3Com CP-1 owner manual Be the sound that comes from the sides

Theory and Design

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be the sound that comes from the sides.

The best way to generate spatial im- pression (SI) is with appropriate sig- nals from loudspeakers at the side. Reverb, Ambience and the Surround programs can all be used to generate these signals.

A

B

Placement of side loudspeakers is critical! Placement B sounds much better than A, especially when the room is well damped.

Early research with quadraphonics involved extensive experimentation with speaker placement, and confirmed that additional speakers beside the listener sounded better than the conventional approach of putting pairs of speakers in front and behind. Our research into speaker placement with Ambience confirmed the previous results of others: The side speakers should be directly to the side of the main listening position, plus or minus about 20 degrees. Beyond this critical angle the spatial impression is greatly reduced.

The sides are the most important additional speakers, much more so than the rears. Keep in mind that, although you can use the left and right main speakers to simulate a phantom center speaker, you cannot produce SI with one speaker in the front and one at the rear . (You can perform this experiment for yourself with the CP-1 using the Ambience program: Try the side speakers both in their usual positions and in the front corners. If your listening room has enough absorption to damp its side-wall reflections, the side location will provide much more spatial impression, and will sound substantially better.) Speakers in the front are useful - if you want the best possible sound from Ambience you may want to try an additional pair in the front corners, wired in parallel with the rear. This additional pair, as well as the rear speakers, may sound best if placed above the listener.

The effectiveness of the CP-1’s Ambience simulation is heavily dependent on the source material and the playback room. If the playback room is large and reverberant, its reflections may dominate those generated by the program. Carpet, drapes and furniture can all be used to break up or absorb undesirable reflections, making it easier to hear the processor’s output. The balance between the side, rear and front speakers is also very important. If the channels are set up properly, no single speaker will be audible by itself.

There are two basic hall shapes in Ambience: Rectangular and Fan. In a listening room with sufficient acoustical absorption, using source material without too much reverberation of its own, the two shapes are clearly distinguishable. For most classical recordings the rectangular hall sounds somewhat better because of its stronger side reflections. In our fan-shaped hall (unlike actual physical designs) you can increase the proportion of side to rear sounds, by increasing the Effect Level and shifting the F/B Balance controls toward the front. When this is done, another different but also pleasant sound results.

Although the Ambience program can provide some recirculation (adjust- able with the Liveness parameter), for long decay times it is better to use Reverb. The Large Hall ambiences are not intended to be used on material which is more appropriate to a smaller ambience, such as a small hall or a club. Highly percussive material is almost always better in the Small program which is quite successful in livening and expanding popular

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