IH> I just recently purchased an Alesis 3630 compressor for my
IH> system. However, I haven't worked with compressors before,
IH> and I was hoping someone might be able to tutor me in their use.
Just a quick few notes for you - hope they help!
"Dynamic range" is the difference between the softest sound
possible and the loudest sound possible in an audio device, be
it a recorder, a mixer, etc.  "Compression" is used to reduce
the dynamic range of an audio signal.  It is most effective for
matching the signal being processed with the equipment's ability
to capture dynamic range.  To compress the human voice from a
microphone source and record it to reel-to-reel efficiently
("pack the tape"), you need to reduce the dynamic range to around
80dB.  For cassettes, it's lower of course, since they can't
capture the same range that open reel tape can.
There are several elements of control on most compressors...two
that are most common are RATIO and THRESHOLD.  The RATIO
controls how many decibels (dB) go into the unit, versus how
many come out.  The THRESHOLD control determines the level at
which audio processing takes place.
Compression ratios of between 1.1:1 (1.1dB in to 1 dB out) up to
about 5:1 are considered to be "compression".  Ratios of about
7:1 - 20:1 or infinity are considered to be "limiting".
Side effects of compression include the loss of high and low
frequencies, and a "louder" sound at the same gain level.
Try setting an overall voice/music mix at 7.5:1 ratio, at -10 or
-20dB threshold and see how you like the sound.  It gives a lot
of compression with gentle limiting, assuming you're working
with a hybrid compressor/limiter.
Mark Shander, Moderator
PRO_AUDIO
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