TECHNICAL FOCUS: SOUND

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1 Copyright Lighting&Sound America March 2009 Electronic Acoustic Enhancement Systems: Part One By: Alan Hardiman Above and opposite: Meyer Sound s Constellation system is used at Laboral University Auditorium in Gijon, Spain. Once seen as a controversial, lastditch contrivance of remedial acoustics an unorthodox way to salvag e an otherwise atrociously bad sounding hall electronic acoustical enhancement is on the verge of becoming widely accepted in the design of new facilities, including outdoor venues. The concept is fairly straightforward: Sounds in a venue are picked up by microphones, then, after some signal processing, are reproduced through a number of loudspeakers distributed throughout the venue to supplement, or sometimes even mask, the natural acoustics of the space. The goal is not sound reinforcement per se, which aims to provide uniform coverage of direct sound to all seating areas, although some systems can be configured for that purpose. Two systems that readers of this magazine may be most familiar with are LARES (Lexicon Acoustic Reinforcement and Enhancement System), by virtue of the sheer number of facilities that have installed it, and Meyer Sound s Constellation, which is a reboot of the LCS Audio VRAS technology acquired by Meyer in We ve been doing this for almost 20 years now, and it has taken almost that long to build up enough acceptance among users to allow an architect to design a multipurpose facility with Lares electronics handling the musical acoustics portion of acoustic perception in the hall, says Steve Barbar, president of Ecoustic Systems, which markets Lares. In ten such facilities, designed within the last seven years or so, Lares was integrated into the infrastructure from the ground up. The architecture was determined based on the ability to augment the acoustics without using architectural treatments. In other words, your seating counts can vary, seating shapes can vary, and the size of the building can be optimized geometrically, not only for what you re trying to perform but for the integration of electronics, so it yields the best costfor-performance ratios, he says. John McMahon, executive director of digital products with Meyer Sound, shares this perspective. People are now accepting these systems as being as good as or better than architectural acoustics. There are still those who have an issue with the concept in general, but we re treating it as architectural acoustics rather than as a system that fixes your room or fixes a small problem. We re changing the room architecture acoustics itself, rather than applying a band-aid on top, he says. Since electronic acoustical enhancement systems add reflections and reverberation, multipurpose halls designed with short reverberation times suitable for speech (1s or less) are obvious candidates for treatment, since electronic systems can readily be reconfigured, usually at the touch of a button, for longer reverberation times to suit other types of performance, such as baroque and chamber music (about 1.5s), classical and romantic symphonic music (about 2s), and choral and organ music (2.5s and up). Electronic acoustic enhancement is a one-way thing, says acoustician Bob Essert, director of Sound Space Design in London. We re not talking about deadening the room, but about making the room more live, with more sound envelopment. Subjectively, it sounds more resonant, warm, live, enveloping, and strong. In terms of what we hear in architectural spaces, the surfaces of the space generate sound bouncing around the room in certain ways, certain directions, certain times, and certain strengths. An electronic enhancement system can add things synthetic reflections, if you will in the direction of more strength, more warmth, more resonance, more reverberations. It cannot take an overly resonant room and dry it up. That s the job of more physical systems of ban- 88 March 2009 Lighting&Sound America

2 ners, acoustic panels or curtains that are soft and absorptive and can reduce the sound reflection properties of the room. In Part One of this investigation, we ll look at the design goals and distinguishing characteristics of six contemporary electronic acoustical enhancement systems, and their implementation in selected venues. Part Two will focus on the implications of this technology for facility owners and managers, performers and audiences, and architects and designers. Like most technological innovation, electronic acoustical enhancement has been met with mixed response and, in some quarters, considerable controversy from users and other interest groups, and therefore has real political and financial ramifications. The fact that more than 20 venues employing such systems have requested that their identities not be disclosed is mute testimony to the lack of consensus on the use of electronic acoustical enhancement. In addition to Lares and Constellation, the major players are ACS (Acoustic Control Systems), SIAP (System for Improved Acoustic Performance), AFC (Yamaha s Active Field Control), and CARMEN (from the French for Active Control of Reverberation by Natural Effect Virtual Walls). The systems are distinguished primarily by the ways in which they attempt to produce sufficient gain before feedback, a potential problem wherever loudspeakers are situated in relatively close proximity to the microphones that feed them. Feedback, and the coloration it produces, can be reduced by one or a combination of four distinct methods: placing microphones closer to the sound source; lowering the sound level by reducing system gain; increasing the number of independent channels of pickup, processing, and reproduction; and the incorporation of some form of time variance in the signal path. How the different systems employ these feedback-reduction methods accounts for the number of microphones, channels, and loudspeakers they use, as well as the type of signal processing and the placement of microphones and loudspeakers in the venue. Lares Based on the time variant reverberators developed by David Griesinger at Lexicon in the 1980s, Lares has been incorporated into more than 200 installations, making it the most widely utilized acoustical enhancement system in the world, according to Ecoustics, which notes that, of the total, Lares has been installed in 16 performing arts centers and five 20,000-seat plus sport facilities that have requested that their identities not be disclosed. Lares systems are also incorporated in Wenger Corporation s V-Room Virtual Acoustic Environment sound-isolating practice rooms and iso booths. Lares has also been installed in many religious facilities, including two with the largest pipe organs in North America the 22,000-seat Conference Center for the Church of Jesus Christ of Latter Day Saints in Salt Lake City, which has just updated its Lares system, and New York s Central Synagogue. Electronic acoustical enhancement started as a remedial fix designed to overcome known problems in architectural acoustics, Barbar says, adding that the first Lares system was designed for Toronto s historic 1,500- seat Elgin Theatre. This project is an archetypal case study of remedial electronic acoustics. Built as a vaudeville house in 1913, the Elgin suffered a slow decline over 60 years, until it came into the possession of the Ontario Heritage Trust, which closed the theatre in 1987 for a complete renovation. Since the Elgin had been designed originally for drama, its acoustics were perfectly fine for speech, but seriously lacking for anything else. The reverberation time was much too short for music, including opera, which had been staged there by Opera Atelier and the Canadian Opera Company during the years the company was planning and fund-raising for a new home. One of the goals of the renovation was to make the Elgin suitable for music, but, since it was a national historic site, no major architectural changes were permitted to the stage or auditorium. Neil Muncy, principal design consultant on the Elgin project, saw an opportunity for electronic enhancement of the theatre s acoustics. I had already been talking to David Griesinger and Steve Barbar at Lexicon about what we could do if we ever got the opportunity, so I invited them up to Toronto. Dave listened to the Elgin and said he would do the electronic enhancement for free he wanted to see it happen. So we got all the R&D done on Lexicon s nickel, and it worked the first time we turned it on. The system was successful and Lares is the most successful of any of them because of its ability to squeeze out more gain before feedback than any other approach. Dave Griesinger s brilliant programming with time variance did that. By continuously varying the initial delay times by a very small amount, he was able to prevent the system from going into oscillation and feeding back when the level went above unity gain, Muncy recalls. The problem with some of the other systems is that you can t hear them until the music stops, he adds. If you can t hear the reverberation while the music is playing, it really doesn t solve the problem. You ve got microphones feeding loudspeakers, with a bunch of stuff in between, and you can t get enough gain before feed- Photos: Courtesy of Meyer Sound March

3 The Pritzker Pavilion in Chicago s Millennium Park uses a Lares system. back to hear the reverb along with the music all the time. At the Elgin, two Brüel & Kjaer 4011 mics, mounted on booms about 3' out from the face of the balconies and angled in slightly, feed two Lexicon 480-based Lares mainframes, the outputs of which feed 26 Ramsa power amp channels driving 116 almost invisible ceiling-mounted Paradigm 3SE Mini loudspeakers, 60 of which are under the balcony, where the natural acoustics were dreadful. In an AES paper on the Elgin installation delivered shortly after its completion, Griesinger noted that the number of microphones and speaker banks used in the Elgin Theatre was primarily determined by the hardware of the reverberators. Using two Lares processors gives us eight output channels, allows internal mixing from two input channels, and runs 16 reverberators. The Lares processors supply all the time delays, so no additional digital electronics are needed. The Lares processors are controlled remotely by a single Lexicon MRC MIDI controller. The eight outputs are directed to eight banks of loudspeakers, which are arranged in an interleaved pattern we call a tiling. No two adjacent loudspeakers are driven from the same output. This lack of coherence between the loudspeakers increases the apparent diffusion of the system and reduces coloration. A tiling of this type requires at least four output channels, and this number is the minimum we recommend for this type of installation. We were concerned at first that we would need speakers on the side walls. However, we correctly decided that dense ceiling arrays would form image sources well beyond the wall, and lateral energy would be adequate. He also notes that basing the system on time variant processing greatly increases the apparent number of channels, which is ideally the product of the number of microphones and the number of speaker banks. This product is exceedingly important. Microphones are expensive and unsightly. By using a small number of them and a large number of relatively inexpensive electronic reverberators, the system can be made much more practical. Not only that, but because varying the delays broadens resonant peaks in the room, gain before feedback can be increased theoretically by at least 8dB over non-time-variant systems. Muncy reports the gain was closer to 20dB at the Elgin. Muncy, Griesinger, and Barbar got a second chance to implement Lares in Toronto in 1996 at the 3,187-seat O Keefe Centre later known as the Hummingbird and now the Sony Centre where the necessary architectural overhaul to improve its execrable acoustics was estimated at some $60-70 million, and so was out of the question for financial reasons. This venue was also used by the Canadian Opera Company at the time. One of the problems was a reflection from the rear concave wall back to the stage a quarter of a second later at a higher level than the direct sound. There were no significant firstorder reflections coming off the side walls at all to provide a sense of space, so we got RPG to create a special kind of diffuser to fit the wood side walls, and we put about 50 loudspeakers on each of the two side walls, Muncy explains. The remainder of the 288 loudspeakers are in the ceilings. We were able to tweak the Lares so you got first-order sound from the walls before the main wave front even hit the back. The back-slap was still there, but it was masked by all the other stuff that was now coming in as a result of the Lares output. Of course, this required considerable gain before feedback to accomplish. In contrast to the high estimate for architectural renovation, the Lares system cost a mere $450,000, and was so warmly received by critics that its presence was finally acknowledged 18 months later. The splendid acoustics are a gift of the Lares sound-reinforcement system, installed last year, wrote critic David Lasker in The Globe and Mail. Now, everyone at the Hummingbird has a good seat. Lares outdoors In addition to its use in performing arts centers and other indoor facilities, Lares has also been applied successfully in outdoor venues. The first such application came in 1995, when a Lares system was used at the Vienna Festival. An audience of some 30,000 heard Zubin Mehta conduct the Vienna Philharmonic in a performance of Beethoven s Symphony No. 9, complete with early reflections and rever- Photo: Courtesy of Lexicon 90 March 2009 Lighting&Sound America

4 beration characteristic of a concert hall. This trial was so successful that the system was subsequently purchased for use annually at the festival. Lares was also used four years later in an outdoor production of Puccini s Turandot at China s Imperial Shrine. In 2004, the Jay Pritzker Pavilion in Chicago s Millennium Park became the first outdoor venue in the U.S. to have a permanent Lares system installed. Designed by the architect Frank Gehry, the pavilion employs a trellis for suspending loudspeakers, both for Lares as well as for sound reinforcement, enabling them to be precisely placed and carefully oriented, with no visual obstructions. In addition, it creates a visual canopy that unifies a fixed seating area for 4,000 spectators, with a lawn accommodating another 7,000. The stage is equipped both with an orchestra shell and a dedicated Lares system to adjust stage acoustics, enabling all members of the orchestra to hear each other well in an outdoor setting, an otherwise unattainable condition. It should be noted that only systems in which the signal processing generates artificial reflections and reverberation, such as Lares, are appropriate for such use outdoors. By contrast, systems in which the natural reflections and reverberation of a venue are picked up and regenerated through loudspeakers are not suitable, since there is little or no such reverberation outdoors to being with. In recent years, Lares has been migrated from Lexicon s original 480 studio digital reverberator to the newer 960 platform, and its catalog offerings have been augmented with purpose-built microphone preamps, power amplifiers, and loudspeakers. Two days of regional business, networking and learning. Over 80 exhibitors across two halls. The Royal Armouries: Leeds April 2009 Register for free now at afo CIRCLE READER SERVICE 52 Constellation Constellation is based on the VRAS (Variable Room Acoustic System) technology developed by Mark Poletti, of Industrial Research Ltd. in New Zealand. VRAS was licensed to LCS Audio in 1997, who installed a number of VRAS systems using the Matrix3 digital audio control platform. The system is capable of generating multichannel reverberation and early reflections, as well as mixing, processing, and routing them. LCS Audio was acquired by Meyer Sound in 2005, and VRAS became an integral part of Meyer s Constellation electroacoustic architecture. Constellation is based on the principle of multichannel gain, says McMahon, who, prior to joining Meyer, was CEO of LCS Audio. In a really simple example, if you have microphones open to a loudspeaker in a room, you ve marginally decreased the absorption of that room. If you repeat that and keep those microphones and loudspeakers decorrelated, eventually you can decrease the absorption of the room enough that it starts to extend the reverberation time. The key in that is keeping them decorrelated, and that s done both through position and through the algorithm. Our systems typically have 40 channels on average, so we can achieve that reduction in absorption of the hall, he says. Constellation is a regenerative system, he continues. Rather than being an in-line type of system where we put 92 March 2009 Lighting&Sound America

5 microphones near the performers and then overlay some reverberation onto those signals and deliver that to the audience, we have many microphones in the audience area, so we re actually changing the acoustics of the hall itself. We also place microphones over the stage and, in some cases, laterally on the stage and those are used to generate early reflections out to the audience. So our system is both an inline system and a non-inline system. Both regenerative and non-regenerative components are used. The regenerative non-inline part is used for reverberation enhancement, and the inline non-regenerative part is used for early reflection enhancement. Constellation in its own right has been deployed in some 14 installations, in addition to those completed earlier under the auspices of LCS Audio. The most notable examples are the 1,400-seat Laboral University Auditorium in Gijon, Spain, and the 2,014-seat Zellerbach Hall at the University of California, Berkeley. Zellerbach Hall is home to Cal Performances, the largest presenter of performing arts in the San Francisco Bay Area. Cal Performances presents a wide range of programming, including orchestral, chamber music, jazz, theatrical, dance, spoken word, opera, and a variety of ethnic performances from around the world, making it the classic multipurpose venue. This diversity of program material imposes immense demands on the hall s acoustics, because the needs of orchestral music, plays, and recitals are quite different. Furthermore, the labor involved in erecting and striking the orchestra shell on consecutive days to suit diverse performances would give Sisyphus a run for his money. There is a great demand now for venues like Zellerbach Hall to be multipurpose, said John Meyer, president and CEO of Meyer Sound, on the completion of the project. That creates a real challenge: How can one room be made to sound right for many different kinds of performances? It seemed to me that the answer for existing venues like Zellerbach was in good planning and appropriate use of digital technology in harmony with existing acoustics. Our VRAS technology gave us the core of what we needed to solve this puzzle, and we went from there. The system is said to allow an audience to experience a music concert with all of the warmth and resonance of a concert hall, while a play in the same space exhibits increased intelligibility. Musicians enjoy an improved ability to hear each other, creating an onstage acoustical experience conducive to ensemble playing. ACS Developed in the Netherlands in conjunction with the Delft University of Technology, ACS uses the multiple-channel approach to increase system gain before feedback. Each channel provides only a small contribution to the total sound field, but, in aggregate, the total level is appreciable. Typically, microphones, placed relatively close to the stage or other sound source, feed a matrix of delays through a rack as large as 96 inputs by 96 outputs; racks The ETCP Certification Council proudly welcomes and We welcome you to the Council as ETCP enters the next phase of its growth. We are pleased to add your voices to the leadership of this industrywide effort to promote safety, improve practice and recognize our industry s most qualified entertainment technicians. ETCP Certification Council Organizational Members Business Members ESTA IATSE TEA BASE Entertainment AMPTP InfoComm USITT Broadway Across America CITT IAAM The League SHAPE Cirque du Soleil/ MGM MIRAGE Live Nation Production Resource Group Setting the stage for safety. etcp.esta.org Special thanks to our top contributors and media partners: Top contributors: IATSE, Live Nation, Production Resource Group and USITT. Media partners: Church Production; Exhibit Builder; Lighting&Sound America; Live Design; Pollstar; Projection, Lights and Staging News; Protocol; Rental & Staging Systems; Systems Contractor News; Technologies for Worship; and Theatre Design & Technology. ESTA AMPTP CITT IAAM IATSE INFOCOMM THE LEAGUE SHAPE TEA USITT CIRCLE READER SERVICE 53 March

6 can be cascaded for even more I/O. The matrix is designed to provide delays, sound paths, and image sources that would exist in a larger virtual or ideal hall mapped around the existing one. Because the reverberant sound further from the stage is not picked up anywhere near as strongly as the direct sound, independent multi-channel processors are used to provide separate control over early reflections and the later onset of reverberation. Recognizing that direct sound is important for both intelligibility and localization of performers for the audience, ACS designers are careful to delay the signal appropriately to synthesize early reflections (20 to ms) for clarity, presence, spaciousness, and envelopment, and then provide additional reverberation (longer than ms) to provide warmth in the low end, and brilliance and fullness of tone at higher frequencies. Since the microphones are placed fairly close to the sound source, they can be also be used for recording and hearing impaired systems, and to synthesize a virtual orchestra shell for the performers, using a separate array of loudspeakers around the stage. It is as if there were walls surrounding them. Musicians can better hear each other, thus the ensemble playing conditions are improved, according to ACS. If the performers are in a pit, as is the case with many stage shows, this part of the system can be used for foldback monitoring, enabling the performers to hear themselves better and, as ACS puts it, to play lighter. Acoustic Control Systems published client list includes 47 installations in halls around the world. While most are in Europe, such as the 1,000- seat Barbican Centre in London, ACS is also installed in the 2,779-seat New York State Theatre at the Lincoln Center, and the 2,325-seat National Arts Centre in Ottawa. ACS asserts, It is a proven fact that the ACS system makes your hall benefit from more performances and more seats sold. Small 700-seat venues with a reverberation time of only 1.0 second become opera houses, concert halls, and musical theatres at the flick of a button. Your hall becomes restricted by your imagination and the talent of your artists only! Implementing an ACS system very often leads to cost savings in the redecoration or rebuilding process of existing halls and theatres as well as for newly designed halls. Fact is that, in nature, sound within a venue is transferred in many, many directions. One can say acoustics is truly multi-channel. This can of course only be simulated with a larger number of channels. CIRCLE READER SERVICE 54 SIAP Also developed in the Netherlands, SIAP has gone through four iterations, and boasts an installed base of some 35 permanent systems, primarily in Europe. Notable examples on this side of the Atlantic include the 1,100-seat Vivian Beaumont Theatre at Lincoln Centre, the 2,500-seat Ahmanson Theatre in Los Angeles, and the 9,100- seat Southeast Christian Church in Louisville, Kentucky. 94 March 2009 Lighting&Sound America

7 SIAP is distributed in the USA by RPG Systems, whose website contains few substantive details about the system, aside from a two-page brochure and the scanned image of a printed document from 1997 entitled, The History of Electronic Architecture and Variable Acoustics, co-authored by SIAP s Wim Prinssen and RPG Systems president Peter D Antonio. According to Tom Ryan, manager of RPG s audio-visual integration division, this is due to the fact that the system underwent a new development phase at the end of last year, so we haven t yet got much of the new marketing material to update the website. It s now called the Mark IV system. SIAP has teamed up with Sonic Emotion for waveform synthesis, giving it three levels of performance in that waveform synthesis-based system. The first level is architectural acoustic enhancement, which is the basic function of the SIAP, Ryan says. Levels Two and Three are more for effect, with Level Two providing twodimensional image steering, where you can get precise surround sound, typically synchronized to video media. Level Three is a full, three-dimensional blanketing effect. If you had a 3-D image on screen, it would feel like actual sound sources were going through you. SIAP uses a multichannel approach to control feedback, with 32 outputs, expandable to 64. Each output has its own unique impulse response, and they are non-correlated, so adjacent speakers are not getting the same signals, Ryan says. SIAP uses a combination of non-time variance and time variance it depends on how you set up the processor. It has taken VRAS a step further, due to the way it processes these non-correlated outputs. It s a much more natural approach in the sense that, since you have decorrelated outputs, you get a more natural reflection, just as each different surface would not have the same impulse response naturally. Three SIAP Mark IV systems have been installed in South Korea; four more are planned for churches in the U.S. AFC Yamaha s AFC is a control technology that uses acoustic feedback, rather than electronically generated synthetic reflections and reverberation. AFC is designed to enable the improvement of important items concerning auditory impressions while maintaining the natural architectural sound that the room originally has, according to Yamaha. While it is necessary to have a large amount of energy feedback for a system based on feedback to provide a large effect, AFC manages to Now UL Listed increase gain before feedback by applying both time variance and electronic microphone rotation; that is, the I/O routing is altered periodically. AFC is scalable for use in venues of different sizes, such as small 300-seat theatres (four microphones, two processors, and 12 loudspeakers) to larger 4,000-seat venues (eight microphones, four processors, and 96 loudspeakers). Its stated goals include extending reverberation time, increasing sound pressure levels, improving the sound field in under-balcony areas, Operator Friendly Ergonomics Ultimate in Precision Optics Metal Halide Light Source Not since the introduction of the legendary Strong Super Trouper in 1956 has so much d esign innovation and user feedback been merged into true revolutionary functionality. CIRCLE READER SERVICE 55 March

8 improving stage acoustics, and exchanging sound energy between the stage and audience area for uniformity. Like Lares, it is also intended for use in practice rooms and other small performance spaces. An AFC system consists of at least two AFC1 units, one of which is used for signal processing, and the other for output control. Each AFC1 has eight input channels and 32 output channels; the system can be expanded to 96 output channels by cascading three AFC1 units for output control and connecting them to one AFC1 unit for signal processing. Systems with four processors facilitate zoning in larger venues. Microphones hung from the ceiling at or around the critical distance where reflected energy is equal to direct energy are used to pick up diffused sound. Purpose-built loudspeakers are aimed horizontally or upwards, more than the critical distance away from the audience area, in order to contribute to the diffuse field. According to Yamaha, AFC has been installed in more than 30 venues, mostly in Japan. Projects in the U.S. include an AFC-based renovation of the 3,485-seat Miller Auditorium at Western Michigan University in Kalamazoo, the 400-seat Church of St. Michael and St. George in St. Louis, Missouri, and the 800-seat Vestal High School Auditorium in Vestal, New York. IT SINGS WITHOUT ANYONE ON STAGE Old Town School of Folk Music - Chicago Chicago Minneapolis schulershook.com Dallas CIRCLE READER SERVICE 56 Carmen Carmen comprises a number of electro-acoustic active cells (approximately from 16 to 40), each of them being composed of a microphone, an electronic filtering unit, a power amplifier, and a loudspeaker. Placed around the walls and ceiling of the auditorium, the cells form virtual walls, depending on the architecture and the acoustic problem to solve. They only communicate between each other by the acoustic way. The whole cells are controlled by a computer or an on-stage remote control panel, according to information supplied by France s Centre Scientifique et Technique du Bâtiment (CSTB), which developed the system. The innovative layout of the microphones and loudspeakers produces completely natural acoustics with a space-time coherence of the sound field preserved. Reverberation enhancement is simply coming from the mutual reflections between the different parts of the virtual walls, as for real walls in a room. No microphone on stage is impeding the normal use of the space above the stage. Besides, the natural directivity of the sound sources, and stage sound images cannot be altered, as when picking up the sound from above the head of the musicians or close to stage and reproducing just as it is whatever the place in the hall. Acoustician Bob Essert is of the opinion that in terms of quality, Carmen is a principal player. CTSB s client list includes nine facilities in France and Monaco, with the exception of the 1,900-seat Brighton Dome in the U.K. That system, completed in 2002, features 30 cells, including an active orchestra ceiling reflector, and is programmed with presets for chamber music, opera, and symphonic works. System costs The cost of installing an electronic acoustical enhancement system is widely variable, with venue size being apparently a much more significant factor than the selection of any particular system. From what I have been able to gather, a complete system, including installation, would rarely exceed the $1M dollar mark, and typically would be less than half that. This represents an enormous cost saving over equivalent physical architecture renovation in the case of remedial acoustical work. In the construction of new multipurpose venues or smaller facilities in these times of belt-tightening and cost constraints, it may also represent an offer you can t refuse. Next month, we ll continue with a look at how electronic acoustical enhancement systems have been received by members of the industry, performing arts, and general public. 96 March 2009 Lighting&Sound America