Could somebody please elaborate what Compressors & Limiters actually do?
- Thread starter Nibblez
- Start date
I wrote this on another thread.
"
I'll try to explain how a compressor works mathematically because words change person to person, language to language, but math is universal.
Lets say you have the following unit-less values representing the volume intensity of a track at a certain point, taken at 5 different times.
12,7,9,11,10
The mean of these numbers is
9.8
The standard deviation is: (standard deviation is the square root of variance which is the square of the difference between each value and the average over the average)
4.1
Now if we were to apply a compressor with the following setting:
-threshold 7
-ratio 4
This is what would happen
12,7,9,11,10
- (7) <- This would be your threshold. We want only values that are above the threshold to be affected.
________________
5,0,2,4,3
5,0,2,4,3
________
4 <- This would be your ratio
=1.25,0,0.5,1,1.33
1.25,0,0.5,1,1.33
+ (7) <- Here we add back the threshold value that we originally subtracted
_________________
8.25,7,7.5,8,8.33
After the compressor has done it's main work this is what you'd be left with for your new volumes:
8.25,7,7.5,8,8.33
The mean of these new numbers is:
7.8
Therefore we will increase the output gain by 2 so we have the same mean as the original.
8.25,7,7.5,8,8.33
+ 2
___________________
10.25,9,9.5,10,10.33
Our final values are:
10.25,9,9.5,10,10.33
now if we take the standard deviation of these new numbers we will get:
1.9
Which is less than the initial S.D of 4.1 meaning that the difference between individual values is now far less.
The higher the ratio, the smaller the standard deviation becomes.
Math is everywhere.
"
Originally posted in: https://www.futureproducers.com/for...nd-what-compressors-do-465378/2/#post49761874
A limiter is a compressor with a ratio between 10 and infinity, most commonly you will find brickwall limiters and they have a ratio of infinity.
"
I'll try to explain how a compressor works mathematically because words change person to person, language to language, but math is universal.
Lets say you have the following unit-less values representing the volume intensity of a track at a certain point, taken at 5 different times.
12,7,9,11,10
The mean of these numbers is
9.8
The standard deviation is: (standard deviation is the square root of variance which is the square of the difference between each value and the average over the average)
4.1
Now if we were to apply a compressor with the following setting:
-threshold 7
-ratio 4
This is what would happen
12,7,9,11,10
- (7) <- This would be your threshold. We want only values that are above the threshold to be affected.
________________
5,0,2,4,3
5,0,2,4,3
________
4 <- This would be your ratio
=1.25,0,0.5,1,1.33
1.25,0,0.5,1,1.33
+ (7) <- Here we add back the threshold value that we originally subtracted
_________________
8.25,7,7.5,8,8.33
After the compressor has done it's main work this is what you'd be left with for your new volumes:
8.25,7,7.5,8,8.33
The mean of these new numbers is:
7.8
Therefore we will increase the output gain by 2 so we have the same mean as the original.
8.25,7,7.5,8,8.33
+ 2
___________________
10.25,9,9.5,10,10.33
Our final values are:
10.25,9,9.5,10,10.33
now if we take the standard deviation of these new numbers we will get:
1.9
Which is less than the initial S.D of 4.1 meaning that the difference between individual values is now far less.
The higher the ratio, the smaller the standard deviation becomes.
Math is everywhere.
"
Originally posted in: https://www.futureproducers.com/for...nd-what-compressors-do-465378/2/#post49761874
A limiter is a compressor with a ratio between 10 and infinity, most commonly you will find brickwall limiters and they have a ratio of infinity.
Last edited:
krushing
Moderator
In a very simplistic way, compressors turn down sounds that exceed a certain loudness (the threshold), by a certain amount (the ratio). The rest of the parameters determine how the turning down is done, how long it lasts and so on. A limiter is simply a compressor that turns the volume down very drastically - the infinite ratio mycbeats mentioned simply means that everything above the threshold gets turned down so it doesn't exceed the threshold. And that's it.
There are a lot of confusing statements about compression, like "compression makes things loud" and "it makes soft parts louder and loud parts softer" but the "regular" type of compression - called downward compression - is simply an automatic volume knob that turns things down (the opposite of this is, unsurprisingly, upwards compression and that simply turns up the quiet end of things but doesn't touch the loud parts). This allows you to turn the whole thing up, and thus making things relatively louder, but compression itself doesn't do that.
There are a lot of confusing statements about compression, like "compression makes things loud" and "it makes soft parts louder and loud parts softer" but the "regular" type of compression - called downward compression - is simply an automatic volume knob that turns things down (the opposite of this is, unsurprisingly, upwards compression and that simply turns up the quiet end of things but doesn't touch the loud parts). This allows you to turn the whole thing up, and thus making things relatively louder, but compression itself doesn't do that.
Man that was confusing...a compressor changes the wave shape and squeezes your mix together by changing the dynamics. And a limiter is an extreme compressor
It doesn't change the shape, it changes one parameter of it, the amplitude of the oscillatory function.
Brickwall limiters do change the shape depending on how hot you approach the ceiling, for example a sine wave would have square wave characteristics where the original amplitude exceeds the ceiling.
I'll try a way simpler, elementary school level mathematical explanation.
two sound level values, 2, 6.
divide them by the ratio, lets say 2
you'll have 1, 3.
add one so that the lower of the values remains the same
2,4,
see how much closer the values are to each other now?
therefore a compressor reduces the difference between the highest and lowest peak in your song (aka dynamic range)
lol yes, but all stock ones (as far as I know) do, mostly the vintage emulations don't.
bandcoach
Zukatoku - Mod Scientist
I would also go one better and suggest that the need for makeup gain is not as much as your explanations might suggest.
Your second explanation also applies the compressor unilaterally, which is unusual, given that we expect a compressor to be applied above a minimum threshold, so a better basic math explanation might be
two values of 2 and 6
our threshold is 4 (everything >= 4 is affected)
the compression ratio is 2:1
divide any value by the left-hand value in the compression ratio
our resulting values are now 2 and 3
we may or may not need to add makeup gain to this situation depending on whether we want to return to the threshold value
i.e. adding makeup gain is a case of judgement, not an automatic pilot choice
Your second explanation also applies the compressor unilaterally, which is unusual, given that we expect a compressor to be applied above a minimum threshold, so a better basic math explanation might be
two values of 2 and 6
our threshold is 4 (everything >= 4 is affected)
the compression ratio is 2:1
divide any value by the left-hand value in the compression ratio
our resulting values are now 2 and 3
we may or may not need to add makeup gain to this situation depending on whether we want to return to the threshold value
i.e. adding makeup gain is a case of judgement, not an automatic pilot choice
B Side Producer
Moderator
I can advice you on macprovideos. They're very comprehensible videos about everything that has to do with music production. That's a good way of getting to know a bit of the basics.
macProVideo.com - Streaming Tutorial-Videos & HD Training Downloads for Audio, Graphics, & Video Editing Software
macProVideo.com - Streaming Tutorial-Videos & HD Training Downloads for Audio, Graphics, & Video Editing Software