Two compression attack and release myths to avoid

You might be surprised to know that two of the most common things that we’re taught about compression, regarding the attack and release settings, are incorrect. In this lesson, we’ll shed some light on two of the most common attack and release myths.

The compressor attack myth

If you search online to find out what the attack setting on a compressor does, you’ll likely read something like this:

“It controls how long it takes for the compressor to kick in”, or “it’s how long it takes for the compressor to start applying compression”.

Sadly, despite being one of the most commonly used ways of explaining the compressor attack time, this is actually incorrect.

The attack time will not introduce a delay or pause before the compressor starts applying compression. When a signal overshoots the compressor’s threshold, the compressor actually starts applying compression instantly. The attack time then controls the rate at which the gain reduction is applied. In most compressor designs, the attack time actually represents the time it takes for the compressor to apply roughly two-thirds of the gain reduction. So if the compressor was applying 6dB of gain reduction, the attack time represents how long it would take to apply 4dB of gain reduction.

So, rather than thinking of the attack time as introducing a delay before the compressor applies gain reduction, instead, think of the compressor attack time as controlling the rate at which the gain reduction is applied.

Despite often being taught incorrectly, the good news is that this change in definition probably won’t change the way that you use compression too much. You should still use a fast attack to apply the gain reduction quickly if you want to attenuate a signal’s transients. Or set a slower attack time so that the gain reduction is applied more gradually when you want to have a signal’s transients undergo little gain reduction. But the more you understand exactly how a compressor is applying gain reduction to your signal, the more control you have over the compression you apply in your mixes.

The compressor release myth

Another really common compression myth is one concerning your compressor’s release setting.

If you look into the compressor release setting, you’ll probably find it described as something like:

“How long it takes for the compressor to stop compressing once the signal drops below the threshold”.

This is, in fact, not the case.

Whilst the release setting does control the rate at which gain reduction ceases, the compressor doesn’t need to wait for the signal to fall back below the threshold to enter the release phase. The release parameter on a compressor is actually unaware of the threshold setting.

Instead, the compressor will release as soon as the provisional amount of gain reduction (determined by the ratio) drops below the applied amount of gain reduction. So, as long as the provisional amount of gain reduction is higher than the applied amount, the gain reduction increases at a rate which is determined by the attack setting. As soon as the provisional amount of gain reduction drops below the applied amount, then the compressor releases at a rate determined by the release setting.

If that sounds like a bit of a complicated explanation, then don’t worry! Just think of it like this… whenever you see gain reduction subsiding on your gain reduction meter, then the compressor is releasing, and the release setting is controlling how quickly that’s happening.

You can also think about the attack setting in the same way. Because the attack setting isn’t just relevant when the signal overshoots the threshold. The compressor responds to level changes above the threshold, too. So whenever you see the gain reduction increasing on your gain reduction meter, then the compressor is in its attack phase and the attack setting is controlling how quickly that is happening. Whenever you see gain reduction subsiding, the compressor is in its release phase, and the release setting is controlling how quickly that’s happening. So don’t be fooled into thinking that attack and release are only relevant as the signal crosses or falls back below the threshold.

Hopefully, this will go some way to furthering your understanding of the way that compressors apply gain reduction to the signals in your mix!

What’s your approach to setting the attack and release settings on your compressors when you’re mixing? Leave a comment below.