3Com CP-1 owner manual Theory, Design, Ambience Extraction, Ambience Generation

	Theory
	and
CP-1 Digital Audio Environment Processor	Design
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 programs 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	The confusing frontal reflections can
supplies a delayed and filtered L-R signal to rear speakers. On a good
	be absorbed leaving the essential lat-
recording this successfully recreates the original recording space, although
	eral ones. This is better, but not ideal.
the ideal listening area may be small.

The Surround programs, Stereo Logic and Pro 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 Pro Logic 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 programs 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 these programs the original stereo channels are pre- sented unaltered to the main loudspeakers, and new signals are generated 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 mode 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.

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.

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