Compression for Dummies

A compressor is a signal processor that alters the loudness of a signal; as the name implies, it compresses the dynamic range of an audio signal. This indicates that it softens the loud signal and makes the soft signal a little louder, reducing the disparity between the loudest and softest portions of an audio stream.

Compression is unavoidable in a decent mix; not understanding how to utilize the compressor correctly might ruin your mix.

One of the most crucial mixing techniques you can learn is how to operate a compressor.

Parameters of a compressor.

The majority of compressors have five parameters in common: ratio, threshold, attack, release, and makeup gain. And this is extremely important that you know your way around a compressor very well.

1. Threshold

2. Ratio

3. Attack

4. Release

5. Make-up Gain

Threshold. The threshold is the minimum limit that when crossed by an audio signal compresses the audio. For example, if the threshold is set to -10dB and the input sound peaks at -12dB, the compressor will not be activated and hence will not compress. But on the other hand, if the set threshold is -10dB, and the input loudness peaks at -8dB, the compressor will be activated and it will start compressing.

Ratio. The ratio defines the degree or amount of compression. In simpler words, it means that the ratio defines how much compression takes place. For instance, a ratio of 4:1 (Four is to One) means, for every 4dB increase in input at the input of a compressor, there will only be an increase of 1dB at the output.

For example, when the signal crosses the threshold (set at -10dB) and reaches -6dB, which is 4dB more than the threshold. the output of the compressor should reach -9dB (which is 1dB over the threshold).

Attack. How fast a compressor turns ON after the signal crosses the set threshold is called an Attack. Usually set in milliseconds (ms) , the attack value that is safe is around 20ms to 30ms. An attack too fast can alter the low ends of a signal and compression too slow wouldn't even compress the signal.

Release. How fast a compressor turns OFF after the signal drops below the set threshold is called release. A release too fast can alter the frequency content of an audio signal in undesired ways and a release too slow wouldn't even turn OFF the compressor.

Make-Up Gain. Once the compression is done, we lose a significant amount of loudness which is then recovered by Boosting the Make-Up gain. For example, if the compression or Gain Reduction of an audio signal is 6dB, then the safe way to recover the loudness is to give a Make-Up gain of 6dB.