Understanding Your VS: Compressors/Limiters

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The device most commonly used for controlling dynamics is a compressor/limiter. A compressor/limiter reduces the difference between the loudest part of a performance and the softest. There are basically two reasons you want to do this:
- First, if the loudest parts are too much louder than the soft parts, you’d have to record them at an unacceptably low level so that distortion doesn’t occur at the loudest parts; if you’re mixing, the quiet parts may disappear in the overall mix.
- The second reason you might want to use a compressor is to make a performance sound tighter and somewhat more “record-like” by making its dynamics more constant.
Here is a brief description of some of the parameters common to most compressors:

Threshold- sets the amplitude level at which the compressor begins to function. When the input level is above the threshold value, the compressor begins to work.

Ratio- The ratio control determines the amount of input level to output level. For example, 4:1 ratio means that for every 4 dB coming into the compressor above the threshold setting, 1 dB will be output.

Attack Time- the attack time setting controls how fast the compressor begins to attenuate the signal after the input signal has gone above the threshold level.

Release Time- The release time controls how long the compressor stays on after the signal drops below the threshold level.

Output Gain- The output gain is used to adjust the output level of the compressed signal.

A compressor and a limiter are basically the same thing, except that a compressor uses a ratio of less than 10:1 and a limiter uses 10:1 or higher. With its higher ratio, a limiter’s threshold is like a brick wall that the signal will not be able to exceed.