Alesis 3630 Reference Manual page 15

In peak mode, this control sets how fast the limiter's internal circuitry reacts
to changes in input level. The longer the attack time, the more of a signal's
dynamics are "let through" before the limiting action kicks in. With slower
attack times, the limiter responds more to average signal level. This
produces a smoother sound that tends to retain dynamic character, but
the tradeoff is that the 3630 cannot react as rapidly to sudden level shifts.
Examples: Setting a longer attack time with guitar allows more of the pick
attack to come through. A longer attack time with kick drum lets through
more of the beater "thock." For recording, you may want to trade off
response time for smoothness. When used to prevent loudspeaker or
power amp clipping, a fast attack time is desirable.
Release (50 ms to 3 seconds)
This control works only with the Peak/RMS switch (section 1.5) in Peak
mode. RMS mode automatically adjusts the release time, depending on
the characteristics of the signals being processed.
In peak mode, this control determines how long it takes for the limiter to
return to unity gain after going into limiting. With short release times, the
limiter tracks every little change in level, producing a potentially uneven
or "rippling" effect that decreases dynamics but increases the average
output level. Longer release times tend to "squash" the signal more,
producing less overall output but retaining more of the signal's dynamics.
Excessive release times can be used as an effect. In the 60s using lots of
limiting with long release time on drums was a popular recording
technique.
Output (-20 to +20 dB)
The process of reducing dynamics lowers the signal's overall level. Use
this control to compensate by adding output gain.
Example: Limiting a signal by 6 dB will make the signal seem
approximately 6 dB softer. Compensate by using this control to increase
the level.
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