Reference Manual
CHAPTER 21. LIVE AUDIO EFFECT REFERENCE 290
high ratios, this so-called hard knee behavior can sound harsh. With higher (or soft)
knee values, the compressor begins compressing gradually as the threshold is approached.
For example, with a 10 dB knee and a -20 dB threshold, subtle compression will begin at
-30 dB and increase so that signals at -10 dB will be fully compressed.
The easiest way to visualize Compressor's behavior is by observing how the graph changes
when you adjust the threshold, ratio, and knee values. Input level is measured on the
horizontal axis, while output level is represented vertically. Next to the graph is the Gain
Reduction meter, which shows how much the gain is being reduced at any given moment.
The more reduction, the more audible the effect; a gain reduction above 6 dB or so might
produce the desired loudness, but signicantly alters the sound and is easily capable of
destroying its dynamic structure. This is something that cannot be undone in later production
steps. Keep this in mind especially when using a compressor, limiter or sound loudness-
maximizing tool in the master channel. Less is often more here.
Because compression reduces the volume of loud signals and opens up headroom, you can
use the Output slider so that the peaks once again hit the maximum available headroom.
The Output meter shows the output signal's level. Enabling the Makeup button below the
Output slider automatically compensates the output level if the threshold and ratio settings
change.
The Attack and Release controls are essential parameters for controlling the response time
of Compressor by dening how fast it reacts to input-level changes.
Attack denes how long it takes to reach maximum compression once a signal exceeds
the threshold, while Release sets how long it takes for the compressor to return to normal
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!