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Old 04-20-2017, 11:51 PM   #11
timlloyd
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Join Date: Mar 2010
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Quote:
Originally Posted by Lokasenna View Post
2. Attack time is how long it takes the compressor to reach "full strength", like the time it takes for a car to hit 60mph. It's NOT a measure of how long before the compressor reacts. The amount of gain reduction is ramped up to ratio you've set; the car is moving the whole time.
Technically, Attack time is the time taken for the device to reach some proportion of maximum gain reduction (as determined by the Ratio). This proportion is not constant across all compressor designs, which is one thing that contributes to them sounding and feeling different. As you imply, it begins the instant that the input signal breaches the Threshold.

(Unless you have non-zero Pre-comp in ReaComp, just to muddy the waters a little bit.)

Quote:
Originally Posted by Lokasenna View Post
Likewise, Release time is how long it takes the compressor to completely let off after the signal falls below the threshold. As with Attack, it's a smooth ramp down. Think of it as braking a car - you can slam on the brakes, but it'll still take a few seconds until you stop.
This isn't correct. Release, much like Attack, is the time taken to restore (some proportion of) the reduced gain (as determined by the Ratio).

So when do the attack and release phases happen?

They both happen while the signal is above the threshold, so the easiest way to think about it is:
- increasing gain reduction meter = attack phase
- decreasing gain reduction meter = release phase

It's easy to prove this to yourself. Just set up ReaComp on a drum bus with 2:1 Ratio, very low Threshold so it's buried in compression constantly. Now play around with the Attack and Release controls. If the commonly repeated definitions of Attack and Release were correct, neither control would do anything in this scenario, because the input signal is always above the Threshold ... but of course they do

This is a great way of learning how to use these controls more effectively, and how to hear what they're doing with less extreme amounts of compression. It's probably easiest to hear with drums, but by all means do the same thing with other sources too

(Source: I work for an audio plug-in company; not a developer, but close enough to the design process that I know what's going on under the hood. There's also a good write up from another plug-in designer here)
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