Compression

COMPRESSION

Compression at first too me a while to get your head around but the more I dove into it and the more I understood what the controls did/do and how it is shaped my music I understood how important compressors are. Originally Compressors/ Limiters was used to protect over modulation, this could occur when a signal that was being encoded onto the radio signal, A compressor automatically reduced the volume level when the signal went over a threshold, you can still hear this today on the radio when a presenter shouts or there is a loud noise, the compressor catches the volume over the threshold and reduces it regarding to what setting its has been set too, and then gradually or sharply comes back up to normal levels.
​Below shows the main controls for Compression/ Limiters and a brief explanation on what they do.

CONTROL'S OF A COMPRESSOR/ LIMITER
​

• ​​Threshold - Is the level set at which the compressor starts to work, sounds below the threshold will not trigger the compressor to become active but sounds above the threshold will activate the compressor.

 

• ​Ratio - This is the difference between the input and the output levels, e.g a 4:1 ratio is input 4dB to the output 1dB, The higher the ratio 10:1 + the more the compressor is becoming a limiter.

 

• Attack - This is how quickly the compressor reacts to the signal that is above the threshold, it is usually in milliseconds (ms), high values will allow peaks through as short fast values will attain the peaks. Some compressors allow a look ahead of a set ms (1.5ms, 10ms etc) this will allow the compressor to catch the peaks and also allow some compressor attack values to be set at 0.00ms. 

 

• Release - This is the length of time that the compressor take in order to return to its 0dB, in ms values can be long short or in some cases automatic allowing the compressor ride the signal back up to 0dB

 

• Knee - This is only found in a few compressors, the choice is usually between soft and hard. In Ableton Lives 10 compressor you can set the value between 0db and 18db with 0dB being hard and 18dB being soft.

 

• ​Make-up gain - As compression is lowering the signal level the make up gain is use to compensate for any loss in volume, when doing this make sure to bypass and reactivate it to compare and to see if it is actually making your sound any better. 

 

• ​Sidechain Input - Again not on all compressors but this allows for side chaining input, a video example can be found HERE.

​Ultimately it's personal to how you use compressors, giving a overall reducing by 2-4 dB with a 2:1 ratio gives a gentle glue to a overall mix whilst a 15dB reduction and 10:1 ratio will give a slammed feel and bring out the tails in your mix, Its a personal thing.

​DL