Compression can be a tricky one to get your head around, and even if you've got your head around the threshold and ratio settings without the attack and release times being set correctly it will always be difficult to get the desired effect. This quick tip will outline a really handy trick I learned from a friend a few years ago which allows you to get your attack and release times just right. It's primarily designed to work on drums but the same principles will apply to any percussive sound.
The Attack Setting
In this first example I will use the standard compressor that comes with Cubase to compress a kick drum. Drop a compressor into your kick drum channel, or group if you are using more than one kick sample to make your drum. Here is how the drum sounds without compression:
Lower the Threshold as far as it will go, and increase the ratio all the way. You should hear that the drum sample(s) are being horribly over compressed. Now lower the attack time to the shortest setting possible. Your compressor panel should now look like this:
If you slowly creep up the attack control you will hear the sound start to 'click' - when the click becomes fairly pronounced you know that the transient 'attack' on the drum is coming through, and that your attack setting is correct:
Now that the attack is set correctly we can return the threshold and ratio controls to something more reasonable - in this case I have set the ratio to 5:1. Now raise the threshold to a level where you feel the drum start to come back to life, and let it settle there. It's also a good idea to turn the makeup gain off auto and manually set it to a level so that the drum sounds the same volume when the compressor is bypassed as when it is left in. Here is a before and after of my kick drum:
The difference is subtle, but you should be able to hear that the second set of kicks sound more punchy and controlled, with less 'fluffyness' to them - this will really help them sit in your mix. Here is a shot of how my compressor is now set:
The Release Setting
Setting the release is also important, as if the compressor has not 'switched off' before the next drum hits you will have wasted your time setting the attack control! As a general rule you're going to want to have the release control nice and snappy, but you can get some strange effects if you lower it too far. A good guideline is around 200ms, but it's a good idea to check that your compressor's gain reduction meter has returned to zero (or thereabouts) before the next drum hit sounds - you may need to use a shorter release time but make sure you listen carefully for any unwanted effects.
Another Example - Snare Drum
Just to clarify things I'm going to go through the technique quickly once more, this time with a clap sound, and using the M-Class Compressor in Reason. As before simply load in your sound and run it through a compressor. Here's my clap sound with the compressor bypassed:
As before, we need to first apply some ridiculously heavy compression, so I've turned up the input gain and the ratio as high as they will go, and lowered the threshold right down. Reduce the attack time to the shortest possible, then creep it up so that 'pop' starts to come through like this:
You should be able to really hear that 'smack' coming out. Now return the ratio and threshold to more normal settings, I've used a ratio of 2.65:1 and a threshold of -28.6dB to result in about 4db of gain reduction, though how much you compress is up to you. With the release control, again you shouldn't have too much trouble, but about 200ms is a good guideline. Here's how my compressor looks:
A Few Final Tips
Remember that after compression you may well need to EQ a little bass back into your sounds, as compression often affects the energy heavy lower frequencies. Also, if your drums are going to be compressed again after this initial compression(ie more than one snare is going to a bus to be compressed all together) then you may need to be more gentle with your gain reduction to avoid over compression.