Alexander,

> what i don't get is people are saying that you should use a -3dB Threshhold for example. <

You are right to be confused because a statement like that is utterly meaningless without knowing how loud the input is! The real issue is how much the compresor is reducing the volume, which is a combination of the threshold setting and the current volume of the incoming material. This is why all compressors have Gain Reduction metering - so you can see how much the level is being reduced.

Following is a brief explanation of compression.

--Ethan

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A compressor or limiter is an automatic volume control that reduces the volume when the input gets too loud. Originally they were used to prevent AM radio transmitters from distorting if the announcer got too close to the mike. Then some creative folks discovered that a compressor can sound cool as an effect on voices and musical instruments.

The primary controls on a compressor are:

Threshold - also called ceiling - This sets the point at which the automatic volume reduction kicks in. Below that volume the compressor does nothing. When the input gets above that level, the compressor reduces the volume automatically to keep the signal from getting much louder.

Attack time - how quickly the volume is reduced when the input exceeds the threshold. If it's too slow, then a short burst of loud music can get through and possibly cause distortion. So when using a compressor as a tool to prevent overload you generally want a very fast attack time. But when used on an electric bass to get a little more punch, 20-50 milliseconds is often good because that lets a little burst of the attack get through before the volume is reduced. So each note has a little extra "definition" but without the full length of the note being too loud.

Release time - how quickly the volume comes back up after being reduced. If it's too fast, you'll hear the volume as it goes up and down. That sound is called "pumping" or "breathing." Sometimes this sound is desirable, but often it is not. It depends on whether you're using the compressor as a tool to prevent overloading, or as an effect to create a cool sound or add more sustain to an instrument. If you don't want to hear the compressor work, set the release time fairly long [one second or more].

Compression ratio - 1:1 does nothing. 2:1 means if the input rises to 2 dB. above the threshold, the compressor will reduce the level by 1 dB. so now it's 1 dB. above. 10:1 means you have to get 10 dB. above the threshold for the output to go up by 1 dB.

Alexander asked ;

“…….what i don't get is people are saying that you should use a -3dB Threshold for example.”

Ethan answered;

…………”a statement like that is utterly meaningless without knowing how loud the input is!”

I think what “people are saying” is referring to you should set the threshold for 3dB reduction. That means the amount of gain reduction applied is 3dB….

Regarding levels, if the gain structure is correct, the all levels recorded in all tracks, in whatever recording medium you are using should be relatively equal. This is one of the basic tenets of recording in multi track. In digital, levels should be averaging around –6dB. In analog (VU), average around –4dB and peaking at +2 or +3dB. Compression sounds best when applied conservatively IMO. A little goes a long way. I favor low ratios 2 to 1 or 4 to 1 and at max 3 or 4 dB of reduction. I like to compress a little going in and a little more at mix. …. Fats
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This is exactly why you practice at what you do....all singers are different...one produces more volume than another...a good rule of thumb as cedar stated is to use as little as possible 'going in'....for a loud singer i would want to basically LIMIT their ability to push the input meters past +2...for a quiet singer i would only use compression to 'even out' the levels of the track...it also matters what medium you record to....digital sounds 'better' slightly compressed while tape has its own ability to naturally compress somewhat any way...and if youre like me when i was doing the tape thing, if it wasnt going on to the tape at +12 it wasnt LOUD ENOUGH!!!....just kidding...okay not really kidding but thats beside the point...also, just because theres a compressor sitting there it doesnt mean you have to use it...your ears will tell the story...sometimes its easier to compress after the track is down....more control...

thx a lot. now i get it :-)
I knew how to use a compressor before but I wasn't sure if i was using it right. so i think I'm just compressing too much at the recording stage...