Someone explain compression ratio...

[Crayon Boy]

Okay... I have been learning a ton about compression lately and I have a ton of questions. Can someone explain how ratio on a compressor works?? I understand that the attack is how fast the compression kicks in... the release how long the compression holds... the threshhold is where the compression starts to kick in. I understand that the ratio is how much the signal is squashed, but I don't understand much more than that. Is 2:1 more compression than 16:1?? Or vise versa? I have heard it explained that 2:1 squashes the signal in half while 16:1 only squashes it 1/16th. I've also heard that 16:1 means that for every 16db the volume raises above the threshhold only 1db gets by... and that at 2:1 for every 2db above the threshhold only 1db gets by? Also, what does 1:1 do? How about infinite:1? Any info on ratio would be greatly appreciated. Thanks!

 

[Light]

Ratio of input to output. For every x above the threshold on the input it goes up y on the output. So, for instance if the ratio is 4:1, if the input signal goes up 4 dB, the output goes up 1 dB. Similarly, if the input goes up 8 dB, the output goes up 2 dB.


Light

"Cowards can never be moral."
M.K. Gandhi

 

[littledog]

Is 2:1 more compression than 16:1?? Or vise versa?

Visa versa

Originally posted by Crayon Boy
I have heard it explained that 2:1 squashes the signal in half while 16:1 only squashes it 1/16th.

Wrong.

Originally posted by Crayon Boy
I've also heard that 16:1 means that for every 16db the volume raises above the threshhold only 1db gets by... and that at 2:1 for every 2db above the threshhold only 1db gets by?

That's correct, although the way Light describes it is perhaps more precise than "gets by".

Originally posted by Crayon Boy Also, what does 1:1 do? How about infinite:1? Any info on ratio would be greatly appreciated. Thanks!

1:1 doesn't compress at all. However, occasionally a signal will be run through a compressor at 1:1 because the engineer likes the coloration that the circuitry imparts, even without any compression happening. Note: this is usually done with high end boxes, not budget stuff. Infinite:1 would be brickwall limiting. Once the theshold is hit, the signal gets no louder, regardless of the dynamics of the original source.