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What do compressors do and why should you use them? I hear everyone always talk about how you should compress your sounds, but i dont really know why? From what i can tell compressors normalise frequencies?


Anyone want to clarify this?

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I don't know the exact mechanisms of a compressor, but it's mostly used to make something sound more upfront, it's very easy to understand once you've figured it out.


You mainly use it on percussive stuff to give them more punch. If your sound is too silent and seems somehow not to fit in the mix, apply some compression, it will sound much crispier than just turning up the volume.

or its used on some of basslines (especially the full-on type), to give them more "aggressiveness"... you dont have to use compressors, a track can sound really nice without any compression, I actually use it quite rarely.

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u can use compressors for two things:

- to make a sound fatter, give it more punch as cybernetika said...

- to make levels more even for a sound...

i 'll give u an example. let's say u have this lead in ur track where u want to turn the filter cuttoff way up... chances are when the filter goes up the level will also go way up.. so u can set a compressor to avoid clipping and to make sure that the levels won't be so drastically different after u do ur filter tweak...

hope that made sense...

try to learn what each setting does on the compressor, and don't overuse it...

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They have nothing to do with frequencies.

It's about normalising the amplitude you could say though.

Basically you divide the amplitude values above the threshold value by the value set by the ratio.

Say you have the threshold at 50Db and the ratio at 1:2.

That means that the amplitude of a sound coming in at 90 Db will be brought down to 70Db.

Basically the part of the amplitude scale above the threshold will be halfed with a ratio of 1:2, ie 90Db=40Db more than 50Db, hence the resulting 70Db.


So what you do in simple terms is to make the sound have a lower dynamic range to make it more controlled, and hence being possible to bring up more in level without clipping.


But I would not say that you "should compress your sounds".

At least not if you don't know why you are doing it.

Some sounds might be to varying in amplitude and can't be made loud enough without causing clipping.

If you cannot get the sound to be more controlled by altering velocity or by tweaking the synth, then the compressor is the tool to use to fix them.


And it of course have it's creative uses for some things as well.


But it's by no means generally neccessary to compress things to make them sound good.

From what I noticed it seems more common that people make bad mixes by using compressors far to much.

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Thanks guys thats really shed some light on the subject. I think i understand them now. I havnt used compressors in the past becuase i didnt understand them. Ive got a good idea now as to when they should be used and how. Thanks for the info.

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Thanks guys thats really shed some light on the subject. I think i understand them now. I havnt used compressors in the past becuase i didnt understand them. Ive got a good idea now as to when they should be used and how. Thanks for the info.


If you ad a little compression to your final mix, longer release times equal a more pumping track.

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Maybe im a madman here but,


The simplest way to explain what compression is typically used for would be to say.....

It makes the loud noises softer and the soft noises louder.

Many producers like using compression on the finally mix to get the whole tracks amplitude normal without any clips or spikes from single tracks that would adversely affect this process <normalizing>. Psy guys like it for kicks and bass, all the people out there complaining about their bass and kicks not having enough punch should play around with compressors. dont forget to try some compression on your mastering too though... it might change your sound... for the better.... <snickering>



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  • 2 weeks later...

To add to whats already been said, you can basically think of a compressor as an automatic volume control.


By using the threshold control, you decide at what stage of the loudness the compressor should start to work.


By using the attack control, you allow none, some, or lots of the sound to 'come through' before the compressor starts to work. If you choose an attack time of, say 60ms on a kick drum or bassline or any percussive sound then you'll have a more prominent attack.


By using the ratio, as already mentioned in previous posts, you decide by how much the volume gets reduced by, one it reaches the threshold you've set - 2:1 subtle, 5:1 moderate, 10:1 lots - at this ration the compressor starts to act as a limiter, and stops sound from exceeding the threshold totally. But sometimes compressors can't react fast enough, so a dedicated limiter might be needed for this type of 'job'.


By using the release control you allow the compressor to 'let go' of its volume reduction.


By using the make up control, you can increase the gain of the overall signal after it has run through the other controls, ie, once it has been compressed, you can increase the level because the 'loud parts' have been 'brought down'in volume, relative to the quiet parts.


So what this last stage means, is that you can use compression to reveal 'inner detail' in a sound or mix - if the louder parts are reduced, the overall sound becomes quieter. By using the make up/gain, you boost the overall level of the signal including the quieter parts.


BUT this can also boost any noise in your sound.

AND as said, compression can really destroy a mix. I listen back to my earlier stuff, and although the sound programming and sequence is okay, I've really damaged the 'life' of the recording - some individual tracks have no life, the overall level is very constant and very boring/irritating.


Beware, bad compression technique does more harm than good. I know!!


PS you can also use compression to make your sounds thicker. I don't want to use the word 'punchy' but used carefully it can make the impact of the initial transients of your sounds more... impactful?!


For a full guide to basic compression techniques, search the Sound on Sound articles for Basic Compression Techniques. There's tons of info over there.





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ok some more compression basics:


Reason has a very good compressor.[Not really,a bit outdated but anywayz.] And in Reason 2 it works even better. Compression can really be the difference in a good track and a fantastic track. It is useful to maintain smooth and even levels or it can be used as a creative sound sculping tool. I'll explain the principle's of compression in this tutorial and give you some example settings to work with.

A compressor has 4 controls with wich you can control the way the compressor works. The following controls are on it:












The ratio sets the amount of compression that is being applied when the treshold level is being reached. The settings are set in ratio's like 8:1.

When there is 8db of signal going over the treshold level this will be reduced to 1db when using this setting. So 8db over the treshold level becomes 1db over the treshold level.

The ratio is very important coss it sets the power of the compressor. If you want to use the compressor as a limiter you should set the ratio to full. Preferably infinite:1 but since the Reason compressor doesn't have this setting 16:1 will do. This will prevent most incoming signals to get past the treshold level.



This is the level at wich compression will set in. If a signal doesn't pass this level the compressor won't touch it. But if it does exceed the treshold level compression with the power of the ratio will be applied.



The attack sets the time it takes for the compressor to set in after the treshold level has been reached. If this is set to 0 the compressor will directly work when any signal is passing the treshold level. But if set higher it will gradually set in after the treshold level has been reached. This is useful if you want to maintain the initial attack of the sound you are compressing.



The release sets the time it takes for the signal to get back to it's original level after it has dropped below the treshold level.

If you want to have your compressor to pump up your sound you need to set a fast release. Now pull down your treshold untill you reach the desired effect without clipping. If you haven't reached the amount of 'pump' you like but the signal is already clipping you should set your ratio higher. In this case you could also set your attack faster to get to the loud unprocessed attack earlier.

On the Reason compressor there's also a gain reduction meter on wich you can see how many db reduction you have. If this is to high you have the chance of noise getting to loud and you will definately have no dynamics anymore in your sound.


The Reason compressor is equiped with a make up gain wich makes sure that the ouput level of the compressor is being raised when this is to low.

Compression is really important in a composition. It's not for nothing that all the big studio's have racks full of these devices. It's also advisable to add compression to all your devices actually. Not only will you have full control over levels but the sounds will be also better to mix together.

When you are using a compressor to even out your final mix you better not use extreme settings coss this will result in parts that should be in a low volume to rise and parts that should be loud to drop. You should search for a balance between those two. When compressing a mix there are certain to look out for. When you set your treshold level below the level of you bassdrum this will cause the bassdrum to make the rest of the mix also softer. So you can imagine what will happen then. After each kick the mix will drop resulting in a weird sounding bouncing situation wich nobody would wish for to happen with his track. So you have to make sure that the treshold level is set above the level of your bassdrum.

And this goes for all sounds actualy. If they appear regularly in your mix then the treshold level can't be set under that level or otherwise that sound will control the compressor leaving the mix to be pulled down in volume.


The best way to compress the final mix in Reason is to add it to the output of a mixer and then make another mixer to connect the ouput of the compressor to. That way you still have control over the level wich the compressor produces after compressing.

What you would really need is a pair of main stereo bus inserts but these are not available on the mixer so this will give similar results.

Compression is a process that should be used wisely coss it can make sounds better but, it can also make sounds worse.


Here are some settings wich can make sounds nicer. Note that these sttings are a guideline and must still be tweaked to suit your sounds perfectly.





Ratio: 105


Treshold: 85


Attack: 20


Release: 40





Ratio: 105


Treshold: 80


Attack: 30


Release: 20





Ratio: 103


Treshold: 40


Attack: 35


Release: 60


When you use a compressor you should try various settings because every sound is different, and thus needs different compressor settings. These settings are however nice guidelines wich will help you in the right direction. :)

Compression is one of the few concept that many younger electronic artist have trouble coming to grips with. This article is a follow-up to Dave's wonderful article on basic concepts of an audio compressor. In this tutorial I shall touch upon some of the finer points of uses for compressors. Before I get down to the nitty gritty, I must make one disclaimer: all of this information isn't the matter-of-fact way to compress, but mearly a push in the right direction. An artist friend of mine once said, "Hearing is believing". This saying holds true to using compressors in Reason, mixing with hardware, or on any other digital audio workstation.


Shaping sound with compressors

If music was an ice sculpture, then think of compressors as the chain-saw used to carve the ice. Using the "attack" and "release" setting can be a great way to make a snare punchier or a bassline smoother. One would think that in order to make a sound punchier, that you would set the a fast "attack" setting to achieve that sound. Actually, its the other way around. It breaks down like this:



Punchier/Aggressive sound: slow 'attack', fast 'release'



Smoother/Gentler sound: fast 'attack', slow 'release'



EQ before compressor, or compressor before EQ?

One of the constant questions I get is where to put the EQ and the compressor in the chain of signal flow. To be honest its really a matter of opinion, when it comes to this subject. If you place the EQ before the compressor, then your gonna be compressing your EQed signal. Usually this is the way I patch it up, in reason, because I'll EQ out the sounds I don't want then use the compressor to boost the signal of the sound that I desire. Then again placing the EQ after the compressor might be somewhat useful if your using multiple compressors. Which brings me to my next subject matter below.


A whole lotta compression going on

Is one compressor really enough? It all depends on who you ask. Compressors can be used to not only shape sounds, but make them a bit louder. Most compressors have an input and an output gain. The trick is that you use one compressor to boost your sound's level, then another compressor to shape the sound, then finally another compressor to level everything out. Its pretty much like a train, once compressors connects to another in order to get the sound to where you want it placed in the mix. I shall warn you though, that this method can bring your CPU to its knees, if you don't bounce/sub-mix down your audio tracks. After bouncing down the tracks, normally I just run the rendered audio thru another step of compression to even out the rendered audio.


As I stated before, all this information is to help you build the foundations of a solid track. The only true way to know if your doing your compression correctly is to simply A/B your mix on many different monitors and speakers. If your mix sounds pretty damn good out of crappy, little speakers then your heading in the right direction, with using compressors.

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I find compression to be most important in your final mastering. After your track is layed out, go back and figure out what needs to come more to the forefront of the track.


A quick "Multicompressor" on a finished mixdown is very useful as well. Isolate your three basic EQ bands, and individually compress them to give them a good overall mix. I suck at tutorials, just play around with different settings to get the sound you're looking for.

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