compression attack release

[read]

hi

i understand attack is how fast the signal over the threshold is lowered down by the ratio set.

RELEASE is where i'm confused.

First of all my release setting starts at 50ms.

I don't understand this.

Also....what if i have attack 70ms and release 50ms...what happens then?

[mibo1022]

Release determines the amount of time before the compressor disengages after the signal drops below the threshold. So as for your theoretical, the comp would kick in 70ms after the signal reaches the threshold and would release 50ms after the signal drops below the threshold. The attack "timer" starts before the release "timer" which is how you are able to have your release longer than your attack.

I don't always word things the best, so I hope this makes sense.

[read]

thank you thats great i understand better now

[DVDdoug]

Also....what if i have attack 70ms and release 50ms...what happens then?

If you have a transient that lasts for less than 70mS, maybe nothing, or maybe a slight compression effect.

Otherwise it should work "as expected". Compression should have fully kicked-in* 70mS after the signal goes above the threshold and gain/levels should be back to normal 50mS after the signal falls below the threshold.



As far as I know, there is no industry standard for attack & release times... But it might be about 90%, so at the after 70mS you might have 90% of the compression ratio.

[read]

ok i see

one last question

when i put the ratio infinite to 1, attack instant

and threshold -36DB

why do i still hear sound coming through? I thought that would kill the sound completely

how many DB should threshold be so that no sound would come through?

[mibo1022]

Hmmm...Interesting question. I'm not sure. Just out of curiosity, why would you want it to kill the sound completely? Or are you like me, and just need to know because you just need to know?

[read]

Originally Posted by mibo1022

Hmmm...Interesting question. I'm not sure. Just out of curiosity, why would you want it to kill the sound completely? Or are you like me, and just need to know because you just need to know?

yes out of curiosity

[bezusheist]

Originally Posted by read

how many DB should threshold be so that no sound would come through?

-inf dBFS

[read]

Originally Posted by bezusheist

-inf dBFS

hmmmmmmm

[Lokasenna]

Two things:

1. ReaComp is technically "broken", in that even an infinite ratio still lets a small bit of audio through above the threshold. Most compressors/limiters will cut it off properly though.

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.

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.

As to your original example, with Attack @ 70ms and Release @ 50ms:

- The signal comes up past the threshold.

- The compressor immediately starts compressing a tiny bit.

- Over the next 70ms, the compressor will compress more and more until it hits 3:1 or whatever you've set.

- When the signal drops off, the compressor will spend the next 50ms compressing less and less until it stops compressing entirely.

- If the signal drops below the threshold before the attack time has elapsed, (I think) the compressor will say "alright, I'm at 50% of my maximum compression" and swap over to the appropriate position in the release curve.

[slipstick]

Originally Posted by read

hmmmmmmm

The compressor simply lets through everything below the threshold without modifying it. If you want it to let nothing through you would need the threshold at -infinity.

Steve

[timlloyd]

Originally Posted by read

ok i see

one last question

when i put the ratio infinite to 1, attack instant

and threshold -36DB

why do i still hear sound coming through? I thought that would kill the sound completely

how many DB should threshold be so that no sound would come through?

In your scenario the output signal should be equal to the Threshold: -36 dBFS. It's not quite that simple, because Attack is rarely instant, but that's not super important here.

If you wanted to get silence out, you'd need a compressor with negative ratio (-1:1) so that, instead of 'becoming horizontal' at inf:1 Ratio, the transfer function curves back down to -inf dB above the Threshold.