How to set up a compressor (properly)

There is another thread on compression in the Producer forum but I thought I would like to offer some tips on how to set compressors up here in the Techniques forum. I know many people have issues with them and do not fully understand them.

One of the big problems people have with compressors is you have to set the parameters of a compressor in the right order otherwise you will never get it right. Not many know this. Even the YouTube movie that Jose refers to on the other thread fails to mention this.

If you do this you will get much better sounding compression on your tracks or mix busses. Think ARRT. Attack first, then release then ratio then threshold last. Here is how you do it. This works equally well on individual sources as well as busses and final mixes.

Lets set Attack first.

Start by setting the ratio very high, release as fast as it will go. Now feed audio in and lower the threshold until the compressor starts kicking in and you can hear it. Listen to the attack part of the music. The leading edge or attack transient. While the Attack setting is fast the compressor will jump all over the music and literally destroy the front edge of the sound. Slow the attack down slowly so the desired attack transient is achieved. Listen to how even as you start to apply small amounts of attack the music or the transients all come back and start to sound good again.

(Note: People often have the attack setting too fast and the compressor is destroying the attack part of the music. No matter what you do with other parameters the music will always be screwed) Setting the attack is very important for final mixes as well. Too fast and once again the music is destroyed. The ultra fast release lets you hear far more individual attacks than a slower setting.

Now we set Release

Release controls the speed at which the sound glides back after you have punched it away. The idea is to get that speed to become a musical component of the sound. Think how slow can I get it while maintaing some control. The power in a groove is in a slower moving wave. Listen to Release and feel the way it bounces back at you and at some point it will be like a swing.  This time does not necessarily have to relate to quarter notes or the groove in the music so much but an overall release groove.


Next we set Ratio

The idea is to lower the threshold as much as you can without loosing the effects you have created with Attack and Release. The higher the ratio, the smaller the sound is, although it is more controlled. The lower the ratio as in 2:1 it feels like a larger image. The idea is to find a ratio that sounds big but is controlled. Listen to the size and firmness of the sound.

Last we set Threshold

It is desirable to set the threshold so that the compressor is not compressing all the time (Unless that is the effect you want of course) The correct setting will see the dynamic movement coming to rest at special moments. Too low a threshold creates a flat lifeless sound. Permitting the dynamic movement of the sound to come to rest in some quieter moments allows that moment to attain a momentry bigger 1:1 presence and prevents it from rushing towards the listener with unwanted noise. It is bad enough that quiet moments are small without being squashed smaller still due to higher compression ratios. Each time a sound comes up for air it attains a sense of reality a 1:1 ratio.

Makeup gain or output level

Compressors by their very nature are attenuating the signal so the output needs to be put back to where the input signal level was originally. Use the gain reduction indicator to give you some idea. ie if a compressor is providing mainly - 3db of gain reduction for half the time then set the Makeup gain to +3db to get the signal level back up to where it was.

Compressors are not black art or require rocket science. They are simply one of those processors you need to be careful with and have an approach to setting. Using this method above will give you great transperant sounding results. Even cheaper compressors will sound better after doing it this way. And even if you adjust them differently to this method, try it and see how it sounds after. You might be surprised. One of the problems is that you cannot setup a compressor fast and move on like you can with other effects. The compressor takes time to get it sounding right. The moment you insert one you have to be prepared to put the time in to get it right. Don't rush it!

Presets are OUT. They do not factor anything in at all. When you think of the procedure I have proposed here how could a preset know what to do?

Good luck.

I have compiled this from my own experiences and also from the great tips provided by Mike Stavrou. Mike has got one of the best books out on sound engineering you will ever get your hands on. It is called 'Mixing with your Mind' and is available here from this website:

http://www.mixingwithyourmind.com/

Thanks Herb.  The important thing here is the order of the adjustment. I wonder how many people do it that way. Any other order and one could argue you are wasting your time or going around in circles. That is why people have problems adjusting them properly. eg if you have your attack setting too fast then no matter what you do you will get a bad sound because the attack part of the music is destroyed, simple as that.

I have found one of the best times for very fast attack times is when you have them set for limiting and have a fairly high threshold and you want the limiter to jump on any silly volume surges quickly so they don't clip any inputs etc.. This works better on individual sounds as well.  And you don't hear it because as soon as the source is under the threshold again the compressor/limiter has let it go and you dont really hear it.

I work differently....I think in terms of dealing with the energy level first ....then transient and envelope control . I never feel I waste a minute of time either.

    In effect  how can you know to set attack / release times in relation to control...if you aren't crossing the threshold... that seems like a time waster to me. I always set ratio last.

Firstly this approach does apply to compressors that offer the full range of parameter adjustment. With the ones that are much simpler in their operation (and afterall that is not a bad thing) then you obviously don't have the options I have suggested. I am sure you can still get a great sound and I don't blame you for wanting that type of compressor. It just seems to work.

Rbh You simply lower the threshold during step 1 so the compressor is doing its thing. Try it my way and see what comes out. Transients first. They are vital and important. The reason why compressors overcompress is because the transients are being smashed. They are not set right from the start.

droddey You will never get it right. You will just go around in circles and never really obtain the maximum performance your compressor is capable. It certainly is vague. You will never set a compressor correctly during a mastering session that way either. What I am suggesting is a way to avoid that approach. It does not work.

Thanks, Jeff. I'll give your methodology some careful attention.

This approach was aimed at firstly people who are having difficulty with compressors and who have a hard time getting them to sound right.  matt has backed up the approach already by saying he got better results instantly.

And of course there is more than one way but why not start with a methodical approach and then modify it to suit. Nothing to stop you tweaking any of the parameters once you get it in the ball park so to speak. I definately do that.

I used to do it Dean's way too for a while as I am sure many others do, but this is faster as well and is capable of bringing you to a good place with the compressor fairly quickly. You might find that even Pro's alike do something similar in the order etc. And even if they are not using the order they are arriving at a similar sound.

Turning knobs until its right does not cut it for me. It relies too much on luck.

Jeff,
 I enjoy the fact that you took the time to write this up.

 I disagree with some of the technicalities and I work a bit differently.

 For starters I disagree with the premise that a fast attack will destroy the transients... I believe a big ratio is far more likely to *destroy* transients... but of course you are using a big ratio using in step 1(c)... so your practice will tend to reinforce your impression of what happens when you adjust the attack.

 If I was teaching someone how to listen to a compressor I would start with a very fast attack and a medium ratio and slowly reach down to find the threshold while adding some make up gain.

 I had the good fortune to learn to use the very worst sounding compressors out in the field while mixing FOH on systems far too loud to allow for successful solo inspections at the mix position. So it is easy for me to explain that I found it difficult to learn how to feel like the compressor was under control. It doesn't embarrass me to be honest about that... it was a great place to learn.

 If I wanted to fully explain the use of a compressor in this era of DAWs I would demonstrate with a VST like Sonnitus Compressor and use the fantastic visual feedback that a tool like that provides. You can easily see how attack effects the transient and you can see how release effects the pumping or squashing.

 The other thing I would speak about is how attack can be related to tempo and how a suitable attack can be predicted by considering the content your are working on.

 If you are not prepared to predict an attack setting... a visual tool like Sonitus Compressor will be very helpful in learning about tempo and compression settings.

 FWIW, I also own a pair of Purple MC-77 compressors (Urei 1176 copies... very fast attacke) and a Tube Tech CL-1B (mildly fast attack) so I will address my concern from post #4; When I choose to use the La-610 (LA2a style) I have essentially dialed up a slow attack with a content variable release and moved on in the decision making process.

 I think many people start by saying they don't really understand compressors... then they think they have mastered them... and then much later they come to understand that the use of a compressor is a skill that is very hard to master. Personally, I'm still working on getting better at it.

 best regards,
mike

Not a bad starting place. I would say that there are situations where a fast attack is desirable (but not often). I use fairly fast attacks when doing parallel compression on a drum submix. It can bring out the sustain of the snares, etc. Also when the feel between a drummer and bass player aren't real tight, I can sometimes make it sound better if I squash the attack of the bass and delay it by 3-6 ms. This can allow the the kick transient to define the beginning of the bass note. It also sometimes helps to put both the kick and bass through the same bus sharing a single compressor.

I kind of like Izhaki's discussion on compressors in his book. He talks about compressors in terms of micro-dynamics (the shaping of each note, almost like an ADSR envelope) and macro-dynamics where you are trying more to control track balance. Both are legitimate uses for compressors, but not all compressors are equally suited to both tasks.

mike_mccue


I would say that, in most cases, a fast attack is very desirable.

I believe that the instances where one wants to use a slow attack to purposefully let a loud spike sneak thru and then subsequently clamp down on the decay are few and far between, where as using a compressor to compress the spikes at a moderate ratio while ignoring the bulk of the content in such a way that the track sums more easily is a everyday experience.

best regards,
mike

 
I would agree with you.....if snare drums were few and far between.  But they're not.
 
Letting the transient slip through, but using compression to bring out the decay of individual drums is a pretty common.
 
While I don't necessarily go the same route that Jeff does, his explanation of the controls is going to be very helpful to those confused with compressors.  Just getting your head around what all the terminology means is pretty hard at first.  But once you fully understand the terminology and how that relates to what each function actually does.....this is when "knob turning" is completely acceptable.  At that point you're making educated movements instead of flying on a whim and a prayer!

"Letting the transient slip through, but using compression to bring out the decay of individual drums is a pretty common."

Is it possible you mean to bring down the decay?

I sorta like the body of a snare hit so I might just as likely use a fast compressor like a 1176 type to bring up the decay by bringing down the snap... so I can turn it all up... to bring out the decay.

best,
mike

Skull, you made me paranoid... I was thinking... darn mike... I haven't regularly run a compressor on a snare in a long time... am I getting that lazy?

So I typed in "best compressor for snare" in Google and got this page:

http://www.gearslutz.com/...-snare-compressor.html

I stopped reading after the first 1-1/2 pages.

THANKS JIFF! (Aussie for Jeff)
 
I found your post to extremely useful. I feel like it was aimed at me - experienced musician - pitiful engineer. It is amazing how much effort so many well meaning folks put into explaining how a compressor works without telling you how to actually use it. I know how a compressor works intellectually - but everytime I use one I feel like its a shot in the dark.
 
Of course, if I could sit with an experienced engineer for a couple of years, I'm sure I could get the hang of it :)

mgreene

THANKS JIFF! (Aussie for Jeff)
 
I found your post to extremely useful. I feel like it was aimed at me - experienced musician - pitiful engineer. It is amazing how much effort so many well meaning folks put into explaining how a compressor works without telling you how to actually use it. I know how a compressor works intellectually - but everytime I use one I feel like its a shot in the dark.
 
Of course, if I could sit with an experienced engineer for a couple of years, I'm sure I could get the hang of it :)

The thing is though, no one can tell you. This is a fundamental issue that makes for a fairly ironic problem. You won't figure out how to really use it, until you realize why no one can tell you how to really use it. It's not a tool designed to do a specific thing. It's a creative tool, like a guitar or wood lathe. People can tell you how to operate it. But until you build up your own callouses or ruin a lot of pieces of wood, you won't really understand it.
 
If your purpose is to learn, as apposed to finish a song, then probably the best thing to do is sit down with something like a snare drum track that just is banging on 2 and 4 or whatever constantly. Just play with the knobs relentlessly in every combination and see what that does to the sound. That's how you'll really learn it, because the point of learning how to use a compressor is to use it creatively, not to repeat a formula. There will be many ways that that snare can be compressed which might be cool in a given situation. Then try something different, like a strummed guitar part, then a vocal, then a kick drum, then a bass, i.e. things that have very different attack/decay characteristics, because difference attack/decay characteristics of the track being compressed will interact differently with any given attack/decay settings on the compressor.
 
If you do this studiously, you'll learn a LOT in a fairly short period of time. Try radical stuff and try subtle stuff, and listen to the results. When you then listen to commercial tracks, try to hear, oh yeh, they are using a fast attack and fast release on the snare or the room mics. Or they are using heavy compression with a fast attack and medium release on that acoustic guitar part to really even out and soften the attacks, etc...
 

I would say that, in most cases, a fast attack is very desirable.

I thought I was the only one who thought this.  I've read all sorts of compressor "tips" about giving something more "punch" by using a longer attack.  But whenever I have a track that needs more "punch" and I try to use a compressor (or transient shaper) to "punch" it up, it never sounds as good as just re-recording the track in a punchier manner. 

But that probably just highlights my ineptitude at compressor settings.

(low frequencies hate fast attacks, tho...)

Skull, no worries over here... thanks for clarify what you were thinking about.

I'm still trying to create a personal dialog for working with different tempos... every now and then I think of the same way you might set up delay timings... but you have to account for hold time somehow so it is not as simple as just adding your attack and release times. I try to stay aware of how much time I have before I have to get out of the way for the next hit or pulse.

I also enjoy using slow attack times on occasions and lately have been using my hardware compressors to perform into... it seems to inspire a performance style when you can push into the compressor. If I was really slick I would just use them on monitor and then save the real compression for post... but I have been just tracking with them. It is sort of unnecessary to track with a real fast compressor... because you should just turn it down in the input and up in the monitors... and compress later when you mix, but the slow compressors like the LA2A style give you a effect that really does seem to change the way you perform.

FWIW I routinely use a limiter when recording for my day job TV sound work... but that's because there is often no chance for rehearsal or retakes.

best regards,
mike