Lexicon CP-3 Plus Supplementary Manual page 10

CP-3 PLUS Digital Surround Processor
Lexicon's implementation, called the Panorama mode, was designed using
measured data on sound diffraction around the head to shape the frequency
spectrum of the canceling signal. This signal is then itself canceled by a
second signal, and so on, so that both the crosstalk and the signal that is
canceling it are eliminated.
This works extremely well when the room is well damped and the listener's
head is correctly positioned. The first order devices described earlier
required the listener to sit on the center line between the loudspeakers, and
to arrange the angle between the speakers to correspond to the modemed
delay. Although the CP-3
center listening and for varying speaker angles, maintaining a consistent
listening position is still important and becomes more so with increasing
frequency. With wide speaker angles, a movement of as little as 1 inch can
make a perceptible difference. Fortunately, the effect is usually fairly good
everywhere within a zone about one foot wide.
To achieve the fullest Panorama effect, your main loudspeakers should
have good imaging. The smaller speakers that tend to be used with video
systems may have an inherent advantage here but the most important
requirement is that the two speakers have identical frequency response and
symmetrical dispersion. It is not necessary, or desirable, to turn your
listening room into an anechoic chamber but moving the speakers away
from the walls can be helpful, as can adding absorption (as provided by
carpets, curtains and/or sound-absorbent panels) to reduce the reflectivity
of the floor, walls and ceiling.
PLUS provides adjustments to compensate for off-
PLUS
CP-3 Theory
and Design
First-order correction travels to left ear,
where it will be heard unless canceled by
an additional correction. When these
higher-order corrections are supplied,
accurate cancellation is possible.
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