Lexicon PCM 80 - Manual (Page 93)

3-35
The Algorithms and Their Parameters
Shape, Spread
In the Chamber and Infinite algorithms, Shape and Spread work together to
control the overall ambience of the reverberation created by the PCM 80. Shape
determines the contour of the reverberation envelope. With Shape all the way
down, reverberation builds explosively, and decays quickly. As Shape is
advanced, reverberation builds up more slowly and sustains for the time set by
Spread. With Shape in the middle, the build-up and sustain of the reverberation
envelope emulates a large concert hall (assuming that Spread is at least halfway
up, and that Size is suitably large — 30 meters or larger). Low Spread settings
result in a rapid onset of reverberation at the beginning of the envelope, with little
or no sustain. Higher settings spread out both the buildup and sustain. In the
Inverse algorithm, Spread is fixed, and only a Shape control is available.
Def
Available in the Concert Hall and Glide>Hall algorithms, Definition affects the
echo density buildup rate during the latter part of the decay period. At 0, the rate
is determined by the program material. Raising Definition causes the sound to
become choppier — the decrease in density of the echoes creates increasingly
distinct, repetitive echo trails.
Depth
Available in the Concert Hall and Glide>Hall algorithms, this control sets the
output amplitude envelope, changing the listener's perspective from the front to
the rear of the hall.
Spin
Spin affects the movement of the reverberation tail. The object of Spin is to
continuously alter the timbre of the reverberant sound. This makes the result
more natural, without making the position of instruments unstable. Spin should
typically be set to values between 10 and 50. Higher values may make the timbre
of piano or guitar unstable.
Chorus
In the Concert Hall and the Glide>Hall algorithms Chorus randomizes delay
times and introduces modulation to make reverberation sound less metallic.
Increasing Chorus increases the rate of modulation. Because Chorusing can
cause pitch variation, this parameter should be set with care when using sources
with very little pitch wobble (such as guitar or piano). A good practice is to
increase the setting until pitch wobble becomes noticeable, then lower it slightly.
Link
This control is available in all algorithms except Inverse. When Link is set to On,
the reverb time (Mid Rt) and Spread scale linearly as the Size control is varied.
For some special effects, Mid Rt, Spread and Size can be unlinked.
Rvb Width
In all of the 4-Voice algorithms, this control performs the same function as FX
Width, but controls the audio of only the reverb and post delay reverb.
Rvb In/Out
Rvb In and Rvb Out control the level of the audio going into and coming out of
the reverb effect. Rvb In has a range of Full (0dB) down to -85dB, and Off. Rvb
Out has a range of Full (0dB) down to -24dB, and Off. Rvb Out does not affect
the level of the pre-echoes set by the Ref Lvl and Eko Fbk parameters.
Rvb Design cont'd.