Dynamics Processors
380
Appendix
Compander
A compander is a compressor-expander—a combination of signal compression
and expansion. The compander attenuates the input signal above the threshold
as well as the level below the width. For very dynamic material, this program
allows you to retain the dynamic range without having to be concerned with
excessive output signal levels and clipping.
CompanderH (CPH) and CompanderS (CPS) parameters:
Threshold determines the level of input signal required to trigger the com-
pander. Signals above the threshold pass through unaffected. Signals at and
below the threshold level are attenuated by the amount specified using the
Ratio parameter. The trigger signal is determined using the KEY IN parameter.
Ratio controls the amount of companding—the change in output signal level
relative to change in input signal level. With a 2:1 ratio, for example, a 10 dB
change in input level (above the threshold) results in a 5 dB change in output
level. The hard compander (CPH) has a fixed ratio of 5:1 for expansion and the
soft compander (CPS) has a fixed ratio of 1.5:1 for expansion.
Attack controls how soon the signal is companded once the compander has
been triggered. With a fast attack time, the signal is companded almost immedi-
ately. With a slow attack time, the initial transient of a sound passes through
unaffected.
Out Gain sets the compander’s output signal level.
Width is used to determine the distance, in decibels, between the expander and
the compressor. With a width of 90 dB, the expander is effectively switched off
and the compander is simply a compressor-limiter. With a smaller width (30dB)
and a high threshold (0dB), the compander is an expander-compressor-limiter.
Release determines how soon the compander returns to its normal gain once
the trigger signal level drops below the threshold.
Parameter
Value
Threshold (dB)
–54 to 0
(55 points)
Ratio
1.0, 1.1, 1.3, 1.5, 1.7, 2.0, 2.5, 3.0, 3.5, 4.0, 5.0, 6.0, 8.0,
10, 20
(15 points)
Attack (ms)
0 to 120
(121 points)
Outgain (dB)
–18 to 0
(36 points)
Width (dB)
1 to 90
(90 points)
Release (ms)
5 ms to 42.3 sec
*1
, 6 ms to 46.0 sec
*2
, 8 ms to 63.4 sec
*3
(160 points)
*1. These values are obtained when the sampling frequency is 48kHz.
*2. These values are obtained when the sampling frequency is 44.1 kHz.
*3. These values are obtained when the sampling frequency is 32 kHz
-70
-60
-50
-40
-30
-20
-10
0
+10
+20
-70
-60
-50
-40
-30
-20
-10
0
+10
+20
Input Level
Output Level
dB
dB
Threshold
Width
