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-- Using Compression to add "warmth"
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So mystical ninja, it's perfectly true that a compressor would help "bring out the lows" in vocals if the highs were too loud, i.e. if the chunks of time during which was the vocal was high were louder than the ones during which it was low, since the gain would be decreased on the high parts more than on the low ones. But it is also true, as Sanguis Mortuum said, that in the parts of a song where the compressor lowers the gain, all frequencies are lowered equally.

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All a regular (digital, non-multiband) compressor does is lower the gain when the threshhold loudness is reached.

It doesn't just lower the gain, it only lowers the gain of the signal that is above the threshold. So, if only the high frequencies are passing the threshold, only the high frequencies are compressed, thus all frequencies are not lowered in gain equally.

hi all, first post, so go easy on me...


I'm pretty sure that mystical ninja is right, as that is how it is possible to raise the 'noise floor' or noise underneath the samples through compression. As it chops the tops off your peaks, you can turn up the signal, bringing up the lower level signal that doesnt touch the threshhold , also bringing up with it the 'noise floor'. Hope this makes sense...

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Originally posted by mysticalninja It doesn't just lower the gain, it only lowers the gain of the signal that is above the threshold.

Yes, "signal" meaning the whole stream of audio. A normal compressor does not detect which frequency ranges are passing the threshhold (that's what a multiband compressor does). All it detects is whether the audio signal as a whole is passing the threshhold, and once the signal passes the threshhold, it lowers the gain on the whole signal.

In order apply to gain separately to different frequency ranges, you have to split one signal into two or more signals. A normal compressor does not do this. All it does is detect and control the level of a single audio signal:

"A compressor accomplishes its task of reducing dynamic range by using a variable-gain amplifier to reduce the gain of the signal. This is typically carried out in analog systems by using a voltage controlled amplifier which has its gain reduced as the power of the input signal increases."

http://en.wikipedia.org/wiki/Audio_...ion#Explanation

That is all a normal compressor measures and modulates: the power of a single audio signal. It does not act differently on different frequency bands within the same stretch of time; that's what a multiband compressor is for.

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Most of the compressors we use in music production operate on what is known as the full-band principle, where the entire audio signal is processed via a single gain-control element. When gain reduction occurs, the whole signal level is reduced, just like turning down a volume control. In other words, whenever a loud peak occurs (whatever its frequency content) that forces the compressor to act and the level of the whole signal is reduced until the loud event has passed. A common problem arising from this method of compression is that a loud kick drum (which produces mainly low frequencies), will trigger the compressor and consequently pull down the gain of everything else that happens to be passing through the compressor at the time, even though those other sounds might not need compressing. ... The main advantage of multi-band compression [as opposed to normal, full-band compression] is that a loud event in one frequency band won't trigger gain reduction in the other bands [as it would in normal compression], so when that loud kick drum comes along, instead of pulling the whole mix down with it, only the low-frequency sounds (kick and bass instrument) will be compressed, leaving the mid-range and high frequencies untroubled.

http://www.soundonsound.com/sos/aug...s/multiband.asp

Case closed.

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Originally posted by mysticalninja It doesn't just lower the gain, it only lowers the gain of the signal that is above the threshold. So, if only the high frequencies are passing the threshold, only the high frequencies are compressed, thus all frequencies are not lowered in gain equally.

NO. What you're describing is a multiband compressor. You clearly dont have the slightest clue how a compressor works...

Ah sorry MrBoJangles I confused you.. wrong choice of words on my part.

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Originally posted by Sanguis Mortuum NO. What you're describing is a multiband compressor. You clearly dont have the slightest clue how a compressor works...

Ok, 'only the high frequencies are compressed' is wrong, that is only possible with a multiband compressor, you are correct. What I ment to say, is only the signal above the threshold is reduced in gain, which may happen to only be the high frequencies in a sound, but yes, technically all the frequencies in the signal above the threshold are being reduced.

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Most of the compressors we use in music production operate on what is known as the full-band principle, where the entire audio signal is processed via a single gain-control element. When gain reduction occurs, the whole signal level is reduced, just like turning down a volume control. In other words, whenever a loud peak occurs (whatever its frequency content) that forces the compressor to act and the level of the whole signal is reduced until the loud event has passed.

Yes, the whole signal above the threshold that is. Think about it, if the entire signal was reduced when the threshold is passed, it wouldn't change the dynamics at all, would it?



This is what makes it different from a triggerable volume knob.

This next little gem you quoted proves my point.

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The main advantage of multi-band compression [as opposed to normal, full-band compression] is that a loud event in one frequency band won't trigger gain reduction in the other bands [as it would in normal compression]

In normal compression a single loud event in one frequency will reduce the gain for all signal above the threshold, it does not need to detect frequencies to do this.

Let's say you have two sine waves going on at the same time. One of them, the higher one, goes above the threshhold for a short bit. A normal compressor will reduce the gain on both of the sine waves for as long as the louder wave goes above the threshhold.] When gain reduction is used on a normal compressor, it is used on all frequencies at once. That is the point made in the article I quoted. The author says that, for example, you might have a kick that's above the threshhold. In normal compression, if you have a compressor on the master, everything else that's happening at the same time as the kick will also be reduced in volume: vocals, hi hats, synths, whatever. This is why you get that "pumping" effect if you use too much compression on the master bus. The whole song "pumps" in and out, pulsing with the kick that's causing the compressor to reduce the gain.

Hopefully this is clear now...

Whilst the thread has gone a little off topic, it has been an interesting read. However, I'm glad that Mrjivebojingles has stepped in and explained exactly how a compressor works because this is the same as I have been taught and when Mysticalninja and richg pushed the idea of a compressor only affecting certain frequencies, I began to question if I ever understood a compressor in the first place.

Are we in agreement now that a normal compressor compresses the entire signal, not just the frequency that steps over?

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Originally posted by G-Con Are we in agreement now that a normal compressor compresses the entire signal, not just the frequency that steps over?

Yes we are all in agreement of that.

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Mysticalninja and richg pushed the idea of a compressor only affecting certain frequencies

That's not even close to what we said at all.

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Originally posted by mysticalninja Yes we are all in agreement of that.

Good, thats all that I was trying to say really...it certainly didnt sound like you agreed though with your statements like "So, if only the high frequencies are passing the threshold, only the high frequencies are compressed, thus all frequencies are not lowered in gain equally."...

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Originally posted by Sanguis Mortuum Good, thats all that I was trying to say really...it certainly didnt sound like you agreed though with your statements like "So, if only the high frequencies are passing the threshold, only the high frequencies are compressed, thus all frequencies are not lowered in gain equally."...

I know I really didn't mean to say that.

waves c4 is good, but i prefer the one that comes with cubase.

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Originally posted by newbie dewbie I'm not that familiar with compressors, but what I've noticed is that by bringing up certain frequencies while lowering others, you make the sound more full by making more frequencies easily audible. I've been able to get a more organic and cleaner sound out by compressing. I usually set the threshold pretty low with a ratio no higher than 4:1 and usually soft/medium knee.

Thats not what compressors do. A compressor is an automatic gain reduction tool. So you stick it on a mixer channel and whenever that channel's volume exceeds the compressor's threshold, it reduces the gain. The old analogy is of a mixing engineer watching the meters like a hawk and twatting down the volume slider whenever it goes above a certain point.

The point at which gain reduction starts is the threshold. So if you set a compressor's threshold to -3dB, but the peak signal going into the compressor is lower than that (say -10dB) then the compressor will do absolutely nothing.

When the signal at the input peaks above the threshold then the compressor starts working on all the signal above threshold. The amount of gain reduction that it applies depends on the compression ratio. So if you have a 2:1 ratio the the compressor will limit the gain to 1dB for every 2dB over the threshold you go.

If you had a compression ratio of 10:1 then the compressor will limit the gain to +1dB over the threshold for every 10 dB over the signal goes.

Example:

Threshold = -20dB
Ratio = 10:1
Peak signal going into compressor = 0dB

The compressor will work on every part of the signal over -20dB. The peak signal is 20dB over the threshold. The 10:1 ratio means the peak signal is now -18dB which means that at most, the compressor has applied 18dB of gain reduction on the peak. Thats alot.

Warmth is an onomatopaeic word used to describe something like 'loads of bass'.

Compressors have an output gain stage to compensate for extreme gain reduction that makes the output signal really really quiet. So the idea is to add loads of post gain to make it as loud as (if not) louder than it was before (only with less dynamic range since you lower it by using gain reduction).

This amplification is done by a couple of means. The 2 big ones are listed below:

1) Solid State amplification.
2) Tube amplification.

Both have different distortion characteristics when you overdrive them. When people 'refer' to 'warm' compressors they refer to compressors that most likely have a tube amp gain stage.

People love tubes. But fucking hell are tube compressors expensive. Vintagewarmer is a compressor with an output gain stage that attempts to mimic tube amplification.

Although you could just as well use any compressor and stick a tube amp simulator after it in the signal chain - like TLs Saturated Driver (freware tube amp simulator!). Dont touch the output gain on the compressor. Instead gain up using judicious amounts of TLs.

Edited with example for clarity.

http://download.yousendit.com/326051EF0617967E

Alright enough of this. This is the same kick sample. The only difference is one has a waves c1 compresor on it. Compressors can't change the frequency content of a sound MY ASS.

And you're welcome for the kick sample.

A compressor is an automated gain control. That is all it is. You could, theoretically, get the same result by automating the volume yourself, if you had fine enough control of it in your DAW.

If certain frequencies end up being louder relative to the track as a whole, that's a side effect of the gain of the audio signal being lowered and raised at different points in time where the frequency content happens to be different. But non-multiband compressors do not act directly on specific frequencies or frequency ranges. They just deal with amplitude.

I agree with you, but a compressor does bring up certain frequencies and bring down others depending on the sound source and how you use it, and it has been common for years for engineers to use compression to bring out the click in a kick drum or warm up vocals. That's all I was saying from the begining.

It's clear you both know how compressor works. This is getting quite repetative.

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Originally posted by mysticalninja I agree with you, but a compressor does bring up certain frequencies and bring down others depending on the sound source and how you use it, and it has been common for years for engineers to use compression to bring out the click in a kick drum or warm up vocals. That's all I was saying from the begining.

A compressor doesn't bring up anything and is totally not sensitive to frequency - only the amplitude of a signal. It 'supresses' any part of a signal that exceeds its threshold (doesn't matter what the frequency is).

An expander increases the gain of that part of the signal that exceeds the threshold but thats because it works exactly like a compressor but has a compression ratio of less than 1:1 (i.e. 0.5:1)

A compressor doesn't bring out the 'click' in a kick drum - in fact, it supresses it. If you look at a straight 909 bass drum sample in a wave editor you will notice there is a very sharp, very sudden amplitude peak, then a sudden drop in amplitude as the wavelength increases. As the wave length increases, the frequency goes down so this is the bassiest part of the drum (the lowest part of the pitchbend).

Lets say the peak signal (the first and tallest peak) is at 0dB. If it isn't, normalise the drum so it peaks at 0dB. Now add a compressor.

Set the threshold to -3dB and imagine a horizontal line going across the screen at this point on the y axis. Everything above that line is going to get compressed. (this shouldn't be alot - its mainly the initial click bit.)

Compress it with a ratio of 3:1. This means that for every 3 dB over the threshold, the gain will be reduced to 1dB over the threshold. Everything that peaks below the line is unaffected.

Doing this with both the envelope attack and release will reduce the peak signal by 2dB. You can do this yourself in Soundforge or whatever, but make sure you can see it before and after compression and be able to measure how much the peak has gone down (Soundforge or Audition is ideal).

However, you now have 2dB extra dynamic range, so you can increase the output gain by 2 more dB. Not only that, but everything below our imaginary line is 2dB louder in relation to peak signal (its like a balancing scale. You have taken a weight off 1 scale thus making it lighter compared to the other scale).

Since this is the bassiest part of the drum, it gives the impression that the whole kick drum is bassier. That takes a little emphasis off the click at the start.

I suppose you could say that makes it seem 'warmer'.

If you were to compress this drum to an extreme degree (i.e. using a very low threshold and very high compression ratio) you can completely collapse that initial loud peak and turn it into a very bassy smudge.

Try compressing the same 909 BD with:

Threshold = -50dB
Ratio = 10:1
Output Gain = 0
Envelope Attack = 0
Envelope Release = 0
Knee = Hard

Dont worry about it blowing your head off - it will be very very quiet (to be exact, 45dB quieter). Now, normalise it to 0dB and turn down your speakers. There will be practically no click at all.

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Originally posted by Derivative A compressor doesn't bring up anything and is totally not sensitive to frequency - only the amplitude of a signal.

Compressor does change the amplitude of different frequencies by altering the dynamics of the signal. It can bring up or down frequencies.

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Since this is the bassiest part of the drum, it gives the impression that the whole kick drum is bassier.

It�s not an impresssion, the kick drum is bassier.

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Originally posted by Chronosis Compressor does change the amplitude of different frequencies by altering the dynamics of the signal. It can bring up or down frequencies.

Please explain step by step how a compressor raises the amplitude of any frequency provided you don't touch the output gain or use a threshold less than 1:1 (i.e. by not using an expander).

A compressor by its very definition reduces dynamic range. It does not increase it. Ever. Unless you use an expander.

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It�s not an impresssion, the kick drum is bassier.

In this example yes. But if you don't use a bassdrum you will get different results. Say the loudest part of the sound you are compressing is low frequency and the rest is high. Then the opposite will be true.

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Originally posted by Chronosis Compressor does change the amplitude of different frequencies by altering the dynamics of the signal. It can bring up or down frequencies.

Derivitive is right technicaly, it can't bring up anything, a compressor can only bring amplitude DOWN.

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Originally posted by Derivative Please explain step by step how a compressor raises the amplitude of any frequency provided you don't touch the output gain

Technically it doesn't, but it can make certain frequencies RELATIVELY louder, even though it's doing so via gain reduction. But you know this.

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In this example yes. But if you don't use a bassdrum you will get different results. Say the loudest part of the sound you are compressing is low frequency and the rest is high. Then the opposite will be true.

I said the same exact thing earlier in the thread. Basically I agree with everything you've said.

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Originally posted by Derivative Please explain step by step how a compressor raises the amplitude of any frequency provided you don't touch the output gain or use a threshold less than 1:1 (i.e. by not using an expander).

the thread title 'using a compressor to add warmth' would suggest that the compressor 'make up gain' would be used. without it you just get a quieter signal.

if a track is cold sounding (with prominant midhigh's) then the compressor will take these cold sounds down in level. hit the make up gain and the sound is perceived to be warmer. its simple.

He was just trying to make the point our terminology is wrong, a compressor doesn't raise the amplitude of any frequency he's 100% correct. I guess technically we shouldn't say "adds warmth" but "reduces cold"

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Originally posted by mysticalninja He was just trying to make the point our terminology is wrong, a compressor doesn't raise the amplitude of any frequency he's 100% correct. I guess technically we shouldn't say "adds warmth" but "reduces cold"

maybe a better way would be

'compression reduces prominant cold sounding frequencies(if they exist in the mixdown) so they no longer stand out in the mix. this, and then the use of make up gain to bring the full spectrum up in volume, means the end result has a more rounded and less cold sound'

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Originally posted by richg101 maybe a better way would be 'compression reduces prominant cold sounding frequencies(if they exist in the mixdown) so they no longer stand out in the mix. this, and then the use of make up gain to bring the full spectrum up in volume, means the end result has a more rounded and less cold sound'

What it the track in question is very bass-heavy, this would mean a compressor would do just the opposite .

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