Understanding & Using Compressor Limiters for Audio Compression

Compressor Limiter

The Understanding Compressors Tech Sheet from mixtheband.com show's how to use audio compressors

This great Tech Sheet explains how to
Set Up and Use Compressor Limiters

What is a Compressor Limiter?

A compressor simply reduces the difference between the loudest and quietest parts of a piece of music by automatically turning down the gain when the audio signal gets past a predetermined level. Compressors often have a limiter setting which rather than just reduce the volume the limiter stops the signal getting past the level altogether. Audio compressors are very popular with alot of live and studio engineers as they allow greater control of audio signal from both musicians and singers and can really help control the mix. The key when using compressor limiters is very often to even out the voice or instrument so that there are less peaks in volume and then the overall volume of the channel fader can be higher and overall the singer or instrument can be louder in the mix. Understanding how to use compressor limiters and incorporate audio compression into your mix will give you greater control when you mixing both live and in the studio. The above Understanding and Using Compressor Limiters tech sheet both explains and shows you how to hook up a compressor limiter and also shows what leads you need, how to patch them in and the best settings to go for when applying audio compression.

Typical Compressor/Limiter Applications
Audio Compressors are used on Vocals, Bass, Keyboards, Guitars both acoustic & electric, Kick & Snare drums etc.

Limiters are generally used in between the desk and the amplifier to prevent too much signal being sent to the amplifier causing it to overload then clip and distort.

Why Compress?
To control peaks in volume eg screaming vocal, slap bass guitar
To alter sound eg fatten kick drum or bass
To bring out certain tracks eg Vocal
To smooth out mix tighten it up eg on drums
To change the bass or high content in track or mix eg frequency conscious, de-essing
or compressing bass part of acoustic guitar
To get more volume out of sound system
To Duck sound (used by DJ’s)
To protect sound system (when used as limiter)

Some Typical Compressor Limiter Functions

Threshold - Sets the point at which the audio compression starts. If the sound is not loud enough to get above the threshold the compressor limiter does not react. Above the threshold the compressor reduces the volume automatically to keep the signal from getting too loud.

Ratio - Is based on dBs, so if a compression ratio of 3:1 is set, an input signal exceeding the Threshold by 3dB will be compressed so there is only a 1dB increase in level at the output.

Attack Time - The attack time is how long a compressor takes to pull the gain down, once the input signal has reached or exceeded the Threshold level. With a fast attack setting, the compressor works almost immediately, whereas a slower attack time will allow the start of a transient or percussive sound to pass through unchanged, before the compressor gets its act together and does something about it.

Release Time - The Release sets how long it takes for the compressor's gain to come back up to normal once the input signal has fallen back below the Threshold. If set too fast it can cause pumping of the sound and too slow can mean the sound takes too long to get back to normal volume.

Hard Knee - Starts compressing as soon as signal passes threshold.

Soft Knee - Starts to slightly compress say 10dB before threshold for more subtle compressing. As the input level increases, the compression Ratio is automatically increased until at the Threshold level, the Ratio has increased to the amount set by the user on the Ratio control.

These are just some of the audio compressor settings you are likely to use but to learn more on exactly how to set them up and use them click the following mixtheband.com compressor tech sheet;
Set Up and Use Compressor Limiters