Operation Manual
CHAPTER 19. LIVE AUDIO EFFECT REFERENCE 243
operation after the signal falls below the threshold.
A slight amount of attack time (1050 ms) allows peaks to come through unprocessed,
which helps preserve dynamics by accentuating the initial portion of the signal. If these
peaks cause overloads, you can try shortening the attack time, but extremely short times
take the life out of the signal, and may lead to a slight buzziness caused by distortion.
Short release times can cause pumping as the compressor tries to gure out whether to
compress or not; while generally considered an undesirable effect, some engineers use it
on full drum kits to give unusual sucking effects. Careful adjustment of attack and release
times is essential when it comes to compression of rhythmical sources. If you are not used
to working with compressors, play a drum loop and spend some time adjusting Attack,
Release, Threshold and Gain. It can be very exciting!
A compressor can only react to an input signal once it occurs. Since it also needs to apply
an attack/release envelope, the compression is always a bit too late. A digital compressor
can solve this problem by simply delaying the input signal a little bit. Compressor offers
three different Lookahead times: zero ms, one ms and ten ms. The results may sound pretty
different depending on this setting.
Compressor can be used in three different EF (envelope follower) modes. With Peak se-
lected, Compressor reacts to short peaks within a signal. RMS mode causes Compressor
to be less sensitive to very short peaks and compress only when the incoming level has
exceeded the threshold for a slightly longer time. Opto mode results in a non-linear release
curve. Specically, the release behavior is faster initially, and slows down as the gain reduc-
tion approaches zero. So which type should you use? There's no right answer, of course,
but there are some common uses for each mode. Peak mode is more aggressive and pre-
cise, and so works well for limiting tasks where you need to ensure that there are absolutely
no signals over the set threshold. RMS is closer to how people actually perceive loudness
and is usually considered more musical. Opto mode, because of its non-linear release
time is often considered smooth and natural sounding. Opto compressors are commonly
used on vocals, bass and electric guitar. But as always, when it comes to compression, trust
your ears and not the meters!
In addition to the EF modes, Compressor offers three Model types that offer further options
for how the device measures and responds to signal levels. FF1 and FF2 are both feed-
forward models, which analyze the loudness of the incoming signal. These are the models
used in the former Compressor I and Compressor II devices, respectively. FB is a feedback