Lexicon CP-1 User Manual download pdf (Page 43)

Page 39

CP-1 Digital Audio Environment Processor

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 pro-

grammed delay. Although the CP-1 provides adjustments to compensate

for off-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.

quency.

Lexicon’s implementation, called the Panorama program, 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

Theory

and

Design

L R

Input

Signal

Speaker

Level

Higher order

Correction

First order

Speaker

Level

Higher order

L R

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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Lexicon CP-1 User Manual Page 43

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