If there is one thing I get asked about more than anything else when it comes to audio, I would have to say it’s compression. Yes, compression. It’s elusive, hard for even a trained engineer to use, and yet so vital to a good mix it must be given the proper amount of attention and practice. Modern studio and live engineers use more compression then they would care to admit to, but the key is learning when too much is actually too much and damaging to the source material. In this first part we’ll look into what compression is and how it functions. Then we’ll explore settings in part 2.
Compression is actually distortion. Yes, distortion like your electric guitar distortion but nowhere near as obvious unless you want it to be. Therein lies the challenge. How much do you use? And for that question I have developed a “magic number” if you will, much like a guitar shape you can use across a fret board. Before I get to that though let me preface.
There is no substitute for learning how to truly listen. Can you tell the difference between the timbre of a Fender Stratocaster and a Telecaster in a recording? Or between a 6.5 X 14 maple snare and the same size in brass or aluminum? If not, then you still have some work to do. Learning to tell the difference between instruments in the same family is a trait associated with good engineers. The reason is because they’ve learned how to identify problems in their mixes sonically and are now to the point of recognizing the tonal differences between like instruments. I say all that because better listening enables you to dial up better settings on your compression, not to mention everything else too. It all takes practice. You’ve heard it a million times and it really is the truth. Practice makes perfect(or better anyways).
That being said, I want to delve into this issue of compression. When I was learning how to use a console and outboard NO ONE told me where to start with a compressor. Everyone I talked to had an idea of what they did but no one used them the way modern studio mixers use them. No one I knew used them to get that “in your face” “punchy” “engaging” sound we hear all the time and love in modern recordings. The settings I’m going to list are as a result of years of fine tuning, recording, live mixing, and gathering of valued opinions. The funny thing is I haven’t got it all right and still want to make things “better.” Thats where the creative part of the whole process can become very subjective. But I digress.
So primarily we’ll be dealing with a pop/rock setup as most modern churches have gone in that direction with the worship style. Pop/rock meaning we have drums, bass, electric guitars,acoustic guitars, piano, keyboards/synth, vocals, the occasional stringed instrument and a steryeryo bus or “master output.” Now before I delve into the settings let me explain what the nobs on a compressor do.
On your typical compressor you have a couple of nobs usually in this order: threshold, ratio, attack, release, knee(sometimes), and gain. Your compressor might also have something that says “gate” or “expander” which are two different names for essentially the same thing. However, that topic will have to be dealt with in another blog. So back to compression. Below you’ll find the names of our compressor nobs and what they really mean to you.
- Threshold-like that of a door, is a line. This line can be adjusted up or down within the audio signal. The threshold does nothing more than tell the compressor where to start compressing your signal.
- Ratio– Yes, just like in math this is a real ratio. So you’ll probably see some settings here: 1:1, 2:1, 4:1, 6:1, 10:1 etc. This nob is basically where the sound or tonal quality of a compressor comes from. The numbers mean one thing and one thing only. Don’t let anyone tell you otherwise. 4 to 1 or 4:1 means that for every 4 four decibels that pass the threshold the compressor will let 1 out. Essentially you are controlling how hard you compress here.
- Attack– This is usually measured in milliseconds. The reason for that is because most of the transients or “initial impulses” you hear that need to be controlled don’t last more than 1 second which is………..all together now……….1000 milliseconds. For example a single snare drum hit usually isn’t longer than 30 to 50 milliseconds depending on how it’s tuned and how tight/lose the snares are. The attack adjusts when the compressor starts compressing after the signal crosses the threshold. You could basically view it like a second threshold.
- Release– Again this is usually measured in milliseconds. The release adjusts how long the compressor is going to clamp down on the signal. It is called release because essentially by telling the compressor how long to hold down you are also telling it when to let go or release the signal. The reason you have to be careful here is because if you set the release to long you will start to miss transients. For example if the release is set to long on a snare and say the drummer plays a 16th note snare drum fill(which is common to pop/rock) the first hit of the fill may come through fine but the remaining should become more quiet as the fill progresses in time. The right idea is that your release covers the transient you are trying to control and only that transient not the subsequent until the compressor has fully released.
- Knee-This setting basically adjusts how aggressive the audio will sound passing through the compressor by adjusting the attack and release curve. The options are from Hard to Soft. Hard being the most aggressive and Soft being the least.
- Gain Makeup– This is where we make it “in your face.” The gain or make up is just like turning the gain or trim nob up on your console. Except when it is done on the compressor the sound comes right up in your face. The reason for this is because you have controlled the peaks of your content by turning them down very fast with the compressor. Your peaks are closer to the valleys or quiet parts so now you can make up the difference that you’ve turned down them down with the gain nob. Which brings me to the last control which isn’t a nob at all
- Gain Reduction LED’s– This will look like a row of small lights somewhere on the face of your compressor. Typically these are green or yellow and red. This meter tells you how much you are compressing or reducing the gain. Every time that snare hits you should see the meter register gain reduction, usually signified by red lights with negative decibel readings under them. This is telling you how many decibels you are reducing the peaks by, and it is telling you how much gain you need to make up as a result of reduction.
Tweak 