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Compressors are a type of signal processor and can be thought of as a kind of “automatic fader”. They are used either to fix problems, for example, too great a dynamic range in the recording; or to enable creative mixing for example, by adding presence to the sound track.

So how does this work?

When an audio signal passes through a [tag]compressor[/tag], it can:

• lower the volume of the loudest parts of an instrument or mix
• raises the volume of the quietest parts
• reduce the dynamic range of the signal overall

This means you can increase the signal’s overall level, without clipping.

In simpler terms, the loud parts of an instrument or mix are quieter and the quieter parts are louder, giving a better balance, and suiting the recording for a wider range of listening environments. You can enjoy the string quartet in your car, amongst noisy city rush hour traffic, instead of having to wait until you’re in your home theater.

Consider Compression to be an art.
Do you feel the track would benefit from compression? Are the quiet sections too quiet or the loudest sections too loud? Then introduce it – a little at a time.
But take note – compression is not always necessary. If applied incorrectly it can result in your track or mix sounding awful instead of awesome!

So, compressors are used to enhance your sound tracks.

There are two main types:

• Upward – raises the volume of the quieter sound sections
• Downward – reduces the louder sections

The term “compressor” arose because they originally only reduced the level of the louder sounds.

Compression settings are typically characterized by these parameters:

Output Gain – When you compress an audio signal by a certain amount (measured in dB (Decibels)), the louder parts become quieter. The output gain allows you to compensate for the reduction in levels in the loudest section of the signal that has been compressed.

Threshold – The volume level at which compression starts to take effect. You set the threshold to where you need it, depending on the mix.

Compression Ratio – A measure of how much compression is applied to the sound signal.

Attack time – This refers to how tolerant the device is when a signal exceeds the set threshold. The attack determines how rapidly the compressor reacts to the signal. Depending on this setting, shorter sections exceeding the threshold will be ignored, but longer sections will be compressed.

Release time – This controls how long the compressor will stay in effect once the signal falls below the set threshold value.

Knee – This parameter determines how quickly an audio signal reaches full compression once over the set threshold.

When a compressor is fed an audio signal, it measures the signal level to determine whether to apply processing, or not. If the signal remains below the threshold, compression remains off, and the signal is not affected. When the signal level does exceed the threshold, then compressors react using the attack speed parameter and reduce the signal level according to the settings of the ratio and knee parameters.

In the next part, we’ll introduce how to use compressors in your music production process.

Looking for Compressor Products? Just see the “Related Posts” list below for access to product descriptions and reviews.

[tags]threshold,compression ratio,attack time,release time,knee[/tags]