Lexicon CP-3 Plus Supplementary Manual page 12

PLUS
CP-3 Digital Surround 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 delayed
Left minus Right signal which can be sent to the side and rear loudspeakers.
The delay is adjustable, as is the treble rolloff.
For a listener in the ideal position, Panorama, with surround (side or 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
modes, where it can synthesize side loudspeakers which are not present in
the installation. In this mode the stereo inputs to the CP-3
to the front loudspeakers, with the digital outputs of the CP-3
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.
While the Panorama mode re-creates the space that already exists in the
recording, the Ambience mode actually generates the side and rear reflec-
tion patterns of a number of ideal concert halls. The reflections were
determined by computer ray-tracing using architectural data, augmented
by Lexicon's decades of experience with digital concert-hall simulation.
The Ambience simulation is done in stereo. Instead of feeding a monaural
signal derived from the combined left and right channel inputs of the
processor, the CP-3 PLUS has two input points corresponding 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. By using full stereo for the inputs to the simulation programs,
the spread or separation of the soundstage is automatically preserved in the
simulation process. This obviates the need for adjustment on every different
recording, a chore required for decent results on some other systems.
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 im-
Speaker alignment is important. A 6"
difference in the distance to the rear wall
can greatly change the effective area,
are fed directly
PLUS
unless compensated for by the LIS-
PLUS mixed in TENER POS parameter.
The Ambience
Mode
PLUS
CP-3 Theory
and Design
9