Specifications

Chapter 5: DigiRack Real-Time TDM and RTAS Plug-Ins 41
tively low, high frequencies decay more quickly
than low frequencies, simulating the effect of air
absorption in a hall. The maximum value of this
control is Off (which effectively means bypass).
Low-Pass Filter
Low-Pass Filter controls the overall high fre-
quency content of the reverb by setting the fre-
quency above which a 6 dB per octave filter at-
tenuates the processed signal. The maximum
value of this control is Off (which effectively
means bypass).
Dynamics II
There are five types of DigiRack Dynamics pro-
cessors: Compressor, Limiter, Gate, Ex-
pander/Gate and DeEsser.
Compressor II
The Compressor reduces the dynamic range of
signals that exceed a selected threshold by a spe-
cific amount. The increase of input signal
needed to cause a 1 dB increase in the output
signal of the compressor is called the compres-
sion ratio. For example, with a ratio of 4:1, an
8 dB increase of input produces a 2 dB increase
in the output.
Audio material often varies in loudness, and can
be above the threshold at one moment and be-
low it the next. The Attack slider sets the com-
pressor’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 re-
lease 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
shows 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 set-
tings to be lost.