Lexicon CP-1 User Manual download pdf (Page 53)

Page 49

CP-1 Digital Audio Environment Processor

Theory

and

Design

sounds appear in the front left and right speakers (and the side left and right

speakers, if present).

The Rear Noise Chip parameter is preset to OFF, meaning that the high-

frequency sound in the rear channels is set solely by the Rear Rolloff

parameter. (The Rear Noise Chip should be ON for Dolby Surround

programs.) Rear Rolloff is preset to 14.1 kHz, its highest constant value. An

Automatic mode expands to accommodate signals steered to the rear, then

shuts down to 7 kHz for lower percussion leakage when there are no signals

there. This is a useful feature for films.

The Stereo Logic Program can provide an unusual and revealing way to

listen to music. With a multi-speaker surround system the program puts

you in the middle of the music, so that interior elements formerly buried in

the mix become audible. Try setting Front Effect and Rear Effect all the way

up; then mute the center channel by pushing System Mute to turn main and

effects signals off, then Effects Mute to turn everything but the center back

on. This allows you to hear all of the mix (except for strongly centered

material such as vocals) separated and spread throughout the room. This

method also provides an interesting look into the details of film sound

mixes.

The requirements for film sound are quite different from those for the

playback of music. The most important track in any film is the dialog. When

the two stereo channels are played back through two speakers with no

decoder, dialog will appear to come more or less from the center, but only

for those listeners on the center line of the main stereo pair.

The most important job for a Pro Logic decoder is canceling the dialog from

left and right loudspeakers. To be able to hear this you have to set up a center

speaker. We strongly recommend that a center channel speaker be used

with any surround decoder; the difference it can make to the subjective

quality of a film is enormous.

Assuming some form of center speaker has been provided, the next most

important point is providing enough spatial impression. Once again, the

best way to do this is with loudspeakers at the sides of the listeners. When

we tried this with the CP-1 we made an interesting discovery. When the Left

and Right loudspeakers are spread wide enough to fall within 20 degrees of

the listeners' sides, there is a tremendous change in the impact of the film.

The sound stage becomes much wider than the screen - so wide in fact that

the listener is literally drawn into the action. This effect should not be

surprising - lateral sound is known to grab our attention in a way that front

Speaker Set-Ups for Pro Logic

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Lexicon CP-1 User Manual Page 53

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