Recording with Compressors

For most instruments and all vocals it is good to put compressors in the signal path, they can simply be added via the insert (if you have them) or put inline, in between the desk and the capture device. Only use a very small amount of compression, as you don’t want to limit your mix before you’ve even started.

Let’s start by explaining all the different features of a standard audio compressor.

Threshold

The threshold is the level at which you want the compression to start to affect your audio signal.

Say you set your threshold at -20db, but your audio signal never gets close to -20db, then the compression will never kick in.

On the other hand, if you set your threshold to -80db, pretty much every audio signal will be compressed by the compressor.

Ratio

The ratio is the amount of compression you want to apply to an audio signal. Or you could say the ratio is the amount of audio reduction.

When an audio signal reaches the compressor threshold, the compressor reduces the sound by the amount set by the ratio.

It is common to have a ratio of between 3.5:1 and 4:1 for vocals. It all depends on how dynamic the vocalist tends to be. If the singer is very timid then 3:1 would be more than adequate, however, if a singer loves to shoot then a ratio 4:1 or even 5:1 would be required.

Attack

Attack is simply the amount of time it takes for the compression to kick in.

If you wanted to compress a trumpet, you would normally want to use a fast attack, (although trumpets can play softly) because you will want the very start of the first note to be controlled by the compressor.

Also, you might want to compress an audio signal, but you don’t want the clarity to be removed when you compress the signal, so setting a slower attack allows more clarity to be heard.

Hold

Once the threshold has been reached, the hold determines how long the compression will stay active until releasing the compression.

If you are compressing a drum kit you don’t want the compression going on and off, you want the sound to remain constant, so by using the hold dial, you can bridge any small gaps that go below your threshold using the hold dial.

Release

Attach controls how quickly the compression is removed once the threshold is no longer reached.

If you have a peace of music that you are compressing, you don’t want the audio signal fluctuating or pumping when you are compressing it. You need to increase the release so that the compressor doesn’t come off so soon.

The last thing you want to hear is your audio signal getting louder when your audio signal should be getting quieter.

Range

Kind of like a mix dial, it allows you to mix the about of signal that has compression with the original signal that has no compression. This dial is useful when on a mixing desk channel insert where you might not want all the sound sources compressing.