Compressor Release, Technical Question?

[eternalux]

Hello.

I have noticed on a compressor, The Release function compresses the audio even though the signal drops below the Threshold. But one thing I dont understand is that, when the signal is in the Attack stage everything above the Threshold is being compressed, so when the signal drops below the threshold, into the Release stage, there is another instance of compression... what determines where the Threshold is placed for this specific "Release" compression ?

when a programmer is writing a compressor plugin.. what's happening when the signal drops below the Threshold? Is there any relation between the compression here and the regular Threshold and Ratio ?

here is an image to demonstrate exactly what I'm talking about, pointed out by the arrows.



I'd appreciate any help.

[BertKoor]

The release simply controls how fast the set compression ratio should go back to 1:1 (no compression) when the signal drops below the threshold.

Now what was the question again?

[eternalux]

Hey BertKoor, I appreciate you replying.

The thing is, Ive been reading so much on compressors but no-one ever seems to explain this little bit about the compression that takes place at the Release stage..

I understand that Release is the amount of time for the compression to recover back to no compression.. but the thing that I dont understand is that.. well it's dropping below the Threshold right? But its still compressing in the Release stage.. so does this mean that the Threshold follows the signal down when the signal drops below the Threshold ?

maybe my understanding of how compressors "technically" work is a bit naive.. perhaps to understand this i would need to study the actual functions in the code?

[aud.io]

Blue line: Compression kicks in from none to full.
After that: compression keeps going on as signal still above threshold.
green line: release stage drops compression from full to none (because signal is below threshold).

So the yellow boxes mark the time where compression takes place.

OT: Whats the best free software for quick charts like these please?

[BertKoor]

Maybe this picture clarifies it:


The image is taken from an article on Harmony Central: http://www.harmony-central.com/Effects/ ... mpression/

All that a compressor basically does, is adjust the gain. How much gain is reduced is controlled by the ratio. When to kick in is controlled by the threshold. How fast to react on going from below to above threshold is controlled by the attack. How fast to react on going from above threshold to below threshold is controlled by the release. Some also have a "soft knee" function that smoothes the transition around the threshold point.

[eternalux]

hey thanks to both of you guys for responding.

I think Im starting to understand this better now. thanks again.


about the image.. I made it using the free plugin "s(M)exoscope" I just took away all saturation and leveled the brightness to make the image alot more clear and simple.

[dark_virus]

I'd like someone has shown me this graphs 5 years ago...

[jackson]

Maybe this picture clarifies it:


The image is taken from an article on Harmony Central: http://www.harmony-central.com/Effects/ ... mpression/

All that a compressor basically does, is adjust the gain. How much gain is reduced is controlled by the ratio. When to kick in is controlled by the threshold. How fast to react on going from below to above threshold is controlled by the attack. How fast to react on going from above threshold to below threshold is controlled by the release. Some also have a "soft knee" function that smoothes the transition around the threshold point.

That picture should be the background image in the beginners forum

[SARcazm]

Blue line: Compression kicks in from none to full.
After that: compression keeps going on as signal still above threshold.
green line: release stage drops compression from full to none (because signal is below threshold).

So the yellow boxes mark the time where compression takes place.

OT: Whats the best free software for quick charts like these please?

Amazing and great diagram and explanation. I thought I'd finally figured out compressors, only to see that I'd totally misunderstood the release section! I'd always pictured in my head that the release gradually drops the signal down to the original level, but in fact it's the other way round

For me Aud.io's should be used, not Harmony Central's, as an explanation, as it shows the release stage clearly.

Anyway, this brings up a couple of (re-noobie) questions:

1) what's the point of the release?? All it seems you're doing is making the drop in volume from above/below the threshold more than it was originally. I can see how that empahsizes that point in time, but is there another reason for it?

2) Is this an example of a hard knee?? Can you edit the diagram to show the different knees affect?

Thx for this,

S

[kylen]

1) what's the point of the release?? All it seems you're doing is making the drop in volume from above/below the threshold more than it was originally. I can see how that empahsizes that point in time, but is there another reason for it?

I like this thread too - pretty cool with all the pics and links and clarifying release.

I think that in the picture by aud.io (maybe this is obvious) it shows the input signal dropping below threshold following the attack time which engages the compressor. The compressor remains engaged though and still acts on the input signal (even though it drops below threshold), the compressor will stay engaged (to varying degrees) until release completely (or effectively) lets go.

The picture reminded me of this, sometimes it's easy to forget that the gain reduction (ratio) is applied to any input signal whenever the compressor is engaged (as determined by the detector).

[BertKoor]

1) what's the point of the release?? All it seems you're doing is making the drop in volume from above/below the threshold more than it was originally. I can see how that empahsizes that point in time, but is there another reason for it?

The release can be useful om material where the signals fluctuates between above and below threshold very quickly, e.g. 16th percussive notes. If you set a long enough release time, then it will keep on compressing up until the signal goes above threshold again, so the attack phase is faster or will be skipped. I'm not saying you should do it that way, but the option is there.

2) Is this an example of a hard knee?? Can you edit the diagram to show the different knees affect?

The effect of knee settings can be shown as follows.

Here is a simple signal that gently fades in and out:


Now if that's compressed with a hard knee, you can see the exact points where it goes above and below threshold:


With a soft knee those transitions are smoothened:

[wrack]

Many thanks for this thread!

[kaufi]

If someone wants to know the "basic" about compression, I can recommend the manual from the Kjaerhus GCO-1 compressor (www.kjaerhus.com). It's a very pretty explanation with good graphics! - imho

@LXNDR1: If your compressor isn't fast enough to catch your peaks even with the fastest attack, I would set a GATE befor the Comp. At vocals I do this every time. Sounds more pro, but don't ask me how long it tooks me to found out that ! (almost a year - coincedence)

[Cordelia]

Here's an oversimplified example of creative use of release:
Think of a snare hit as divided into 3 parts- first, the initial whack, second, the body of the snare resonating, and third, the rattle of the snares.
Set the attack at 20-40 ms (not too fast). That means the initial whack gets through unaffected.
The compressor kicks in at the point the drum begins to resonate.
Set the release time so the compressor "turns off" before the snares rattle. The snare rattle will be unaffected by the compressor. The compressor will be acting only on part 2, the drum resonance.
Now, by using the threshold and ratio knobs, you have control over the "volume" of the body resonance of the drum.
Without a release control, you could not tell the compressor to stop, and the snare rattles would be compressed as well.
This is a very smooth way to control an overly resonant snare drum, without having to resort to trying to EQ the resonance out and thereby affecting the tone of the whole drum.

[rbet]

Many thanks for this thread!