3Com CP-1 owner manual Ambience Program

Theory

and

Design

CP-1 Digital Audio Environment Processor

Panorama greatly increases low frequency width and should only be used with true binaural recordings, which have very little out-of-phase low frequency energy. A few compatible binaural recordings are becoming available, in which the low frequency width has been increased to match the requirements of loudspeaker playback. These recordings may sound best when played with the Normal setting.

Panorama is capable of simulating side loudspeakers effectively, but cannot mimic sound sources to the rear of the listener. So we have added a simple delayed Left minus Right signal which can be sent to rear loudspeakers. The delay is adjustable, as is the treble rolloff.

For a listener in the ideal position, Panorama, with one or two rear speakers, gives a nearly ideal re-creation of the original recording area.

Panorama is also used as an element in the Ambience and Reverberation programs, where it can synthesize side loudspeakers which are not present in the installation. In this mode the stereo inputs to the CP-1 are fed directly to the front loudspeakers, with the digital outputs of the CP-1 mixed in according to the setting of the Effect Level control. The Ambience or Reverb side outputs are sent through Panorama before being mixed into the front loudspeakers, so the added sound spreads beyond them and does not interfere with the original material. When side speakers are present, the Panorama Effect parameter is automatically turned down and no mixing occurs into the front speakers.

Speaker alignment is important. A 6" difference in the distance to the rear wall can greatly change the ef- fective area, unless compensated for by the LISTENER POS parameter.

The Ambience

Program

While the Panorama program recreates the space that already exists in the recording, the Ambience program actually generates the side and rear reflection patterns of a number of ideal concert halls. The reflections were determined by computer ray-tracing using architectural data, augmented by Lexicon’s 15 years of experience with digital concert-hall simulation.

The Ambience simulation is done in stereo. Instead of feeding combined left and right channels to the processor, the CP-1 has two input points corre- sponding to instruments placed on the left or right side of the stage. From these the computer calculates the loudness and delay of the reflections for the side and rear loudspeakers.

Ambience generates primarily the strong reflections which appear early in the reverberation process (in the first few hundred milliseconds). Although some reverberant decay can be added with the Liveness parameter, the early reflections constitute the primary audible effect, giving you the impression of the hall surrounding you while the music is playing. As in actual concert halls, the most important contribution to spatial realism will

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