To Compress or not to Compress?

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A basic look at pre-recording and post-recording compression and reasons to do them

This article was prompted by a thread in our forum, and after a lengthy thread on the subject one member suggested making it a recording tip, I agree, it is a worthy tid-bit of knowledge so here we go:

Many people are confused by compression (along with many dynamic effects) and don't understand why to use it, and more importantly when to use it. Compression is nothing short of a magical little effect that will raise the level of quiet signals and at the same time clamping down on the really hot signals, therefor "compressing" them into a more even signal. So, most people will first ask why do you want to do that? don't you want the rawest signal to get the most accurate sound to tape? Well, no, not always. As an example I will use a typical vocal track, as it is the most dramatic example.

When a vocalist is in the iso booth doing his or her thing it is human nature to let the music take control, therefore, the singer starts moving around, bobbing the head or whatever. In doing this the mouth moves closer to and farther from the microphone while recording, in addition, if a singer doesn't take a breath right on cue the first word or two of a phrase may come out quieter than the rest. This leads to an inconsistent and very raw, nasty sounding track as the engineer has to constantly be riding that fine line of not letting the track clip on the hot signals and not letting the weak signals drop off the recording.

Enter the compressor. With the proper settings (which we have discussed in a different article) you can give this nasty sounding track a consistent and yet still dynamic recording that is more pleasing to the ear and easier to work with in final mixdown.

The trick in doing this is to not compress to much, if you over-compress any signal you can suck the life right out of it, leaving a unemotional track, which, in some cases may be what you are going for, but generally not.

Another instrument that is commonly compressed pre-recording is drums, kick and snare is often compressed, as well as limited and gated. The limited and gate can in many cases by used with a compressor to further process a nice clean signal for the recording, these are discussed in the same article mentioned above.

Post-recording compression can be used on any track at any time the artist feels it is necessary, even adding yet more compression to tracks that already had some during the original recording. During premastering/mixdown the additional compression is used more to make each instrument fit in the mix together so no signal get totally out of control or takes over the sound stage. This being the case is yet another reason to make sure not to over compress on the original track, because more can always be added later.

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User-submitted comments

Mar 25, 2006 01:05 pm
prerecord compressing!
I fully agree with some very lite and easy compression on vocals, bass and kickdrum, but if you are new to dynamic prosessors you should be very careful with what you do.
You can totally mess up you recordings with wrong and to heavy compression and when you have that on tape or harddrive there's nothing you can do to repair it.
So my tip is lite and easy compression on bass, vocals and kickdrum.
Bass you can allow a little harder compression, maybe up to 8 to 1 in ratio and up to 4 dB compression.
On vocals no harder compression than 3 to 1 and somthing like 2-3 dB compression.
Kickdrum you can allow a ratio of around 4 to 1 and 2-3 dB compression.

Hope this helps

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