Lexicon CP-1 PLUS V2.0 Owner's Manual page 48

CP-1 Digital Audio Environment Processor
sides. Both methods depend on having the added sound come from a
different direction than the original music, and each method has some
advantages. With either method of generating SI there is an additional
choice the CP-1 allows the user to make: the sideways energy cues of the
original recording can be extracted by the CP-1, or a different hall sound can
be generated and supplied from the correct directions.
Ambience Extraction
The Panorama and Surround modes in the CP-1 extract the original acoustic
cues from the recording and present them to the listener from the correct
directions. We call this ambience extraction. The three Panorama programs
can even do this with only two loudspeakers. Panorama uses crosstalk
elimination to fool the ear into thinking there is a continuous band of
loudspeakers extending all the way to the sides of the listener and also
supplies a delayed and filtered L-R signal to rear speakers. On a good
recording this successfully recreates the original recording space, although
the ideal listening area may be small.
The Surround mode variations, Stereo Logic, Pro logic, TV Matrix and
Music Logic, also work by ambience extraction. They divide the front
energy among three or more loudspeakers and supply a delayed and
filtered difference signal to rear loudspeakers. Because a center speaker is
provided, the left and right speakers can be placed far enough to the sides
of the listener to directly excite significant SI and the resulting image is wide
but seamless. This set-up can sound similar to Panorama, and it works over
a large listening area.
Stereo Logic and TV Matrix also provide steering. Steering works by
enhancing the directionality of the loudest sound in a mix; it steers the
sound out of loudspeakers where it is not needed and into the ones closest
to its direction in the image. In popular music the loudest sound is usually
the vocals, which will be preferentially steered toward the center loud-
speaker. Some steering is frequently beneficial to music recordings played
with a surround speaker arrangement, and it is essential for films.
Ambience Generation
The Reverb and Ambience effects in the CP-1 synthesize the side and rear
sound of several different acoustic spaces. Rather than extracting the
acoustic cues of the original hall from the recording, they generate a new
environment, effectively enlarging and improving the acoustics of your
listening room. In the Concert Hall mode the original stereo channels are
presented unaltered to the main loudspeakers, and new signals are gener-
ated for the side and rear loudspeakers. Both Ambience and Reverb can be
configured to use a version of Panorama to generate the correct side sound
even when side loudspeakers are absent. In this configuration, the side signals
are first passed through Panorama before being mixed into the main
loudspeakers, so the resulting hall sound is perceived as coming from the
side and is well separated from the original sound.
Theory
Design
The confusing frontal reflections can
be absorbed leaving the essential lat-
eral ones. This is better, but not ideal.
With the CP-1, confusing short re-
flections can be absorbed; the CP-1
will supply the essential lateral
sound - which can simulate a much
larger space.The more absorbent the
playback room, the better it will
sound, and the closer it will sound to
a real hall, or larger environment.
and
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