Preset Design; Notes On Preset Design - Lexicon 12T User Manual

Preset Design

Notes on Preset Design

PC-90 incorporates the results of a great deal of research into acoustics and reverberation.
Reverberation, or reflected sound energy, gives recorded music a sense of being performed in a
real acoustic location.
Using the Size and Spread Parameters
In the PC-90, the Size and Spread controls allow adjustment of the buildup and decay of the initial
part of the reverberation envelope. In the Chamber algorithm, Size acts as a master control for the
apparent size of the space being created by PC-90. Both Spread and Mid Rt vary linearly with the
setting of Size. Thus, maximum reverb time and spread may require high settings of Size. To find
an appropriate reverb sound, start with a preset with a similar sound to what you want to end up
with. Simply varying Size is often sufficient to arrive at the exact sound you are seeking.
Once a size has been selected, Spread and Shape are used to adjust the shape and duration of
the initial reverb envelope, which together provide the major sonic impression of room size. The
density is set by the size control, and the rate of decay is set by Mid Rt.
As Shape is raised to about 1/8 of its range, the initial sharp attack of the reverberation is reduced,
and reverberation builds more slowly. The envelope then sustains briefly before it begins to die
away at the rate set by Mid Rt. Spread has little or no effect on this shape.
When Shape is at 1/4 of its range, buildup is even slower and the sustain is longer. Now Spread
affects the length of both the buildup and sustain. As a rough estimate, the sustain will be
approximately the time value indicated by the Spread display (in milliseconds).
As Shape is raised further, the buildup and sustain remain similar, but now a secondary sustain
appears in the envelope, at a lower level than the first. This secondary plateau simulates a very
diffused reflection off the back wall of a hall, and is effective in creating a sense of size and space.
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