Birmingham ElectroAcoustic Sound Theatre

Birmingham ElectroAcoustic Sound Theatre, or as it is more commonly known, BEAST, is a sound diffusion system specifically designed for the performance of electroacoustic music. It is a long-running project of the Electroacoustic Music Studios at the University of Birmingham. BEAST consists of up to over 100 channels of loudspeakers arranged in pairs, or more recently to allow the diffusion of octaphonic works, circles of eight, and includes ultra-low frequency loudspeakers ('bass bins') and custom-built trees of high frequency speakers ('tweeter trees') that can be suspended above an audience.

The minimum set-up that BEAST would ordinarily use for stereo diffusion comprises a set of loudspeakers which Professor Jonty Harrison (of the University of Birmingham) terms the Main Eight. These four pairs of loudspeakers, using BEAST nomenclature, are termed Main,Wide,Distant and Rear. The Main and the Wide speakers together form the main, frontal sound image, the Main speakers being placed to act somewhat like the loudspeakers in a typical studio, and the Wide speakers acting to stretch that sound image out across the audience's sound stage. The Rear speakers, which are behind the audience, provide immersion and the possibility of movement around the audience. Finally the Distant speakers, which are positioned to hold their image behind the Main speakers, create a sound whose perspective is distant to that of the Main pair. Other speakers are added to this Main Eight to allow additional possibilities for sound movement and differing sound perspectives.

BEAST is a dynamic system: during a performance the performer operates a custom-built console, called the diffusion desk, with which he can individually and dynamically control the level of each loudspeaker, or groups of loudspeakers. This enables him or her to actively articulate the piece's implied spatial sound detail within the real space of the performance venue, in order to realise and interpret the composer's intentions. The system also includes equipment for the live processing of sounds so that, for instance, the sounds of a live violinist can be processed and incorporated into the soundstage.

The BEAST diffusion console has developed significantly over the years. The earliest systems depended on those commercially available mixing desks which had direct outputs from each fader. The stereo input signal from, for example, a tape-machine was split passively into the input channels on the desk, alternating left and right. The direct output from each channel fed the amplifiers for the loudspeakers, thus giving the individual control of each loudspeaker required for diffusion. The main disadvantage of this system was that it offered very little flexibility, making it difficult to move between sources in different formats (for example, quadraphonic, octaphonic or pieces with live input). In some situations complicated rewiring would required which could be prone to errors, particularly during a performance.

The first custom built console BEAST developed was still based on a commercially available mixing desk, but which had been extensively modified, adding a matrix input section and balanced outputs. The matrix input section allowed a number of inputs to be assigned to any fader input using a series of push buttons. Where multiple sources where used during a concert, this allowed each work to have their assignment preset on the matrix. BEAST's experiences with this experimental desk led to them to design their last analogue desk, still in use, called the 3D. This was a fully custom built console with an extensive matrix input which was very easy and flexible to use.

With the electroacoustic community's renewed interest in multichannel formats, and in particular octaphonic set-ups, came the need for BEAST to address how such pieces should be diffused. The diffusion of multichannel formats was too complex a task for the standard BEAST console, and BEAST turned to software solutions to solve these problems: first MAX/MSP and most recently, Supercollider. Now, rather than using an analogue desk, a digital multichannel sound interface is used, and controlled via specially written applications using MIDI faders. This offers the maximum flexibility, with one fader, for example, being able to control only one loudspeaker, a stereo pair or an octaphonic circle depending on how the system has been configured. Using this system, multiple octaphonic groups, placed in different positions around the audience, can be used to diffuse octaphonic source material in a manner similar to that used for stereo. In this case, each fader controls one octaphonic group.

Since its debut in December 1982, the system has performed in over 140 concerts in the UK and Europe, both alone and with musicians from all over the world. BEAST has appeared at many festivals and concerts, including the Edinburgh International Festival and Huddersfield Contemporary Music Festival, Multimedia 2 in Karlsruhe, in the Purcell Room, The Royal Dutch Conservatory in Den Haag, the Adrian Boult Hall in Birmingham and the Henry Wood Hall in Glasgow. It was acclaimed when used as the concert sound system at the 1990 International Computer Music Conference held in Glasgow, and at the Aspekte Festival in Salzburg.

See also

• Acousmonium
• Surround sound

References

• The Electroacoustic Music Studios at the University of Birmingham. Retrieved on 22 April 2007.