Second only to the equalizer the compressor is the most used effect in audio. In most cases it is the very first effect that most producers and engineers learn about. In almost all cases we all started off learning about compression with a drum sound. This is because compression is easier to hear in a drum sound until you can train your ears to hear it within other instruments. We may be talking about some advance techniques so if you are new to compression or you just want a refresher then you might want to go back and read our Understanding Audio Compression article before continuing.
So the question of how much compression should you use could mean how much compression on any given signal or it could mean how many compressors should you use on a signal? Since we are not really sure which of the two the question was meant to address, we will attempt to answer them both.
First let's have a quick refresher on compression. Let's take a look at the five basic areas of a compressor.
THRESHOLD – Sets the level where the compression will take place.
RATIO – Sets the degree of compression that will take place.
ATTACK – Once the signal is above the threshold this determines when the compression will start.
RELEASE – Once the signal is below the threshold this determines when the compression stops working.
GAIN – Mostly known as make up gain this is used to make up the peak level that was lowered by the compression.
If you want more info on compression take a look at Understanding Audio Compression.
HOW MUCH COMPRESSION ON A SIGNAL?
The question of how much compression should be on any given signal is almost impossible to answer as it really depends on so many factors. It depends on the signal itself, what you are wanting to accomplish and why you are compressing in the first place.
WHY AND WHEN TO USE COMPRESSION?
Compression is used for lots of different reasons, so first you need to decide WHY you are using it and WHEN is the best time to use it.
Here are the three most common reasons;
One reason is to limit
the dynamic range of a track or instrument. The dynamic range is the
range between the loud and quite parts of your song. So if part of
your song has a really loud guitar let's say and a quite piano, then
the difference between to two is the dynamic range for that
Another reason to use a compressor might be to avoid distortion or clipping. This is when the signal is too hot and is peaking above the zero threshold. As we have already learned by setting the ratio, attack and release we can control the signal going above a threshold and stop it from clipping the signal.
You could also use compression on an instrument that has very little or no substain. In this case it is possible to use a compressor on a note from that instrument making the note last longer giving it more substain.
WHEN – You use
compression when you are trying to avoid clipping or you are trying
to change your dynamic range or you want to substain a note or sound
in a instrument.
HOW MANY COMPRESSORS SHOULD YOU USE?
Think of a compressor like layers of clothing that you could wear outside. If it were cold you could put on several light jackets or you could put on one heavy coat right? It would not really matter if you wore one or three jackets because the issue is the cold weather and not the number of jackets that you are wearing. You want to use the same approach when it comes to your audio signal. This real issue is to know what is the issue with your signal and why are you using a compressor to address it? If you figure out the what and why it always makes the how easier. So if you are not sure then refer back to the what and why. The one thing you do not want to do is to compress because you always do or because some one told you to do it that way. Compress because you need to not because you have to.
USING TWO COMPRESSORS
One of the easiest tricks, but also one of the most difficult to do correctly is using two different compressors on your vocal signal. Why would anyone want to do this you may be asking? Well there are lots of reason why you would want to use multiple compression as we already discussed but on a vocal signal you may want to tame a vocal.
TAMING VOCALS – Sometimes you have a vocal that you need to tame but if you use a compressor on it you can hear the compression happening and you may not want that. Using two compressors maybe to tackle the top with some fast compression and then using another compressor to shape the vocal signal just may be the answer for a stubborn vox.
The key; is to know your compressors and marry up two that work well together. For example you may not want to use an 1176 compressor long with the Antress Modern Seventh Sign because they are both fast compressors. As a matter of fact the Seventh Sign is meant to be a 1176 clone so these may not work well on slower songs like ballads or r&b stuff, but would work on dance vocals or rap.
Compression gets easier the more you work with it and the more you learn about it. Compression is not the easiest thing to grasp, but if you keep at it and practice with the same set of compressors until you know them very well, you will have a moment where it just seems to all make since and you will be asking yourself what was all the fuss about.
Stay tuned for more weekly tips and tutorials every Wednesday.
Article written by Alex Butler
Alex is an audio engineer, studio producer and freelance writer based out of Seattle, WA.