5.1 DigiRack Plug-Ins Guide - Digidesign Support Archives

Dynamics II
There are five types of DigiRack dynamics processors:
Compressor, Limiter, Gate, Expander/Gate
and De-esser.
Compressor II
The Compressor reduces the dynamic range of
signals that exceed a selected threshold by a specific
amount. The increase of input signal
needed to cause a 1dB increase in the output signal
of the compressor is called the compression
ratio. With a ratio of 4:1, for example, an 8dB increase
of input produces a 2dB increase in the
output.
Audio material often varies in loudness, and can
be above the threshold at one moment and below
it the next. The Attack slider sets the compressor’s
response time, or attack. The Release
slider sets the amount of time that it takes for
the compressor’s gain to return to its original
level.
Using Compression Effectively
To use compression most effectively, the attack
time should be set so that signals exceed the
threshold level long enough to cause an increase
in the average level. This helps ensure that gain
reduction doesn’t decrease the overall volume.
Release times should be set long enough that if
signal levels repeatedly rise above the threshold,
they cause gain reduction only once. If the release
time is too long, a loud section of the audio
material could cause gain reduction that persists
through a soft section. Of course, compression
has many creative uses that break these rules.
The Compressor has built-in metering that allows
you to monitor the amount of gain reduction
taking place. The gain reduction meter usually
remains at 0 level when the input signal is
below the threshold and falls to the left to show
the amount of gain reduction in decibels when
the input signal exceeds the threshold.
Compressor II plug-in Compressor settings created in version 5.x
and later of Pro Tools are not compatible
with earlier versions. Saving a session in a
pre- 5.x format will cause Compressor settings
to be lost.
Compressor Parameters:
Phase Invert Inverts the phase (polarity) of the
input signal, allowing you to change frequency
response characteristics between multi-miked
sources or to correct for miswired microphone
cables.
Phase Invert
Gain Provides overall output gain adjustment. It
allows you to compensate for heavily compressed
signals.
Chapter 4: DigiRack Real-Time TDM and RTAS Plug-Ins 27