern speaker designers art... To some music-lovers, soundstaging is of the utmost importance while others value dynamic expression and tonal accuracy above all else. All, of course, are important. Having said that, the Ref 3s threw one of the widest and deepest soundstages I have experienced in my room and did not require a head-in-a-vice sweet spot position to achieve this. Classical and jazz recordings the ones captured live either in the studio or at a hall/club such as Harry Belafonte s Live at Carnegie Hall, or Ani DiFranco s Living in Clip were reproduced with extraordinary largesse, in all dimensions, in a panoramic soundfield. Images were precisely placed in a sonic environment of exceptional width and revelatory depth way, way beyond the front wall. Combine that with another of the Ref 3s strengths, that of significant dynamic prowess, and you have a speaker that gets you closer to the music real music. Yes, the KEF Ref 3s scale the dynamic paradigm to an enormous extent. Once again, I d accredit that to the superb drivers, solid enclosure and transparent crossover working in unison allowing the transmission of maximum information from the given input signal. Those same aspects I would pass on for the reasons behind the merciless separation and detail retrieval. I use the word merciless in a most positive way too; these speakers are true to the source they will not taint with syrupand-molasses nor will they detract from the absolute and potentially revelatory truth. If the recording is romantically warm, or conversely, frightfully compressed, given neutral electronics, the Ref 3s will be the faithful relater of the undistorted message. And that is exactly as it should be. Conclusion KEF s Reference 3s were amongst the most satisfying speakers I ve had the pleasure of reviewing for quite some time. Within the context of my reference system, they shone as truly outstanding transducers, excelling in some of the most important aspects of music reproduction such as dynamic extension, bass power, soundfield reproduction and tonal accuracy. The Ref 3 speakers are a succinct example of the modern speaker designers art. Here is a statement reflecting the power of thorough engineering encompassing all facets of loudspeaker design; from the in-house built drivers, to the solidly constructed enclosure and transparent crossover and on to the acceptability, and indeed pride, of the product in the home via its attractive form and flawless finish. Ever still, KEF the company is a foundry for exceptional engineering. Edgar Kramer KEF Reference 3 Loudspeakers Brand: KEF Model: Reference 3 Category: Floorstanding Loudspeakers RRP: $23,999 (See Copy) Warranty: Five Years Distributor: Advance Audio Australia Address: Unit 8, Parramatta Rd Leichhardt NSW 20 T: (02) E: info@advanceaudio.com.au W: Huge sound belies the physical size Thoroughly engineered Beautifully styled and finished The temptations of the Reference 5? LAB REPORT: Turn to page 57 Test results apply to review sample only. 56

4 KEF Reference 3 Loudspeakers test report Laboratory Test Results measured the frequency response of the KEF Reference 3 speakers as extending from 34Hz to 35kHz ±3dB: a truly excellent result that betters KEF s own specification. Even more importantly, the response was almost perfectly balanced, so that the demonstrably small variations in the response were spread across the audio spectrum, rather than there being an emphasis in a particular frequency region. The response across the all-important midrange was spectacularly good, so that from Hz up to 5kHz it barely varies more than ±1dB. All this is shown in Graph 1, in which the trace derived from an averaged in-room pink noise measurement (the trace below 1.5kHz) has been spliced to a gated (anechoic) high-frequency measurement. The slight trough in the response centred at 1Hz is the point at which the bass drivers cross to the midrange driver so has been slightly affected by microphone positioning. The output is actually a little flatter across 20 Hz K 2K 5K 10K 20K K Graph 1. Frequency response. Trace below 1.5 khz is the averaged result of nine individual frequency sweeps measured at three metres, with the central grid point on-axis with the tweeter using pink noise test stimulus with capture unsmoothed. This has been manually spliced (at 1.5kHz) to the gated highfrequency response, an expanded view of which is shown in Graph 2. [KEF 3] 0 Hz 0 1K 2K 5K 10K 20K K Graph 2. High-frequency response, expanded view. Test stimulus gated sine. Microphone placed at three metres on-axis with dome tweeter. Lower measurement limit 0Hz. [KEF Reference 3 Loudspeaker] 30 Ohm Deg Hz K Graph 3. Low frequency response of lower bass reflex port (green trace); upper bass reflex port (red trace); woofer (black trace) and midrange driver (blue trace). Nearfield acquisition. Levels not compensated for differences in radiating areas Hz K 2K 5K 10K 20K K Graph 4. Impedance modulus with black bungs (pink trace) and white bungs (brown trace), plus high-pass section (green trace), low-pass (blue trace) and phase (black dotted trace). Solid black trace under is reference 3 ohm precision calibration resistor. [KEF Reference 3 Loudspeaker] 20 Hz K 2K 5K 10K Graph 5. Averaged frequency response using pink noise test stimulus with capture unsmoothed. Averaged result of nine individual frequency sweeps measured at three metres, with the central grid point on-axis with the tweeter. 20 Hz K 2K 5K 10K 20K K Graph 6. Composite response plot. Red trace is output of lower bass reflex port. Green trace is anechoic response of bass driver. Light blue trace is sine response of midrange driver. Pink trace is gated (simulated anechoic) response above 1.5kHz spliced to third-octave smoothed version averaged in-room pink noise response. [KEF Reference 3] 57

5 test report KEF Reference 3 Loudspeakers this region, as demonstrated in Graph 6, which shows the relative outputs of the bass drivers (green trace) and the midrange driver (light blue trace). The anechoic frequency response of the KEF Reference 3, as measured by Newport Test Labs, is shown in Graph 2 in expanded form, enabling finer details to be shown in the response. You can see that the response rolls off above 9kHz to 16kHz, after which it plateaux then extends out to around 28kHz followed by a further slight roll-off and then a rise to the tweeter s resonance at 39kHz. Once again, you must admire the linearity of the frequency response below 5kHz, where it virtually tracks the horizontal graph line down to the lower graphing limit (0Hz). This is truly exceptional performance. Low-frequency performance is shown in Graph 3. The output of the two rear-firing bass reflex ports (measured using the longer, black port inserts, rather that the shorter ivory ones) was slightly different, due to them being spaced apart by 44cm. You can see the upper port has a slightly peakier, higher-q output, which peaks just below Hz, while the lower port s output has a lower Q and peaks just above Hz. There s no high-frequency leakage through the ports at all, which shows great design work on KEF s part. The bass driver s output minima is a little higher than the peak port outputs, at Hz, showing KEF s engineers have tweaked the design to give a little more deep bass. The midrange section of the coaxial driver rolls on at around 6dB per octave, for an apparent acoustic crossover at around 1Hz, (KEF specs the electrical crossover at 3Hz) where its output takes over from that of the bass drivers. It then continues within around ±1dB up to the 1kHz graphing limit. KEF rates the nominal impedance of the Reference 3 design at 8Ω with a minimum impedance of 3.2Ω, and this is exactly what A great example of an outstandingly well-designed loudspeaker that has an incredible flat and linear response... was measured by and is shown in Graph 4. You can see that the minimum 3.2Ω impedance occurs at two frequencies: 54Hz and 130Hz. The lowfrequency resonant peaks are lower in level than I am used to seeing, with the lower of the two at around 6Ω and the higher at of the low-frequency peaks at around 5Ω. Phase angle is really well-controlled, as you can see from the dotted black line, varying by only around + and 30. Newport Test Labs also measured the high-pass and low-pass sections of the crossover (the green and blue traces respectively) which shows they cross over at around 3Hz. measured the sensitivity of the KEF Reference 3 using its standard methodology and reported a result of 87 at one metre for a 2.83Veq input, only 0.5dB shy of KEF s specification of This means the KEF is of average efficiency overall, but perhaps a little lower than I d expect for a large floor-standing design, so I d assume KEF is applying a degree of frequency correction in the crossover. Graph 6 is a composite, melding the various different measurements made by on the one graph, and adding a new one, made by third-octave smoothing the low-frequency pink noise response before splicing it to the anechoic high-frequency response at 1.5kHz (the spliced result being the black trace on Graph 6). This shows clearly how the output of the port boosts the low frequencies, and how the traces of the bass drivers and midrange driver sum around 1Hz. You can also clearly see the crossover cutting out the midrange driver s response at a little over 3kHz (KEF puts the electrical crossover point at 2.8kHz). The KEF Reference 3s performance on the test bench was exemplary: this is a great example of an outstandingly well-designed loudspeaker that has an incredible flat and linear response across the midrange, and is well-extended into both the very lowest and very highest frequencies. S. H. 58

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