Compressor Attack Time - The Myth...and the Truth! - Tutorial

This video talks about the true meaning of a compressor's attack time - as referenced in Episode 78 of the podcast.
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[@natehoward2916]

This video is amazing! I was having trouble wrapping my head around how the attack time functions. Your explanation along with the visual is excellent! Off to watch your release time video.

[@nickhindman]

The visual wave forms in this and numerous other of your videos are really helpful; your presentations are truly one-of-a-kind.

[@RobotMowerTricks]

An article described it this way and it made so much more sense. I don't remember which website it was but it said something like "The time it takes to reach full compression ratio" . And then I think it said adjustment was adjusting the curve. I think the attack time descriptions should include the word "accelerate" and "curve" to avoid the very common misunderstandings/mythes that you give examples of in the video. I hit thumbs up on this video!

[@zerosynthz]

You are right about attack and release taking the specific time with a slope to get to full GR or to fully stop compressing, but the rabbit whole goes deeper. The milliseconds are not the same in every compressor, try it and you'll see they vary; cause they use milliseconds as a easy reference for users, but is not accurate. That's why some compressors just use terms like "slow", "fast" but no milliseconds at all.

[@RecordingLounge]

This is very true ^^^^^ for a digital compressor, sure, the numbers are probably right. But for anything analog or analog modeled… all bets are off

[@TheCHRISCaPWN]

Thanks. This is a very good visual to drive the point home on what really happens with compressors, and their settings.

[@sentientmlem727]

Love this channel. Great discovery!

[@vadimk4310]

wow. thanks so much

[@ltmillerII]

Excellent. Very informative

[@stupidusername38]

hey Kindle, really good video, it has changed the way i think about attack. I have a question, if the compressor kicks in and reduces the volume by the ratio and reduces the volume below the threshold does the compressor implement its release and stop compressing? Or does the compressor only stop compressing when the audio fades and loses volume until its below the threshold or is it a combo of both scenarios that i've described?

[@RecordingLounge]

Short answer: if the audio is above the threshold, the compressor is in a constant state of attacking-releasing-attacking-releasing. Almost like a trampoline. The audio pushes against the compressor and it pushes back. It doesn’t have to go below the threshold before it releases.

[@Lothyde]

my compressor's attack time triggers before the volume changing by looking ahead

[@RecordingLounge]

Yes for many digital compressors that is true

[@johndc7446]

So in summary if I am not mistaken, the smaller signals that are suppose to be well bellow the threshold should also expect to be affected by the compressor due to the release function? At first I thought that quite signals below the threshold should not expect to be affected by the compressor but this tutorial says otherwise.

[@RecordingLounge]

They will be affected by the release to some small Degree but they won’t trigger the compressor.

[@johndc7446]

@@RecordingLounge I think I am getting the hang of it already. Thanks man.

[@johndc7446]

@@RecordingLounge I would like to ask a last question if you don't mind. How much will the compressor determine to subtract to the signal that is below the threshold? When it is above the threshold and the compression ratio is lets say 10:1; the compressor will only output 1 out of 10 of the levels above the threshold. But how would it calculate the subtraction in the levels below the threshold this time?

[@RecordingLounge]

In a way, yes. It’s based around the gain reduction and the incoming signal. So if you quickly transition from a loud sound (say a transient) to a quiet sound (say the ring of a snare) the compressor will still be “down” momentarily while it tries to release. But in theory if you have a constant signal above the threshold, it won’t affect anything below the threshold because... well basically nothing is below the theshold.

[@RecordingLounge]

I’m sure there’s a way to express it as an equation or ratio of some sort, given certain parameters. I’d just have to think about that. 🤔

[@neddam6663]

I can't find the video of the episode 78

[@RecordingLounge]

I’ve got a handful of videos about compression on my channel, I don’t know if it actually ended up being 1 single video

[@neddam6663]

@@RecordingLounge man, I just listen to your podcast, don't get me wrong but there are things that you didn't explain and are very important, I got a little disappointed with the video, I wanna know more about the release because there are a lot of myths about compression, release don't start when the signal crosses downwards the threshold, that's a myth too and you didn't mention it, you didn't explain what happen when the signal crosses and the attack phase starts happening and then the signal crosses down . What happen then with the compression? The compressor still working? The attack keep developing? And if that's that why? And what happens after that? The release starts right after the attack time reaches the maximum compression level that it's only two thirds of the real compression cuz the compressors are not perfect and give us just an approximation) ok , what happens when the signal crosses the threshold in the release phase? Does the compressor keeps doing the release or the attack starts again? And if that's that when does it start? Right from the begining or right where the release left the compression reason? That what I wanna know, not just basic stuff, I wanted to watch your video because you where right about the time in the attack that indicates the speed , attack is how fast the ratio will start compression from 1:1 to whatever was assigned to be . So if you know all that stuff let me know please, cheers

[@RecordingLounge]

@@neddam6663 I have a video about release time too where I discuss this. kzbin.info/www/bejne/kGSoZYtqfr6EirM You should also know that the "two thirds" figure is also not true for EVERY compressor out there. It is true for some of them, but not all of them. Many, many digital compressors are not this way. Every compressor is slightly different, especially in the analog domain. Some compressors have multiple stages of release, like the LA2A. The LA2A release time is 0.06 seconds for 50% release, then 0.5 to 5 seconds for complete release depending upon the amount of previous reduction. That's straight from the manual. So don't assume that every compressor follows that "two thirds" rule for release or for attack. The short answer is basically this: if the signal is over the threshold, it's constantly attacking and releasing, back and forth, back and forth. Think of this like electricity lighting up a lightbulb. Imagine you ran an electrical signal into a lightbulb that resembled a drum beat. High voltage and low voltage, back and forth. What would happen is the lightbulb would get brighter, then dimmer, brighter, dimmer, back and forth, back and forth. Once the voltage got TOO LOW, it wouldn't lightbulb at all. This is basically how optical compressors work! I also kinda look at compression like a balloon - if you press down on a balloon with your hand (attacking) it compresses, but the pressure inside tries to push back (release) to its original shape. If you tried to balance on the balloon (constantly compressing / over the threshold) it would be a tricky balancing act of your body weight constantly bouncing on the balloon (Attacking, and releasing). The compressor basically knows how to do two things - attack, and release. So it's either attacking, or it's releasing. Hopefully I explained some things. One of the best ways to learn about compression is to try out some of the tests like I have here in my videos. It's a hard thing to explain and it's hard to read about, so definitely try it out for yourself and you may answer all the questions you have. Good luck!

[@neddam6663]

@@RecordingLounge man you don't know how much I appreciate this information, thank you so much because it gave me the answers that I can't find anywhere, I want to know more about that so that I can understand deeply how compressors work so if you could make a video explaining all that technical stuff or if I could speak with you bya private messages o I don't know let me know, I need someone like you to explain me because I have no one that knows how it really works everybody just use compressors without even knowing what they're doing and they explain wrong, some of them just say that they just roll around the knobs until they like the sound and I don't wanna do that, I want to understand what I'm doing, so if you could recommend me a book that explains that, because even the books that I have read theyre all wrong, it seams like it's a conspiracy to not explain things so we don't learn so we can't do things on our own and need to pay a professional to do it. So help me if you can, I'm frustrated, I don't know where to find information, and I don really know how to even formulate the right questions. Thank you very much ✌️

[@todosvuelan6943]

Thanks man, another myth down

[@awedee.0]

RMS too??

[@BodinhoDE]

Your definition of attack and release time is not correct, or at least not precise. The attack and release time are relevant for each increase or decrease of the input volume. It is the reaction time of the compressor to volume changes. attack time: how fast to react to increase of input volume release time: how fast to react to decrease of input volume As long as the signal is below the threshold these times (or rates) are simply irrelevant because it would be the transition time from zero gain reduction to zero gain reduction. The input volume crossing the threshold (upwards or downwards) is only a special case of increase or decrease of the input volume.

[@RecordingLounge]

I don’t think we view it differently ... Your wording is just another way to look at it.

[@BodinhoDE]

Ok, maybe I should not have said "not correct", but I think the definition can be misleading as it only touches the special case of the volume crossing the threshold. You define release as: "Once the audio goes below the threshold how long does it take back up to normal volume." One could infer that the release time does not play a role as long the volume does not fall below the threshold which is not true. The release time determines the reaction time to a decrease of input volume when the input volume stays above the threshold, too (the same goes for the attack for an increase of input volume).

[@RecordingLounge]

I agree with you - did you see my other video on compressor release time? That’s where I clarify the release a little bit more.

[@RecordingLounge]

Compressor Release Time "Myth" - The Whole Storykzbin.info/www/bejne/kGSoZYtqfr6EirM

[@BodinhoDE]

Haha, ok, I see you already covered that. :)

[@pericasuran8640]

Nice video, but not 100% correct! Attack 10 ms (e.g.) doesn't mean that needed gain reduction will be achieved in 10 ms. Example: Signal peaks at 100 dB, threshold set at 50 dB, ratio at 2:1, attack at 10 ms. By the logic presented in the video, we would get 50 dB of gain reduction in 10 ms? But this doesn't happen in reality. To understand what really happens, we need one more factor which is "invisible". Each compressor has something which I call the "gain reduction constant" (because I forgot the actual term :) ). If our compressor has this constant built in at (e.g.) 20 dB - this means that the attack time determines the time in which this "constant amount" of GR can be achieved. In my above example, since we need 50 dB of gain reduction, the constant is 20 dB, attack time is 10 ms, this means that we need "two and a half" attack periods to achieve the necessary 50 dB of gain reduction. In this case 25 ms!! If you don't believe me, test it :)

[@RecordingLounge]

While I do find your comment interesting, and while I AGREE that every compressor reacts differently and is not always exactly what the math says it should be, I should point out -- either your math is incorrect, or your comment is misleading... If we have a 50dB threshold, and a 100dB signal, and a 2:1 ratio., the signal will be going over 50dB., which means the compressor will only let 25dB pass, so the signal would be -25dB of reduction in 10ms. So...I suppose technically 2.5x this would be 25ms...but I don't see how that's relevant, considering the compressor doesn't continue compressing on its own after the gain reduction has been reached (given a constant input signal like a sine wave). Maybe I'm misunderstanding your comment... If we "need" 50dB of gain reduction on a signal that goes over the threshold by 50dB, the only way to do that is with an brickwall limiter. For example, if we are going over the threshold by 50dB, and we have a 50:1 ratio compressor, that STILL will let 1dB go to the output, so we'd be sitting at 51dB. If we had a 100:1 ratio, we'd still be sitting at 50.5dB. It's asymptotic--it never fully reaches "50" in this case, unless you use a brickwall limiter. Now, let's propose a different example, since we're talking about ATTACK time, not gain reduction values. In general, most compressors operate exactly how I described in the video. If our attack time is 10ms, it takes 10ms to reach 80-100% of full gain reduction. Like I said, every compressor is a little different and may not be up to spec, and also, the controls may just be labeled poorly (like on many vintage units). Take a sine wave with a digital compressor and set the threshold to -20dBFS and put a test tone at -10dBFS, and put the ratio at 2:1. Since we're going over the threshold by 10dB, and we have a 2:1 ratio, our output SHOULD yield -15dBFS. Record the sine wave back through and print it on a track. Find a compressor where you can set the attack to something slow like 100ms. Let it play for a few seconds, record it, and print the resulting waveform. You should be able to see visually in your DAW that, after 100ms, the signal drops by 5dB, down to -15dBFS. If you don't believe ME, you can test it, or if you'd rather, I will make another youtube video to prove it. ;)

[@pericasuran8640]

Hi :) Oops, you are correct, it was a lapsus on my part. If threshold is at 50, peak at 100, and ratio 2:1, then GR is 25. It's late, even simple math doesn't compute any more :) But I still stand behind the actual point, which is - attack time doesn't determine the time in which max gain reduction will be achieved. It determines the RATE of GR. Yes, the actual rate of attenuation can be linear or logarithmic or linked to the ratio or to the moon phases or whatever :) Manufacturers are free to do whatever they want, of course, that's why we have so many different comp flavors. But my main logic still stands. Anyway, Think about it, if our compressor were to follow your rules... This means that the RATE of compression (speed of GR needle movement) would need to be different depending on what is the max GR necessary. But how does the compressor know what is the max GR necessary? Does it have a time machine? :) And no, lookahead is not the answer. So while it may SEEM so that the compressor is quick to reach the necessary GR because of possible logarithmic attenuation rates used, the link between the attack time and GR is not as simple as you described. Waiting for the video :P (Just make sure you make examples where you have a nice amount of GR, and the only thing that changes between examples is the attack time)

[@johnchase8510]

+Perica, I think the term you are looking for, is "Time Constant". On some compressors, like Vari Mu, there are settings where the constant is programme dependent. Frequency content will effect attack and release times. Try these experiments with a digital compressor that does not emulate anything to see more accurate representations of time values. When modeling hardware, who knows how up to spec the internals are?