What is Compression?
May 29th 2012
Compression put simply reduces the dynamic range of a sound. This
‘squashing’ effect can be a valuable tool to tighten up mixes and
creative use of compression techniques can help you shape the overall
sound of your mix.
Let’s take a look at the controls you’ll find on most compressor plugins.
Threshold – this determines the volume level (in dB) that a sound must
attain before the compressor takes effect. When this level is exceeded
the signal is reduced (gain reduction).
Ratio – this control determines the amount of gain reduction applied to
the signal once the compressor has kicked in. A Ratio setting of 1:1
would mean that no gain reduction would be applied, where as a setting
of infinity:1 would mean that the signal would never rise about the
Threshold level (this is known as Limiting).
Attack – this control dictates the time that the compressor takes to
reduce the gain. Fast attack times will reduce the gain immediately
where as slow attack times will leave the first portion of the sound
untouched fading the gain reduction in. This is a classic technique
used to enhance the qualities of percussive sounds.
Release – this setting will determine the length of time that it takes
the compressor‘s gain to return to normal once the signal has fallen
below the Threshold setting.
Some compressors have an Auto attack/release button that selects suitable settings for the incoming sound.
Hard Knee/ Soft Knee – this control dictates the character of the
compression used, a Hard Knee setting will instantly apply the full
amount of gain reduction to the signal once it has exceeded the
Threshold. Soft Knee will allow the effect of the compressor to be more
gradual.
Side Chain – this function allows you to use an external signal to
control the compressor. This effect is frequently used in dance music.
For example producers will often feed the bass part from a song into a
compressor whilst routing the kick drum sound through the compressors
side chain input. This will have the effect of "ducking" the bass sound
when the kick drum plays, producing a rhythmic pumping effect.
Many plugin compressors lack character and sometimes it’s hard to hear
the effect they’re having. For instant gratification download Camel
Audio’s excellent free
plugin “Camel Crusher”. Disable the filter and distortion buttons and
route a sound through the plugin. Now turn the Amount control up and
notice the effect! We love using this plugin on bass lines and in tune
with other Camel products it has an randomize buttom!
See our glossary section for explanations of many music technology terms.
DMS
