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Old 04-22-2017, 11:24 AM   #22
ashcat_lt
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Join Date: Dec 2012
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Quote:
Originally Posted by mibo1022 View Post
I did read your posts above. And your explanation of attack and release are fairly clear to me. I'm still a little confused about knee though. So is it that attack and release are a ramp up based on time, whereas knee is based on how far above the threshold the signal is regardless of how long it takes to get to any particular level? Is this correct?
Yeah, the knee is about the target gain reduction based on where the detector level is relation to the threshold. It is essentially a modifier to the ratio, and has nothing to do with time whatsover.

The compressor decides what gain reduction it should be applying based on threshold, ratio, and knee, and then starts trying to get there. How long it takes to get there is up to attack and/or release. In normal usage, a compressor is almost never actually applying as much gain reduction as it should because the level is always changing, and both attack and release are always smearing it's reaction time.

...and that's without even starting to talk about RMS window or pre-comp.

Since we're talking about knee, it's important to realize that it "spreads" around the threshold. That is, some signals below the threshold will be compressed anyway, but it doesn't actually reach full ratio until somewhere above the threshold.

An unfortunate side effect of this is that with very high ratios (limiter/clipper function), you end up with outputs louder than the threshold. The gain reduction actually folds back on itself in an unnatural and undesirable way. And that's on top of what was mentioned above about how ReaComp's "infinite" ratio setting is only actually 10000:1. All of that means you can't meaningfully predict the limit level even if all time constants are at 0. If Attack, Release, or RMS time are greater than 0 (or AA/oversampling is turned on), you wouldn't be able to predict that limit anyway, but...
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