Lexicon CP-3 Plus Supplementary Manual page 26

PLUS
CP-3 Theory
and Design
PLUS
CP-3 Digital Surround Processor
Re-Equalization is provided as a control to compensate for the fact that the
soundtracks in films sound "bright" when listened to in a home environ-
ment. This results from a combination of the way we perceive sound in large
halls vs. small rooms, and the theater equalization which has become
standardized throughout the movie industry. The re-equalization control
restores the sound to its natural balance, and reduces listening fatigue
dramatically by reducing excessive high frequencies.
As the surround channel in a Dolby stereo film is monaural, the signal is
neither spacious nor enveloping. In a theater, the quantity and placement of
surround speakers compensates for this; in the home, arrays of 12-18
speakers are generally impractical. To diffuse the perceived sound, the
CP-3 PLUS (in the decorrelated mode) provides a decorrelation algorithm
which, after the monaural signal is split in two, alters the phase/time
relationships between channels slightly. This eliminates the mono effect
from the rear channel and creates an enveloping soundfield. When the
"Stereo Surround" parameter is selected, the rear channels become stereo-
phonic, and the decorrelation is unnecessary. This setting is recommended.
Timbre matching compensates for the difference in characteristics of
sounds coming from different locations. In real life, timbre differences help
us differentiate sounds which originate from the sides and rear from those
originating from the front . In a film, however, when sound is panned from
front to rear, or from rear to front, these changes, which are present even
with perfectly matched speakers, are undesireable. Timbre-Matching pro-
vides equalization to the surround channels, reducing the perceived change
in character of sounds which are panned from the screen into the surrounds.
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