Tuesday, January 30, 2018

Audio Compression For Noobs

Of all the questions I get about plugins and how to use them, the elusive compressor takes the cake, hands down, no contest. So why is it that most people don't get it when it comes to compression? To contemplate that question, I looked back at myself when I first started mixing live in clubs when I was 19 (21 if the clubs ask). I didn't know what a compressor did either. Sooo, didn't use it. But as I got better over the years and watched others, I learned what it was supposed to do and how to get it to happen. I think one of the main reasons people don't understand compression is because it's mostly a transparent effect. I remember a guy back in the analog days who told me "If you can hear them working, it's too much". I don't completely agree with that now but it's pointing a noob in the right direction to say that, I suppose.

Now with digital everything these days, it's actually even easier. Some of these compression plugins have so many meters and controls that were missing in the old hardware days, that you kind of can't screw it up. Not to mention the ever popular failsafe called "presets".

The first thing I want to get to is explaining what some of the common functions are in compression tools.

Threshold: The threshold is your desired audio level. The more you turn it down, the more the plugin will compress in an effort to reduce the level of the audio to your chosen level/Threshold

FabFilter Pro-C2
Ratio: The ration is sort of how aggressive the compression will be. If you set the ratio to say 1:1, then the little compressor gnomes will sort of suggest nicely to the audio that it go back to the threshold line if it goes over. But if you set the ratio to 50:1 then the little gnome guys bring their swords and absolutely force the audio back to the threshold line.

Knee: This is how abrupt the transition will be between no compression and when it kicks in. A "hard knee" will be abrupt while a "soft knee" will be more subtle.

Attack: This will define how quickly the plugin reacts when the incoming audio raises above the chosen threshold level.

Release: Release sets how quickly the compression will fade off after it is triggered.

Makeup: Not the kind you wear on your face if you are in an 80's metal tribute, but the kind that brings the output level back up after the compression has brought it down.

Using compression on different types of instruments.

In the video below I show my personal technique for compression on a snare drum, a vocal, a bass guitar and a piano track. Just watching this video should give you a much better idea on how to use compression if you currently have no idea what you are doing.

Using compression on Sub-mixes and Mastering

An awesome multi-band mastering compressor is a must when mastering audio. In fact, it's the only thing I put on a master track other than a frequency analyzer to visualize where my levels are. Using a good compressor on a drum sub or vocal sub is also a must in my book.

The purpose of using a compressor on these types of tracks is slightly different from what we've learned above for individual instruments in that you are now using it to raise the levels and intensity while forcing the audio not to exceed the threshold. Aka "Punch".

Pentode Audio VTC-1
I use a compressor such as the Solid Bus Compressor or the VTC Vacuum Tube Compressor that ships with Mixcraft, for drum subs. Basically just gluing all the drum tracks together, leveling them and adding punch.

For mastering I use either the FabFilter Pro-MB or Yamaha's Final Master. Both are multiband compressors and both do an equally great job. The FabFilter is a bit more comprehensive though. You would use the multiband functionality to compress or intensify at different levels, each band. 

Here's a video showing my technique for submix and mastering with Multiband compressors.

I hope I've helped you to understand compression a little better than you did when you started reading this. Load a small project and mess with compression plugins until you get a feel for what controls do what. Happy squashing!

2 comments:

  1. Awesome! it will really help a lot of musicians to understand how this crucial effect works.

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  2. This is the most simple to understand yet thorough explanation of compression I have ever read. And I have been recording since the Tascam 4 track days! Thanks for a great tutorial!

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