Understanding Dynamic Processors (Compression)

jaysummers75

Jay Summers
there is the apocryphal story (I've been hearing this one in many variations for about 30 years) of an LA based engineer in the 1970's who would walk into a mix session with a rack case full of compressors (enough to apply to every track of a 48 track (2x 24 track machines time-code locked)) patch into the facilities desk and then proceed to provide a final mix in 3 hours - an example of a compressor on every track but there is nothing in this story to tell us exactly how each compressor was applied, if applied at all

in those days compression was used to compensate for factors beyond the medium

today, your sounds are more than likely pre-compressed (they have been developed and shaped using compression and other techniques such as eq) and so do not require further treatment beyond making them sit in the mix which is more about level balancing than it is about compression or eq or anything else

in addition, unless you are working with live audio, you have other tools that you can use before considering compression:

MIDI velocity:
  • can be scaled in most daws to other values,
  • you can randomise them if you are so inclined to give the track some air,
  • you can add emphasis on specific positions within the bar if you are so inclined or
  • take emphasis away in the same manner

if it is live audio then you need to consider whether an individual track needs compression or not
- there is no short solution to knowing the answer to that question other than suck and see

``````````````````````````````````````````````````````````````````````````````````````````````````````````````````````

Thank you for the feedback, it really helps. I do use mostly live instruments as far as the Guitars/Bass, but the Drums don't seem to really have the punch they should. I hear them in the mix and then sound kind of.. just dull. I guess I am having trouble specifically with them.

I use Abletone Live 9, and it usually used for "Dance/House" music, but I used Superior Drummer 2.0 (Which I heard was really good drum software, and I know I can't beat an actual real set, but this is all I could afford.) In Ableton there are samples there, and they just sound amazing. They are audio files, so they have already been mixed, and I think that is awesome, but I just wish I could figure out if it is compression that my own drum EQ is missing. That way I could make use of my own percussion in my head, and really make some waves. I suppose I should give you an example of what I mean.

Maybe if you reply and have the time for this lowbie, maybe I could send you a link and give me your impression?

Either way, thanks a lot for your help.

~J
 

jaysummers75

Jay Summers
Limiters are special compressors, the hardest ones. Multiband is also a very powerful approach. Using a Multiband limiter on each individual track during the mix will certainly kill your audio. The dose makes the poison.
Spending your time choosing sounds, or improving arrangements is a better investment than wasting it in setting zillions parameters in audio processing.
My 2 cents.

`````````````````````````````````````````````````````````````````
I have tried just using the Glue compressor, or the compressors in my library, but they don't seem to have much effect. Then I realized, "Hey! I could use a multiband limiter and EQ my tracks along with the compression."

I only use the limiter really in the master track, but I can certainly add life to each group of tracks, (guitars L and R etc...) by adding the multiband and limiter to the group track. I know it seems odd that a beginner like me would try and tackle something as complex as using multiband limiters on his tracks, but I have learned over the years that I am the type of person that has to get in over his head in order to pinpoint where it is that I must actually start. I know, it is weird. I mean, I can understand the concept of compressing a soundwave, and I know it isn't always necessary, and really should used for instruments that I would like to hear have a little more presence in the mix, but I still seem to be missing something useful that they can do to make my drum tracks sound more full... *racks his brain* MAN, if I didn't spend all of my money on my degree in IT/Media, I might actually have gone to recording school. lol. It amazes me that real producers are willing to give me advice such as yourself.

Thank you for taking the time to comment.

~J
 
Last edited:

bandcoach

Zukatoku - Mod Scientist
``````````````````````````````````````````````````````````````````````````````````````````````````````````````````````

Thank you for the feedback, it really helps. I do use mostly live instruments as far as the Guitars/Bass, but the Drums don't seem to really have the punch they should. I hear them in the mix and then sound kind of.. just dull. I guess I am having trouble specifically with them.

I use Abletone Live 9, and it usually used for "Dance/House" music, but I used Superior Drummer 2.0 (Which I heard was really good drum software, and I know I can't beat an actual real set, but this is all I could afford.) In Ableton there are samples there, and they just sound amazing. They are audio files, so they have already been mixed, and I think that is awesome, but I just wish I could figure out if it is compression that my own drum EQ is missing. That way I could make use of my own percussion in my head, and really make some waves. I suppose I should give you an example of what I mean.

Maybe if you reply and have the time for this lowbie, maybe I could send you a link and give me your impression?

Either way, thanks a lot for your help.

~J

just include a link to a wav download - as with most questions of this type audio examples are usually the key to understanding and identifying the issues

audio of treated and untreated sounds is even better as we can then hear what might be being done wrong

ps no such thing as a lowbie just an apprentice/journeyman/master: the responsibility of journeyman and masters is to guide apprentices and teach them the trade to the best of their ability; kind of like like in Karate where if you ask a master to teach you they are obliged to do so
 

jaysummers75

Jay Summers
just include a link to a wav download - as with most questions of this type audio examples are usually the key to understanding and identifying the issues

audio of treated and untreated sounds is even better as we can then hear what might be being done wrong

ps no such thing as a lowbie just an apprentice/journeyman/master: the responsibility of journeyman and masters is to guide apprentices and teach them the trade to the best of their ability; kind of like like in Karate where if you ask a master to teach you they are obliged to do so


https://soundcloud.com/jay-summers-3/graveinmortui2unmic <-----------------is the link to the part of an unmixed WIP. I am running with a bare preset drum set, no compression EQ or anything is added.



https://soundcloud.com/jay-summers-3/graveinmortui2 <------------------This link is to the attempt that I am making at adding EQ/compression to the drums to add effect, and also adding indivudal EQ to the group track on the guitars, and on the bass I have a multiband limiter with EQ, dropping the mid, boosting the lows, and on the master track I have a stereo enchanced master with a multiband compressor/limiter. I have the gain up on both the output and the limiter to 4.5



https://soundcloud.com/jay-summers-3/eternalspirit <----------------THIS track is a finished piece that I did for a short work. It is my best job to date I think. Although, that is up to interpretation. I am really working HARD AT 0:50 to get everything heard in the above recording.

This recording: https://soundcloud.com/jay-summers-3/egyptiansong <-------- was done with drum samples in my library. I wish I could have my Superior 2.0 sound as beautiful and full as they are. I know that comes down the samples the Superior 2.0 library has, but the samples there are really good. It is just that I fail to bring them to the forefront as they are done with the sample I used in the Egyptian song. This is my goal.


I hope you can see all of my errors. I know that I can hear them, I just don't know where to look to fix them. Thank you for the assist.


~J
 
Last edited:

Headtones

New member
Hate to bring this thread up from the grave (even though its only been three months), but this is a great source of information. Thanks.
 

KingT3sa

New member
Very informative article. I'm just starting to get into the world of dynamic processing and I gotta say it's probably more complex then actually making the track. I sort of just go with what feels right. I was wondering if by any chance you could shed some light on multi-band compressor. I read somewhere that you would use it on the drums and it would bring the instruments together. Kind of like glue. I do like you ideology of thinking in shapes, that's one thing I don't do enough of.
 

AL_EN

New member
I was inspired by the EQ thread to write a similar one on dynamic processing (compression, expansion, gates, limiters).

1. What is dynamic processing?

A dynamic processor is something that outputs a signal, where the level of the outgoing signal is based on the level of the incoming signal. In other words, a loud signal coming in will come out differently than a quiet signal coming in.

2. What are the basic types of Dynamic Processors?

Compressors - the most common - the louder the signal is coming in, the less level it provides going out. In a compressor, a target level is set - called the "threshold" - and any signal coming in that exceeds that level will be reduced. The higher the level is above the threshold, the more reduction is done. More on this later.

Expanders - the quieter the signal is coming in, the less level it provides going out. In other words - it makes quiet signals even quieter. Much like a compressor, the threshold is set at a certain level. Any signal that does NOT exceed that threshold is reduced, and the quieter the signal, the more reduction is done.

Limiters - limiters are like super compressors. The idea is to ensure that the level does not exceed the threshold. Because this amount of compression is extreme, a limiter relies on certain functions and design that regular compressors do not have.

Gates - gates are like super expanders. Anything that does not exceed the threshold is reduced to inaudible. Again, because gates are extreme, they often require a slightly different design than a regular expander.



Now - I'll focus primarily on Compression, because that's going to be the most commonly used dynamic processor.

----------------------------------------------------

COMPRESSION

Every signal you hear is compressed. ????? Yes, every signal you hear is compressed.

Bare with me. Imagine you have a rapper in front of a microphone. The rapper raps, you record. You play it back. You haven't used any processing - you're just playing back the raw vocals.

You are listening to a signal that has gone through at bare minimum 3 stages of compression - and more likely than not - it's closer to 6.

The microphone capsule gains tension as the rappers voice pushes it - in other words - it pushes back - and the more the rapper's voice pushes in - the harder the capsule diaphragm pushes back. In other words, the louder the signal hitting the capsule, the more reduction the capsule does to the signal. That's compression! (It's mild compression, but it's still compression).

Along the way through the microphone, you may hit a tube. Tubes have a non-linear response to voltage - the response is quite curved, and also changes the frequency balance of the signal. This is called saturation - which will tend to "round out" a signal, by reducing the loudest peaks. Compression! And before leaving the microphone, the signal may hit a transformer as well, which will saturate in a similar way. (more compression).

The preamp is going to have multiple stages of saturation - and often times, the more gain you give something - the deeper that saturation curve goes. In other words, the more you drive the signal at the preamp, the more compression the signal experiences.

Then the sound has to actual come out the speaker cones. Well, those speaker cones are going to build up tension when pushed further. See where this is going? This is called "cone compression".


Ok - so this is a bit of a simplification - but there's a point here. The point is that "compression" is always part of the signal. Some mics have less of it, some have more - same with speakers, tubes, transformers, etc. And they all do it in different ways. With tubes, people will talk about their saturation curves and THD (total harmonic distortion - or frequency alterations). With mics people will refer to how it "grabs" a sound - or more specifically - the sound's shape. These all add up to really the most important ideas:

Frequency and Shape!

Instead of thinking of a compressor that compresses - think of it as something that changes the shape of a sound. If you start listening for "shape" the mysteries of compression will reveal themselves to you, and fairly quickly.

Setting a compressor is like setting a mold for the signal to fit into. The threshold determines where the compressor starts working, the ratio is how hard it's going to work, the attack is another way of saying how sharp will the transient sound be, and the release is how much tail or sustain do you want to emphasize.

Yikes! Time out!

What the hell is a transient? A transient is a very fast signal - in other words the "attack" of the signal. Drums have transient attacks. Strings have gradually risinng attacks. So the attack control on the compressor is really like saying - how much emphasis on the attack of the signal do you want? Do you want the attack to be really rounded out and diminished? Set the attack low. Do you want the attack to be prominent and stick out? Set the attack high. Of course, this works directly in conjunction with the threshold. Try it yourself, set the threshold low, and the attack short. Suddenly, the attack sound of your snare is gone. Set the threshold low and the attack long. Suddenly the punch of your kick is very round and bouncy. Set the threshold high and the attack short. Now the snare is a little fatter and rounder, and not quite as spikey (but possibly a little duller). Set the threshold high and the attack long - the change is hardly noticeable, the attack is just a little bit "rounder."

How to achieve maximum punch?

There is a thin line between a transient sound, and a sustained sound. A sound that holds for any noticeable amount of time is sustaining. A sound that moves by too quickly to register as it's own moment is transient. But transients can vary in length. A transient can be half a millisecond. It could also be ten milliseconds. And those won't sound the same. A big factor in punch is how long that transient exists. A quick transient sounds "spikey" - but a long transient sounds "punchy." You want to find the point that makes the transeint exist as long as possible before "flattening out" or becoming a sustained sound. Only your ear can tell you where that point is.

Good samples are already shaped to have that kind of impact - and any additional compression may soften that. Of course, punch has a lot to do with frequency as well - but that's for another thread.

Now what about the release? The release is super elusive. It deermines how long it takes for the compressor to let go. If the release is too short for the signal you are going to get a disjointed sound shape which usually results in distortion. If it's too long, your signal never really returns to its natural shape, and you generally lose tone. So the idea is to find a point that emphasizes the sustain (which is where most of the signals tone lives) properly.

Lastly, when the attack and release are set in a way that seem to argue - the compression can become very audible. You either hear the decent or the acent of the signal level. This is called pumping. It's generally annoying, but can sometimes be used an effect.

----------------------------------

So, rather than think of a compressor as something that effects the "level" of a signal. Think of it as something that effects shape. Why? Because level can be controlled with the volume fader more accurately and transparently. A fader doesn't really control shape, unless you are being extremely meticulous. Conversely, compression will always effect the shape of the sound it is working on.

Once you start hearing shape, you will understand compression.


-Matt.
Thanks for this. I now have a less blurry understanding of compression
 

shubharora734

New member
I've been teaching a lot these days - and I started doing mixes where I detail everything I'm hearing and doing in thorough notes - basically for the cats who don't really have the bread to have a whole album mixed, they can take my notes on the one song and apply the same ideas to the other songs. So far I'm getting a positive response.
 
Top