FluidMoShun wrote:Everyone shut down my idea of using a compressor without really explaining what its for... So I just assumed it was just a lazy way to mix or something haha.
What a compressor does is tame transients of sound by a particular amount (ratio) over a specific amount of time (attack and release).
The probably most-used use of a compressor is to bring down peak transients to better match the rest of the overall volume of a particular sound. For instance you may have a snare sound, if you imagine how this waveform would look you'd have a massive spike transient at the start and then the decay of the sound after that. The loudest part of the spike will be where your peak volume hits (or where the channel fader shows -3dB or whatever it's coming in as). Along with peak volume, you also have RMS volume. This is the average volume of the sound, as in the volume that the sound is for the majority of time it's playing.
So, in a nutshell, you'll often be using a compressor to bring down your peaks to closer match your RMS volumes.
Ratio
So when you're compressing a sound the first thing you'll want to decipher is how much you want to bring down the sound to meet something else. In a drum loop for example, you might have a kick that's peaking at -3dB and a snare that's peaking at -5dB and you want the overall level of the drum loop to peak at around -5 but maintain a consistent level (as in - if you just turned down the drop loop so the kick peaked at -5, the snare would then peak at -7, but you want both the kick and snare to peak at -5). This is done using the ratio. If you want to tame your -3dB kick down to -5dB you'll probably want a ratio of between 2:1 and 4:1 depending on how 'effective' the compressor is.
2:1 would basically mean that a sound is turned down by 2dB for every 1dB that's over the
threshold. But generally all compressors are different and I usually find that 2:1 is only really effective enough for 'soft' compression uses. 3:1 is usually a good starting point for most sounds, then decide whether you need more or less compression later on.
Threshold
Next you need to bring your threshold down so that when your kick is hitting, the gain reduction is between 2-3dB so that your kick is bought down to the snares level.
Attack/Release
Is your kick starting to sound a bit flat and boring? Your attack is probably too low. Bring it up until the sound has its life back! The attack determines how quickly the compressor starts smashing that sound down. For transient sounds you'll want fairly high attack settings so that they're not pulling the 'snap', 'pluck' or 'hit' out of your sounds.
So imagine your waveform, the attack determines where through that peak the sound begins being cut, imagine that turning your attack up is slowly moving to the right across a waveform (very, very subtly).
The release determines how long the compression lasts for before dropping off and becoming an uncompressed bit of sound basically, with drum sounds you generally want this quite low that so the sounds remain vibrant and uncompressed because they're much quieter than the peaks anyway, but on other sounds such as string passages you might want your release a bit higher so that sustained sounds which have similar decay volumes to their peaks continue to be compressed.
Gain
Finally, bypass your compressor and see where the sound peaks on your channel strip turn your sound down so that the peak is at the level in the mix you want it to be. Now un-bypass your compressor and look at your channel strip level meter again, if your peak level is lower (which is should be, slightly) then bring your gain up a little to meet what the channel strip said previously.
What you've potentially done here is turn down the peak transient, then turned up the decay to meet that previous peak... Making the sound seem audibly louder in full (because it's the whole sound, not just the peak that's louder in the mix - without wasting too much headroom).
Now think of this in the instance of say a guitar passage where you have some bits that are slightly louder than others, if you want to level them out a bit... Use the above advice and play around with the parameters a bit until you get a desired result. The art of shaping sounds with compression is really in the attack and release settings, but I suppose a good ear for how much a sound needs to be compressed (ratio and threshold settings) is also just as important.