Compression question(s)...

[Crayon Boy]

I have recently been discovering the joys and tribulations of compression for the first time. I am to the point where I've got a good feel for compression... I understand how it works and how/when to squash a signal. My question is twofold... first off, I've noticed that a really low threshold really boosts the volume of the quiet parts of a dynamic track. Can someone explain why this happens?? Second question... what if I have a very dynamic track and I'm squashing the loud parts, but need to bring up the softer parts of a track. Lowering the threshold doesn't make sense because I want the compression to kick in at a certain point to squash the loud parts... will raising the ratio bring up quieter passages?? Any tips here would be much appreciated.

[tubedude]

Output gain, baby! Shave the peaks, turn up the lows...

[Crayon Boy]

OK... I'm a bit slow. Explain the output gain thing to me.

[Track Rat]

The threashold controls at what level the compressor starts compressing (if it's set to -10dB, everytime the level goes above -10, the compressor will "compress"). The ratio controls the amount of gain reduction that will take place (2:1 ratio means for every dB above the ratio, gain would be reduced 2dB, etc). Attack controls how fast the compressor reacts and release controls how long before the compressor "lets go" of the signal. The output gain control makes up for the gain you lost when the compressor "compressed".

[Crayon Boy]

I know what the treashold, ratio, attack, and release do... I wasn't sure what the output gain did, but I figured it raised the overall volume of the track being compressed. I still feel like my original question is not being answered. Now I am confused... so let me ask this... let's say I'm listening to a mix. The dynamics on the kick drum vary wildly... some parts are very loud, clear, and distinct... other times it can barely be heard because the drummer hits softer when doing the fast double bass parts. I watch the levels and hear that I like the levels when the kick is hitting around -4 db, but I don't like anything over that. So I set the compressors threashold to -4db... that takes care anything that goes over -4db, but what about when the kick gets quieter and needs to come up more?? Is there a way to compress to squash the loud and bring up the low parts?? Or would I have to ride the fader on the kick and bring it up at the quiet parts? Would raising the ratio bring up the quiet parts? Is Tubedude saying to raise the output gain and then squash the heck out of the signal so everything sounds loud??

[Blue Bear Sound]

Not really... you're thinking of the signal in terms of a peak only, and not thinking in terms of a dynamic range window (ie the difference between the softest kick and the loudest kick). It is this window that you want to narrow if you want the dynamic levels to be more similar (as if the drummer played at a more consistent level).

To do this, you set the threshold to a point (by ear - not dictated by a peak level you see on the meter) that brings the dynamic range into the "level window" you want to work in.

It ain't about the meter numbers, or even the numbers on the knobs, it's about what your ears are telling you!

[Crayon Boy]

Ok... I am getting the point... I have to think outside the box and trust my ears. One more question, though... if the threashold dictates the "level window" where does the ratio come in?? I understand that the ratio is how much the signal gets squashed, but how can I get a grasp on ratio when numbers don't mean anything? Just trying to get an idea of how to think about the ratio now. Sorry for all the questions... just really interested in this stuff and trying to get it to come together in my mind.

[dirtythermos]

Let's say you set the ratio to 10:1 or higher (which you would call limiting). Then anything above the threshold gets "squashed" right down to the threshold. From there, start backing off the ratio. The more you back it off, the more above the threshold the compressed stuff is going to be.

In other words, the ratio is how "severe" the compression will be.

[Crayon Boy]

OK... now I'm really starting to grasp all this. Now can someone give me a good example of what output gain does and an example of how it would be used?

[Big Kenny]

If you are not getting a "hot" enough signal to your recording device (because you compressed it) you would increase the output gain
Also, there are a lot of different finalizing tools that will "optimize" or "normalize" a track. Depending on what tool you use. it will bring quieter levels up to pre determined levels and/or limit peaks. I don't know what your set up is but look around
In His Name
Big Kenny

[Strange Leaf]

Originally posted by Crayon Boy
OK... now I'm really starting to grasp all this. Now can someone give me a good example of what output gain does and an example of how it would be used?

As a simple rule, even though there are no rules, turn the output gain up to boost as many dB as the compressor reduces on the materials peaks.

If you compress a bass for instance, and you set your compressor up to tame the peaks by, say 4dB. Turn the output gain knob up 4dB. This is to keep the signal at the original level, and make the soft parts louder. Everything that doesn't light the gain reduction meter will now be 4dB louder. Including noise.

[chessrock]

As Bluebear and some of the others pointed out . . .

you just need to think of volume in relative terms rather than absolute.

By bringing down or compressing the loud parts . . . you are, in effect bringing up the soft parts. When a signal is compressed don't think of it as lowering the volume of the loud parts. Think of it as lowering (narrowing) the difference between the louder parts and the softer parts.

Sorry if I'm being redundant, but once you really wrap yourself around that one, then the rest of the answers should come to you naturally.