(cont)
If a very high compression ratio is used (some compressors have
an infinity setting on the ratio control) then the compressor
acts as a limiter. This means that however much the input
signal increases, the output signal stays fixed. Limiters are
used to protect speakers from potentially damaging 'spikes' of
power which could damage them.
The controls you see on a compressor are:- |
|
Threshold |
Sets the level above which compression takes
place |
|
Ratio |
Sets the amount of compression |
|
Attack |
Sets the amount of time the compressor waits
after the signal rises above the threshold level before applying
compression. This can be used to let the initial sound through,
a technique that preserves the power of some sounds, particularly
drums. |
|
Release |
Sets the amount of time the compressor keeps
applying the compression after the input level has fallen below
the threshold. Too fast a release time gives audible 'pumping'
as the level fluctuates rapidly, too slow, and soft passages
may be lost. |
|
Output Gain |
Compression will tend to make the output signal
sound quieter. This control increases the overall output level
to compensate for this. |
|
Click here
to see a picture of a compressor front panel
If you are using a compressor for musical dynamic control, I
would start with soft-knee settings at ratios of 2 or 4:1 and
the threshold at 0dB and then adjust the attack and release settings
by ear. If the unit has meters showing the amount of gain reduction
and output level, these can be a useful guide to further ratio
and threshold adjustments. previous page |
|
|
