While EQ is used to equal out your vocals in all the frequencies, the compressor is usually used to boost the best parts of your voice using volume. It should bring forward the warmth and power of your voice, make the words you sing more clearer for people to understand, but most importantly should make the volume of your voice sound more consistent throughout the song.
Compression doesn’t work on the whole recording. Your settings will determine when it will work and when the original recording is good enough. You can find the window for the compressor clicking on the FX plugins of a track and then going to Dynamics > Compressor > Mono. A window looking something like this will show up:
When you go to the drop down menu above this screen, you can already access some preset compression settings for vocals. It’s great to play around with those or use them as a starting point to build your own.
Now, just like with EQ, there’s no one way to set the settings for compression. In fact the genre of music you make strongly influences this. The best thing to get familiar with is, what the settings stand for and to develop your ear for spotting when the vocals get to sound too compressed (which means all dynamics are just shot completely and the singer is sounding like a bit of robot or like they are talking on an old telephone).
Regardless on which software or which additional plugin you use for compression, the window usually will show two knobs: Release and Attack. I know, this sounds like sports terms, but what it means is the following. With attack you can set when your compressor should start a full compression and with release – probably no surprise here – you set when your compression should stop compressing.
The Attack and Release on vocals is usually set pretty low, so that compression will detect and work along with the dynamics of the vocals. You’ll also set the ratio low. You all have to find out what works for you best yourself, so don’t feel restricted by what you see in the sample screen above. That’s just what worked ok on my vocals on one of my tracks.
Now just like with EQ your looking for a balance. So with compression you will be taking away some volumes here and there and then giving it back elsewhere. The most important part is to set the Compressor Threshold so you create a certain gain (volume) reduction.
The Gain Reduction bar at the top will not only show you when the compressor is working or not, it’s showing you the output of your settings. As much as you get tempted to be led by what you see, you are working on sound, so feel free to look away or close your eyes when you are compressing and just go on what you hear.
Whatever volume you’ve reduced with your threshold setting, you will give back in the Gain. You are free to set your own values here based on your personal taste and music genre. If you have a very dynamic song or dynamic vocals (like rap vocals) you can turn the gain reduction up. Most of the information I’ve found about the gain reduction on vocals is that everything is fine within -5 and -12 db. I tend to try to not go beyond -8, because I’ve heard that number pop up the most.
Basically you work on the settings until you think it sounds good, check what the -db is in Gain Reduction bar and check what it sounds like when you set the Gain to the same. This means you’ve taken some volume from one end and added it back at the other. So what you let the compressor do, is push down anything that peaks. Whatever volume you have pushed down, you push back up in your gain.
Personally I’ve left the Circuit type to the default setting, but obviously you can play around with that too.
You also see a Limiter Threshold. A limiter is also a compressor, but it works the other way around. With a limited you set a maximum threshold for the full vocal track and then push the volume up of everything while the threshold is 0. I’ve not yet really been focusing on this yet, but it is intended for vocals, so worth Googling and researching.