Ls a 0903 Electronic Acoustics

Once seen as a controversial, last-ditch contrivance of remedialacoustics—an unorthodox way to sal-vag e an otherwise atrociously badsounding hall—electronic acousticalenhancement is on the verge ofbecoming widely accepted in thedesign of new facilities, including out-door venues.The concept is fairly straightfor-

ward: Sounds in a venue are pickedup by microphones, then, after somesignal processing, are reproducedthrough a number of loudspeakers dis-tributed throughout the venue to sup-plement, or sometimes even mask, thenatural acoustics of the space. Thegoal is not sound reinforcement perse, which aims to provide uniform cov-erage of direct sound to all seatingareas, although some systems can beconfigured for that purpose.Two systems that readers of this

magazine may be most familiar withare LARES (Lexicon AcousticReinforcement and EnhancementSystem), by virtue of the sheer numberof facilities that have installed it, andMeyer Sound’s Constellation, which is

a “reboot” of the LCS Audio VRAStechnology acquired by Meyer in 2005.“We’ve been doing this for almost

20 years now, and it has taken almostthat long to build up enough accept-ance among users to allow an archi-tect to design a multipurpose facilitywith Lares electronics handling themusical acoustics portion of acousticperception in the hall,” says SteveBarbar, president of Ecoustic Systems,which markets Lares.In ten such facilities, designed with-

in the last seven years or so, Lareswas integrated into the infrastructurefrom the ground up. “The architecturewas determined based on the ability toaugment the acoustics without usingarchitectural treatments. In otherwords, your seating counts can vary,seating shapes can vary, and the sizeof the building can be optimized geo-metrically, not only for what you’re try-ing to perform but for the integration ofelectronics, so it yields the best cost-for-performance ratios,” he says.John McMahon, executive director

of digital products with Meyer Sound,shares this perspective. “People are

now accepting these systems asbeing as good as or better than archi-tectural acoustics. There are stillthose who have an issue with theconcept in general, but we’re treatingit as architectural acoustics ratherthan as a system that fixes your roomor fixes a small problem. We’rechanging the room architectureacoustics itself, rather than applying aband-aid on top,” he says.Since electronic acoustical

enhancement systems add reflectionsand reverberation, multipurpose hallsdesigned with short reverberation timessuitable for speech (1s or less) areobvious candidates for treatment, sinceelectronic systems can readily bereconfigured, usually at the touch of abutton, for longer reverberation timesto suit other types of performance,such as baroque and chamber music(about 1.5s), classical and romanticsymphonic music (about 2s), andchoral and organ music (2.5s and up).“Electronic acoustic enhancement

is a one-way thing,” says acousticianBob Essert, director of Sound SpaceDesign in London. “We’re not talkingabout deadening the room, but aboutmaking the room more live, with moresound envelopment. Subjectively, itsounds more resonant, warm, live,enveloping, and strong. In terms ofwhat we hear in architectural spaces,the surfaces of the space generatesound bouncing around the room incertain ways, certain directions, certaintimes, and certain strengths. An elec-tronic enhancement system can addthings—synthetic reflections, if youwill—in the direction of more strength,more warmth, more resonance, morereverberations. It cannot take an overlyresonant room and dry it up. That’s thejob of more physical systems of ban-

88 • March 2009 • Lighting&Sound America

TECHNICAL FOCUS: SOUND

Electronic AcousticEnhancement Systems:Part OneBy: Alan Hardiman

Above and opposite: Meyer Sound’s Constellation system is used at Laboral UniversityAuditorium in Gijon, Spain.

Copyright Lighting&Sound America March 2009 http://www.lightingandsoundamerica.com/LSA.html

ners, acoustic panels or curtains thatare soft and absorptive and canreduce the sound reflection propertiesof the room.”In Part One of this investigation,

we’ll look at the design goals and dis-tinguishing characteristics of six con-temporary electronic acousticalenhancement systems, and theirimplementation in selected venues.Part Two will focus on the implica-

tions of this technology for facilityowners and managers, performers andaudiences, and architects and design-ers. Like most technological innova-tion, electronic acoustical enhance-ment has been met with mixedresponse—and, in some quarters,considerable controversy—from usersand other interest groups, and there-fore has real political and financialramifications. The fact that more than20 venues employing such systemshave requested that their identities notbe disclosed is mute testimony to thelack of consensus on the use of elec-tronic acoustical enhancement.In addition to Lares and

Constellation, the major players areACS (Acoustic Control Systems),SIAP (System for Improved AcousticPerformance), AFC (Yamaha’s ActiveField Control), and CARMEN (fromthe French for Active Control ofReverberation by Natural EffectVirtual Walls).The systems are distinguished pri-

marily by the ways in which theyattempt to produce sufficient gainbefore feedback, a potential problemwherever loudspeakers are situated inrelatively close proximity to the micro-phones that feed them. Feedback, andthe coloration it produces, can bereduced by one—or a combination—offour distinct methods: placing micro-phones closer to the sound source;lowering the sound level by reducingsystem gain; increasing the number ofindependent channels of pickup, pro-cessing, and reproduction; and theincorporation of some form of timevariance in the signal path.How the different systems employ

these feedback-reductionmethodsaccounts for the number of microphones,

channels, and loudspeakers they use, aswell as the type of signal processing andthe placement of microphones and loud-speakers in the venue.

LaresBased on the time variant reverbera-tors developed by David Griesinger atLexicon in the 1980s, Lares has beenincorporated into more than 200 instal-lations, making it “the most widely uti-lized acoustical enhancement systemin the world,” according to Ecoustics,which notes that, of the total, Lareshas been installed in 16 performingarts centers and five 20,000-seat plussport facilities that have requested thattheir identities not be disclosed. Laressystems are also incorporated inWenger Corporation’s V-Room VirtualAcoustic Environment sound-isolatingpractice rooms and iso booths.Lares has also been installed in

many religious facilities, includingtwo with the largest pipe organs inNorth America—the 22,000-seatConference Center for the Church ofJesus Christ of Latter Day Saints inSalt Lake City, which has just updat-ed its Lares system, and New York’sCentral Synagogue.“Electronic acoustical enhancement

started as a remedial fix designed toovercome known problems in architec-tural acoustics,” Barbar says, addingthat the first Lares system wasdesigned for Toronto’s historic 1,500-seat Elgin Theatre. This project is anarchetypal case study of remedialelectronic acoustics. Built as a vaude-ville house in 1913, the Elgin suffered aslow decline over 60 years, until itcame into the possession of theOntario Heritage Trust, which closedthe theatre in 1987 for a complete ren-ovation. Since the Elgin had beendesigned originally for drama, itsacoustics were perfectly fine forspeech, but seriously lacking for any-thing else. The reverberation time wasmuch too short for music, includingopera, which had been staged thereby Opera Atelier and the CanadianOpera Company during the years thecompany was planning and fund-rais-ing for a new home. One of the goals

of the renovation was to make theElgin suitable for music, but, since itwas a national historic site, no majorarchitectural changes were permittedto the stage or auditorium.Neil Muncy, principal design con-

sultant on the Elgin project, saw anopportunity for electronic enhance-ment of the theatre’s acoustics. “I had

already been talking to DavidGriesinger and Steve Barbar atLexicon about what we could do if weever got the opportunity, so I invitedthem up to Toronto. Dave listened tothe Elgin and said he would do theelectronic enhancement for free—hewanted to see it happen. So we got allthe R&D done on Lexicon’s nickel, andit worked the first time we turned it on.The system was successful—andLares is the most successful of any ofthem—because of its ability tosqueeze out more gain before feed-back than any other approach. DaveGriesinger’s brilliant programming withtime variance did that. By continuouslyvarying the initial delay times by a verysmall amount, he was able to preventthe system from going into oscillationand feeding back when the level wentabove unity gain,” Muncy recalls.“The problem with some of the

other systems is that you can’t hearthem until the music stops,” he adds.“If you can’t hear the reverberationwhile the music is playing, it reallydoesn’t solve the problem. You’ve gotmicrophones feeding loudspeakers,with a bunch of stuff in between, andyou can’t get enough gain before feed-

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back to hear the reverb along with themusic all the time.”At the Elgin, two Brüel & Kjaer 4011

mics, mounted on booms about 3' outfrom the face of the balconies andangled in slightly, feed two Lexicon480-based Lares mainframes, the out-puts of which feed 26 Ramsa poweramp channels driving 116 almostinvisible ceiling-mounted Paradigm3SE Mini loudspeakers, 60 of whichare under the balcony, where the natu-ral acoustics were dreadful.In an AES paper on the Elgin instal-

lation delivered shortly after its com-pletion, Griesinger noted that “thenumber of microphones and speakerbanks used in the Elgin Theatre wasprimarily determined by the hardwareof the reverberators. Using two Laresprocessors gives us eight outputchannels, allows internal mixing fromtwo input channels, and runs 16 rever-berators. The Lares processors supplyall the time delays, so no additionaldigital electronics are needed. TheLares processors are controlledremotely by a single Lexicon MRCMIDI controller. The eight outputs aredirected to eight banks of loudspeak-ers, which are arranged in an inter-leaved pattern we call a tiling. No twoadjacent loudspeakers are driven fromthe same output. This lack of coher-

ence between the loudspeakersincreases the apparent diffusion of thesystem and reduces coloration. A tilingof this type requires at least four out-put channels, and this number is theminimum we recommend for this typeof installation. We were concerned atfirst that we would need speakers onthe side walls. However, we correctlydecided that dense ceiling arrayswould form image sources wellbeyond the wall, and lateral energywould be adequate.”He also notes that basing the sys-

tem on time variant processing greatlyincreases the apparent number ofchannels, “which is ideally the productof the number of microphones and thenumber of speaker banks. This prod-uct is exceedingly important.Microphones are expensive andunsightly. By using a small number ofthem and a large number of relativelyinexpensive electronic reverberators,the system can be made much morepractical.” Not only that, but becausevarying the delays broadens resonantpeaks in the room, gain before feed-back can be increased theoretically byat least 8dB over non-time-variant sys-tems. Muncy reports the gain wascloser to 20dB at the Elgin.Muncy, Griesinger, and Barbar got a

second chance to implement Lares in

Toronto in 1996 at the 3,187-seatO’Keefe Centre—later known as theHummingbird and now the SonyCentre—where the necessary architec-tural overhaul to improve its execrableacoustics was estimated at some $60-70 million, and so was out of the ques-tion for financial reasons. This venuewas also used by the Canadian OperaCompany at the time. One of the prob-lems was a reflection from the rearconcave wall back to the stage a quar-ter of a second later at a higher levelthan the direct sound.“There were no significant first-

order reflections coming off the sidewalls at all to provide a sense ofspace, so we got RPG to create aspecial kind of diffuser to fit the woodside walls, and we put about 50 loud-speakers on each of the two sidewalls,” Muncy explains. “The remain-der of the 288 loudspeakers are in theceilings. We were able to tweak theLares so you got first-order soundfrom the walls before the main wavefront even hit the back. The back-slapwas still there, but it was masked byall the other stuff that was now comingin as a result of the Lares output.” Ofcourse, this required considerable gainbefore feedback to accomplish.In contrast to the high estimate for

architectural renovation, the Laressystem cost a mere $450,000, andwas so warmly received by critics thatits presence was finally acknowledged18 months later. “The splendidacoustics are a gift of the Laressound-reinforcement system, installedlast year,” wrote critic David Lasker inThe Globe and Mail. “Now, everyoneat the Hummingbird has a good seat.”

Lares outdoorsIn addition to its use in performing artscenters and other indoor facilities,Lares has also been applied success-fully in outdoor venues. The first suchapplication came in 1995, when aLares system was used at the ViennaFestival. An audience of some 30,000heard Zubin Mehta conduct the ViennaPhilharmonic in a performance ofBeethoven’s Symphony No. 9, com-plete with early reflections and rever-

The Pritzker Pavilion in Chicago’s Millennium Park uses a Lares system.

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beration characteristic of a concert hall. This trial was sosuccessful that the system was subsequently purchased foruse annually at the festival. Lares was also used four yearslater in an outdoor production of Puccini’s Turandot atChina’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 apermanent Lares system installed. Designed by the architectFrank Gehry, the pavilion employs a trellis for suspendingloudspeakers, both for Lares as well as for sound reinforce-ment, enabling them to be precisely placed and carefully ori-ented, with no visual obstructions. In addition, it creates avisual canopy that unifies a fixed seating area for 4,000 spec-tators, with a lawn accommodating another 7,000. The stageis equipped both with an orchestra shell and a dedicatedLares system to adjust stage acoustics, enabling all mem-bers of the orchestra to hear each other well in an outdoorsetting, 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. Bycontrast, systems in which the natural reflections and rever-beration of a venue are picked up and regenerated throughloudspeakers are not suitable, since there is little or no suchreverberation outdoors to being with.In recent years, Lares has been migrated from Lexicon’s

original 480 studio digital reverberator to the newer 960platform, and its catalog offerings have been augmentedwith purpose-built microphone preamps, power amplifiers,and loudspeakers.

ConstellationConstellation is based on the VRAS (Variable RoomAcoustic System) technology developed by Mark Poletti, ofIndustrial Research Ltd. in New Zealand. VRAS waslicensed to LCS Audio in 1997, who installed a number ofVRAS systems using the Matrix3 digital audio control plat-form. The system is capable of generating multichannelreverberation and early reflections, as well as mixing, pro-cessing, and routing them. LCS Audio was acquired byMeyer Sound in 2005, and VRAS became an integral partof Meyer’s Constellation electroacoustic architecture.“Constellation is based on the principle of multichannel

gain,” says McMahon, who, prior to joining Meyer, was CEOof LCS Audio. “In a really simple example, if you havemicrophones open to a loudspeaker in a room, you’ve mar-ginally decreased the absorption of that room. If you repeatthat and keep those microphones and loudspeakers decor-related, eventually you can decrease the absorption of theroom enough that it starts to extend the reverberation time.The key in that is keeping them decorrelated, and that’sdone both through position and through the algorithm. Oursystems typically have 40 channels on average, so we canachieve 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

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microphones near the performers and then overlay somereverberation onto those signals and deliver that to theaudience, we have many microphones in the audiencearea, so we’re actually changing the acoustics of the hallitself. We also place microphones over the stage—and, insome cases, laterally on the stage—and those are used togenerate early reflections out to the audience. So our sys-tem is both an inline system and a non-inline system. Bothregenerative and non-regenerative components are used.The regenerative non-inline part is used for reverberationenhancement, and the inline non-regenerative part is usedfor early reflection enhancement.”Constellation in its own right has been deployed in some

14 installations, in addition to those completed earlier underthe auspices of LCS Audio. The most notable examples arethe 1,400-seat Laboral University Auditorium in Gijon,Spain, and the 2,014-seat Zellerbach Hall at the Universityof California, Berkeley. Zellerbach Hall is home to CalPerformances, the largest presenter of performing arts inthe San Francisco Bay Area. Cal Performances presents awide range of programming, including orchestral, chambermusic, jazz, theatrical, dance, spoken word, opera, and avariety of ethnic performances from around the world, mak-ing it the classic multipurpose venue.This diversity of program material imposes immense

demands on the hall’s acoustics, because the needs oforchestral music, plays, and recitals are quite different.Furthermore, the labor involved in erecting and striking theorchestra shell on consecutive days to suit diverse perform-ances 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 andCEO of Meyer Sound, on the completion of the project.“That creates a real challenge: How can one room be madeto sound right for many different kinds of performances? Itseemed to me that the answer for existing venues likeZellerbach was in good planning and appropriate use ofdigital technology in harmony with existing acoustics. OurVRAS technology gave us the core of what we needed tosolve 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 aconcert hall, while a play in the same space exhibitsincreased intelligibility. Musicians enjoy an improved abilityto hear each other, creating an onstage acoustical experi-ence conducive to ensemble playing.

ACSDeveloped in the Netherlands in conjunction with the DelftUniversity of Technology, ACS uses the multiple-channelapproach to increase system gain before feedback. Eachchannel provides only a small contribution to the totalsound field, but, in aggregate, the total level is appreciable.Typically, 12-36 microphones, placed relatively close to thestage or other sound source, feed a matrix of delaysthrough a rack as large as 96 inputs by 96 outputs; racks

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can be cascaded for even more I/O.The matrix is designed to providedelays, sound paths, and imagesources that would exist in a larger vir-tual or ideal hall mapped around theexisting one.Because the reverberant sound fur-

ther from the stage is not picked upanywhere near as strongly as thedirect sound, independent multi-chan-nel processors are used to provideseparate control over early reflectionsand the later onset of reverberation.Recognizing that direct sound is

important for both intelligibility andlocalization of performers for the audi-ence, ACS’ designers are careful todelay the signal appropriately to syn-thesize early reflections (20 to 80-100ms) for clarity, presence, spacious-ness, and envelopment, and then pro-vide additional reverberation (longerthan 80-100ms) to provide warmth inthe low end, and brilliance and fullnessof tone at higher frequencies.Since the microphones are placed

fairly close to the sound source, theycan be also be used for recording and

hearing impaired systems, and to syn-thesize a “virtual orchestra shell” forthe performers, using a separate arrayof loudspeakers around the stage. It is“as if there were walls surroundingthem. Musicians can better hear eachother, thus the ensemble playing con-ditions are improved,” according toACS. If the performers are in a pit, asis the case with many stage shows,this part of the system can be used forfoldback monitoring, enabling the per-formers to hear themselves better and,as ACS puts it, to “play lighter.”Acoustic Control Systems’ pub-

lished client list includes 47 installa-tions in halls around the world. Whilemost are in Europe, such as the 1,000-seat Barbican Centre in London, ACSis also installed in the 2,779-seat NewYork State Theatre at the LincolnCenter, and the 2,325-seat NationalArts Centre in Ottawa.ACS asserts, “It is a proven fact that

the ACS system makes your hall bene-fit from more performances and moreseats sold. Small 700-seat venues witha reverberation time of only 1.0 secondbecome opera houses, concert halls,and musical theatres at the flick of abutton. Your hall becomes restricted byyour imagination and the talent of yourartists only! Implementing an ACS sys-tem very often leads to cost savings inthe redecoration or rebuilding processof existing halls and theatres as wellas for newly designed halls. Fact isthat, in nature, sound within a venueis transferred in many, many direc-tions. One can say acoustics is truly‘multi-channel.’ This can of courseonly be simulated with a larger num-ber of channels.”

SIAPAlso developed in the Netherlands,SIAP has gone through four iterations,and boasts an installed base of some35 permanent systems, primarily inEurope. Notable examples on this sideof the Atlantic include the 1,100-seatVivian Beaumont Theatre at LincolnCentre, the 2,500-seat AhmansonTheatre in Los Angeles, and the 9,100-seat Southeast Christian Church inLouisville, Kentucky.C

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SIAP is distributed in the USA byRPG Systems, whose website con-tains few substantive details about thesystem, aside from a two-pagebrochure and the scanned image of aprinted document from 1997 entitled,The History of Electronic Architectureand Variable Acoustics, co-authoredby SIAP’s Wim Prinssen and RPGSystems president Peter D’Antonio.According to Tom Ryan, manager of

RPG’s audio-visual integration division,this is due to the fact that “the systemunderwent a new development phaseat the end of last year, so we haven’tyet got much of the new marketingmaterial to update the website. It’snow called the Mark IV system. SIAPhas teamed up with Sonic Emotion forwaveform synthesis, giving it three lev-els of performance in that waveformsynthesis-based system.“The first level is architectural

acoustic enhancement, which is thebasic function of the SIAP,” Ryan says.“Levels Two and Three are more foreffect, with Level Two providing two-dimensional image steering, where youcan get precise surround sound, typi-cally synchronized to video media.Level Three is a full, three-dimensionalblanketing effect. If you had a 3-Dimage on screen, it would feel likeactual sound sources were goingthrough you.”SIAP uses a multichannel approach

to control feedback, with 32 outputs,expandable to 64. “Each output has itsown unique impulse response, andthey are non-correlated, so adjacentspeakers are not getting the same sig-nals,” Ryan says. “SIAP uses a combi-nation of non-time variance and timevariance—it depends on how you setup the processor. It has taken VRAS astep further, due to the way it process-es these non-correlated outputs. It’s amuch more natural approach in thesense that, since you have decorrelat-ed outputs, you get a more natural‘reflection,’ just as each different sur-face would not have the same impulseresponse naturally.” Three SIAP MarkIV systems have been installed inSouth Korea; four more are plannedfor churches in the U.S.

AFCYamaha’s AFC is a control technologythat uses acoustic feedback, ratherthan electronically generated syntheticreflections and reverberation. AFC isdesigned to enable the improvementof “important items concerning audito-ry impressions while maintaining thenatural architectural sound that theroom originally has,” according toYamaha. While it is necessary to havea large amount of energy feedback fora system based on feedback to pro-vide a large effect, AFC manages to

increase gain before feedback byapplying both time variance and “elec-tronic 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-seattheatres (four microphones, twoprocessors, and 12 loudspeakers) tolarger 4,000-seat venues (eight micro-phones, four processors, and 96 loud-speakers). Its stated goals includeextending reverberation time, increas-ing sound pressure levels, improvingthe sound field in under-balcony areas,

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improving stage acoustics, andexchanging sound energy between thestage and audience area for uniformity.Like Lares, it is also intended for use inpractice rooms and other small per-formance spaces.An AFC system consists of at least

two AFC1 units, one of which is usedfor signal processing, and the other foroutput control. Each AFC1 has eightinput channels and 32 output channels;the system can be expanded to 96 out-put channels by cascading three AFC1units for output control and connectingthem to one AFC1 unit for signal pro-cessing. Systems with four processorsfacilitate zoning in larger venues.Microphones hung from the ceiling

at or around the critical distance wherereflected energy is equal to directenergy are used to pick up diffusedsound. Purpose-built loudspeakers areaimed horizontally or upwards, morethan the critical distance away fromthe audience area, in order to con-tribute to the diffuse field.

According to Yamaha, AFC hasbeen installed in more than 30 venues,mostly in Japan. Projects in the U.S.include an AFC-based renovation ofthe 3,485-seat Miller Auditorium atWestern Michigan University inKalamazoo, the 400-seat Church of St.Michael and St. George in St. Louis,Missouri, and the 800-seat Vestal HighSchool Auditorium in Vestal, New York.

Carmen“Carmen comprises a number of elec-tro-acoustic active cells (approximatelyfrom 16 to 40), each of them beingcomposed of a microphone, an elec-tronic filtering unit, a power amplifier,and a loudspeaker. Placed around thewalls and ceiling of the auditorium, thecells form virtual walls, depending onthe architecture and the acoustic prob-lem to solve. They only communicatebetween each other by the acousticway. The whole cells are controlled bya computer or an on-stage remotecontrol panel,” according to informa-

tion supplied by France’s CentreScientifique et Technique du Bâtiment(CSTB), which developed the system.“The innovative layout of the micro-

phones and loudspeakers producescompletely natural acoustics with aspace-time coherence of the soundfield preserved. Reverberation enhance-ment is simply coming from the mutualreflections between the different partsof the virtual walls, as for real walls in aroom. No microphone on stage isimpeding the normal use of the spaceabove the stage. Besides, the naturaldirectivity of the sound sources, andstage sound images cannot be altered,as when picking up the sound fromabove the head of the musicians orclose to stage and reproducing just asit 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’sclient list includes nine facilities inFrance and Monaco, with the excep-tion of the 1,900-seat Brighton Domein the U.K. That system, completed in2002, features 30 cells, including anactive orchestra ceiling reflector, and isprogrammed with presets for chambermusic, opera, and symphonic works.

System costsThe cost of installing an electronicacoustical enhancement system iswidely variable, with venue size beingapparently a much more significantfactor than the selection of any particu-lar system. From what I have been ableto gather, a complete system, includinginstallation, would rarely exceed the$1M dollar mark, and typically wouldbe less than half that. This representsan enormous cost saving over “equiva-lent” physical architecture renovation inthe case of remedial acoustical work.In the construction of new multipur-pose venues or smaller facilities inthese times of belt-tightening and costconstraints, it may also represent anoffer you can’t refuse.Next month, we’ll continue with a lookat how electronic acoustical enhance-ment systems have been received bymembers of the industry, performingarts, and general public.

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Ls a 0903 Electronic Acoustics

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