What is a Compressor?

What is a Compressor?

Author: AVG Admin
February 11, 2021

What is a compressor? Well it used to be a thing in the rack over there that everybody thought they needed, but no one is really sure how to work!

Like Rey in The Force Awakens, I often “Bypass the Compressor” at churches I visit to teach mixing concepts, and it usually improves the sound because the compressor is set so poorly.

On a digital mixer, it’s a mysterious button called “Dynamics”, or the even more mysterious “Dyn”. It comes up as the most popular thing I teach about, second only to EQ.

In the simplest terms, a compressor is an automatic volume control, designed to quickly lower the peaks of a sound.

I know – you can configure some compressors to expand peaks up, too!”
But if you already know that – you know enough about what a compressor
is already. This article covers the basics of what a compressor is and why you use them.

Anyway, a compressor has controls for changing the peaks of the sound, and to do it so quickly, you can’t hear it. Supposedly. This has the effect of limiting the dynamic range of the sound you’re compressing. I’ve noticed in a lot of churches I go to, what the sound techs think the compressor is for, is to control the volume of the entire Sermon, so they don’t have to touch the faders for an hour, while they drink their coffee. That’s not what they’re for.

They’re really used to help voices and instruments sound more even, which helps them to be heard better in a mix. And since you’re normally just lowering the volume of the peaks, you can raise the overall, or average volume of the voice or instrument, using Gain, to make it louder. This will make compressed sounds easier to hear in a mix. Also, If you remember your Fletcher Munson curve, as things get louder, the frequency response of your ear flattens out; So you hear the bass and treble more evenly, and the harsh frequencies are damped more.

The net effect is, compressed sounds, sound “warmer” and less harsh, and since you can hear low frequency sounds much better when they’re loud, sounds that are primarily low frequencies, like Bass, Kick Drum, and Toms, are much easier to hear when they’re made louder using a compressor.

For singers, it also makes them sound, well, better. I’ve noticed that really great singers have incredible breath control. They’re able to control the volume of each note very precisely, for the entire length of the note. Average singers, can’t do this.
They tend to surge in volume at the beginning of notes, waver in the middle, and run out of air, before the end.

It’s almost sub-conscious, but you perceive that kind of singing to be uncontrolled, weak, and not as good. But compression, can correct this. - well at least some… and make an average singer, sound much better. Used in a subtle and gentle way, it can make a great voice, sound spectacular. It has the same effect on a speaking voice, as well. Compression will make the voice warmer, more present, and more controlled. And, Pastors, easier to hear.

So think of compression as the spice that makes things tasty, you don’t need it on everything, but if you don’t go overboard, it can really make some things, great. This blog will give you the background to go on to the “Controls on a Compressor”, and “Compression Tips and Techniques” .