3Com CP-1 Two-Way Radio User Manual

Page 41
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.
The Ambience
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.
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