Alesis S4 Plus Reference Manual page 100

Editing Effects: Chapter 7
Gated. Gated Reverb is a very popular effect on drums first found on English records
in the early 1980s. This reverb type can simulate applying a noise gate (a device that
automatically decreases the volume once the signal falls below a certain level) across
the output of the reverb thereby causing the initial attack of the reverb to sound very
big, but the tail of the reverb to be cut off very quickly. Although this effect is not
found in nature, it works great for modern drums, percussion, and any quickly
repeated, transient source.
Reverse. The Reverse Reverb type is an inverted reverb in which the volume
envelope is reversed. This means that the signal begins softly but grows louder until it
is cut off, rather than loud to soft as normal.
Pre-Delay Time
Pre-Delay is the slight delaying of the Reverb itself so that the dry signal more easily
stands out from the Reverb. A bit of Pre-Delay can sometimes make certain
instruments (such as snare drums) sound bigger. Use Quad Knob [2] to adjust the
Pre-Delay Time in 10ms intervals, and/or use Quad Knob [3] to adjust the Pre-Delay
Time in 1ms intervals. This Pre-Delay is part of the Reverb itself; don't confuse it with
the separate Delay modules available under the Delay function.
Pre-Delay Mix
Quad Knob [4] allows you to mix the amount of Pre-Delay into the Reverb signal
path. This gives you the ability to hear a bit of the Reverb before the loudest part of
the Reverb (the Pre-Delayed Reverb) sounds. This makes for bigger and smoother
sounding Reverb settings.
Reverb (Page 3)
Input Filter
This is a low-pass filter which comes before the Reverb input. Use Quad Knob [1] to
adjust the filter frequency. Lower the Input Filter to remove high frequencies from the
input signal before they go into the Reverb.
Decay
The Reverb Decay determines how long the Reverb will sound before it dies away.
When using the Reverse Reverb type, Reverb Decay controls the Reverse Time.
Low Decay and High Decay
These two parameters allow the Decay Time to be set separately for both the low and
high frequencies of the Reverb. This means that you have control over the tonal
shape of the Reverb itself, being able to make the high frequencies die faster if the
effect is too bright, and being able to make the lows die faster if the effect is too
boomy. This allows you to simulate different surfaces of a room or hall, with softer
surfaces absorbing more high frequencies and smaller rooms having faster low
frequency decay.
If the selected Reverb type is Gate, the Low Decay parameter is unavailable.
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