The concept of controlling acoustic conditions with electro-acoustic augmentation is nearly as old as the development of electronic sound production. Early examples in the US include experiments by Edison, as well as, Bell Laboratories in the 1930’s. Advancements in electronic communication equipment developed during WWII paved the way for improved fidelity in audio systems for film, and the advent of the modern recording industry. The first commercial electro-acoustic “Reverberation” systems were developed using tools and components available during the early 1960’s. This imposed substantial limitations - both with respect to system integration as well as what could be achieved sonically. Electronic components used in these systems incorporated tubes or early transistors. Equalization did not exist, and the only means of signal delay involved either acoustical paths or mechanical means using tape loops and multiple playback heads.
Figure 1. Early multi-head tape delay system
In the late 1960’s, a new development would usher in a paradigm shift that would have profound affects on virtually every aspect of music reproduction An MIT professor and medical doctor named Francis Lee was experimenting with digitizing the waveform of a human heat beat on an oscilloscope so that it could be delayed and viewed again. Barry Blesser, then a teaching assistant to Dr. Lee, suggested putting audio through the system, and the result was a 100ms delay – accomplished entirely in the digital domain. Dr. Lee together with engineer Chuck Bagnaschi, formed American Data Sciences to undertake development. The company changed its name to Lexicon and produced the Delta T101 - the world’s first commercial digital audio product. While a 100ms delay time and 12bit audio is not impressive by today’s standards, the Delta T allowed engineers to accomplish tasks that were considered nearly impossible at the time. This, however, was merely a prelude to the next paradigm shift. In 1978, Dr David Griesinger developed the first commercially viable digital reverb system which became the legendary Lexicon 224. This system and its successor, the Lexicon 480L, became (and remains) the gold standard for audio production throughout the world. While working as Advanced Products Manager at Lexicon supporting this system, Steve Barbar received an inquiry from a friend and colleague, Mr. Neil Muncy. Mr. Muncy was working with the Ontario Heritage Foundation on the restoration of a unique vaudeville theatre in Toronto. The venue (the Elgin and Wintergarden Theatres) was one of the last remaining “double-decker” theatres in existence (a complex with one theatre built on top of another theatre). The architecture was to be painstakingly restored as original. The challenge that Mr. Muncy presented involved the need for acoustical conditions that would enable the venue to accommodate a wide range of performances. Electro-acoustic enhancement afforded a solution that would allow for authentic architectural restoration, however, the systems available at that time were deemed to be both overly complex, and lacking sufficient sonic quality
Dr. Giesinger’s extensive published scientific research in room acoustics, and music reproduction; combined with experience in producing world class digital reverberation, made him an ideal candidate to investigate the performance criteria of electro-acoustic enhancement systems. Thus, a research project was formed with Dr. Griesinger investigating the physics required to make a substantial improvement in the state of the art, while Muncy and Barbar investigated the requirements for transducers and system integration, with some assistance from Canada’s National Research Council.
Dr. Griesinger quickly discovered the underlying cause of both system complexity as well as poor performance in early systems – acoustic feedback. This occurs when the sound generated by the loudspeakers is picked up by microphones and is recirculated in a loop through the system; resulting in coloration or oscillation (howling). In order to avoid coloration, early systems required large numbers of independent microphone and loudspeaker “channels”. Each channel was separated by the critical distance of the volume (the point at which the level of the reverberation and direct energy have equal magnitude). In addition, each channel must be carefully placed to minimize interaction with any other channel. The gain of each channel must be reduced sufficiently to maintain stable operation. Thus, the architecture of such systems demands a high level of complexity, and imposes substantial limitations on system integration.
The technological breakthrough that Dr. Griesinger devised (and patented) utilizes advanced digital signal processing to decorrelate loudspeaker and microphone signals in real time, thus providing a substantial increase in system gain without coloration. This eliminates the need for the large number of independent microphone and loudspeaker channels, which dramatically simplifies system architecture. Dr. Griesinger then created a new acoustics algorithm specifically for electro acoustic enhancement that utilized this new processing.
Signal processors using Dr, Griesinger’s algorithm were integrated into the system designed by Muncy and Barbar, and installed in the Elgin Theatre in 1989. At the time of the installation, a lighting truss that was not included in the original theatre design obstructed the microphone placements for the system. This necessitated moving the microphones to the balcony rail – nearly 50 feet from their intended position. However, the system processing provided ample feedback suppression to enable both optimum acoustical conditions, and remain free from coloration.
This process became known as LARES (Lexicon Acoustic Reinforcement and Enhancement System). In 1990 LARES made its official debut at the Audio Engineering Society conference in New York, and was nominated for a TEC award. The conference was held in the New York Hilton, and a small system installed in one of the “demonstration” hotel rooms. Each day, a line to hear the 10 minute demonstration formed from one end of the hallway to the other and wrapped back to the elevators. Representatives from Wenger Corporation heard the demonstration and enquired about using the technology in their sound isolating practice rooms. Dr. Griesinger created a simplified algorithm that could operate using Lexicon’s consumer products. Together with Russ Berger, Barbar engineered a system that Wenger marketed as V-Room. In 1995, LARES Associates was formed as an independent company that provided turnkey acoustic enhancement systems with LARES branded products. In addition to the core signal processing, this included LARES branded amplification, and a range of loudspeakers specifically designed for acoustic enhancement.
LARES Associates developed two generations of LARES branded systems. The second generation incorporated advancements in digital audio processing and communication which produced the first all digital acoustic enhancement system. During this time, Lexicon had been purchased by Harman Inc., and moved in name only to another Harman division of located in Salt Lake City. The digital reverberation systems that once elevated the brand were discontinued. Fortunately, the ongoing growth of the internet fueled the development of faster and more powerful processing designed for long life cycles and constant use. It had numerous advantages, but the greatest was the ability to update hardware without having to re-engineer system software.
Another significant paradigm shift was also taking place. Dr. Griesinger had been conducting ongoing research in human auditory perception for some time, As a result of several experiments conducted with Barbar, it became apparent that a new approach to algorithms for electro-acoustic enhancement was warranted. This culminated in the development of the third generation of hardware and software –which would be branded as E-Coustic Systems to both distinguish it from LARES branded products, and enable us to provide a range of hardware options tailored for specific markets.
Our first development was dual purpose. We needed hardware that could replace the largest systems already in use. These systems serviced 50,000 seat areas and had over one hundred - if not hundreds - of independent outputs. In addition, we wanted software both that incorporated our new ideas, and provided substantially improved sonic performance. Unlike previous developments for our smallest systems that required compromises to both hardware and software, we wanted the smallest systems to have sonic performance that matched our largest systems.
E-Coustic Systems Generation 3 has achieved these goals. The software that runs in all of our systems is now identical. Our largest systems based on the E-Architecture Matrix processor supports over 1000 channels – nearly three times the capacity of its predecessor. The E-Performance systems scales this by half making it ideal for venues with seating capacity from one hundred to three thousand seats. It also provides a substantial cost savings when compared to the previous second generation systems. We have successfully demonstrated the E-Venue system at prominent industry trade shows and exhibits on a card table, making it the smallest system of its kind in the world. This, however, is only the beginning. We are developing new lower cost platforms for applications that previously could not afford this technology.
Our research in fields relating to human perception is ongoing. This will continue to benefit the audio industry as a whole, and in addition, further the state of the art in electronic architecture.