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Understanding ratio with compression.
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Chemogen
IsraTrance Full Member
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Posted : Jan 28, 2008 18:41
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Compression is one technique that while I understand the concept of, I don't really know how to use efficiently. One thing that I'm not 100% clear on is Ratio.
When the signal goes above the threshold, the gain of the signal is reduced by an amount controlled by the ratio control. For example, with the ratio set at 2:1, an increase in input of 2 dB above the threshold will result in an increase in the output of only 1 dB. Higher ratios yield more compression, but only to signals that pass above the threshold.
So does this mean that if I have a threshold of -10db and a ratio of 4:1, every time my sound hits -6db, it will be taken down to -9db? Then if I want to get that to -7db, I'd put the make-up gain up 2db?
I know it depends entirely on the sound, but how high are your thresholds? I'm using compression on my bass with a threshold of -13db, ratio of 3:1 and make-up of 3.5db which sounds quite tight.
When you would take your threshold down to something like -30db? |
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Alex Roudos
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Posted : Jan 28, 2008 19:08
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From my experience, the most important is how many dbs of gain reduction are required in order not to squash the sound by overcompressing it.
There are general rules for different sounds(kick, bass, voice etc.) about the recommended ratio, attack and release times. But the threshold level is totally dependent on the original dynamic level of the sound. Softer sounds(thin waveforms) require lower threshold and vice versa or alternatively/in combination, the input level of the compressor can be used.
I never compress more than 4-6dbs while mixing depending on the sound and i never use the makeup gain in the way it's supposed to be. I set everything in a way that the compressor is always working but never going more of 6dbs of gain reduction, then i add some make up gain to bring the volume of the sound on the same level as it was before compressing, in a way that when i turn on/off the comp there's no change in the volume level.
I do this because i prefer to add the missing dbs by an eq following the comp.
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Elad
Tsabeat/Sattel Battle
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Posted : Jan 28, 2008 19:45
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chemogen you got it right its ecacly like that
with that try as much diffrent types as you can to find the ones you like the most - diffrent compressors have diffrent outcome
and the is "hard knee" factor like in Rcomp where it will reduce the sound little bit also before it get to the treshold , in order to make it more "natural" (then i use it with lower tresh usualy)
another factor is the attack / realese options
attack will be the compression "fade in" and realese is how long it will keep compress after the sound is below the tresh , adjust according to taste
another thing before adding compressor - sometime worth to bounce wav file and look if it realy peaky and need the compressor or simple gain change will give the desired level
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Colin OOOD
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Posted : Jan 28, 2008 19:47
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... aaaaaand to answer the question:
"If I have a threshold of -10db and a ratio of 4:1, every time my sound hits -6db, it will be taken down to -9db? Then if I want to get that to -7db, I'd put the make-up gain up 2db?"
Yes, dependant on the attack time, of course, which is the time the compressor takes to reduce the gain when the level rises above the threshold.
"I know it depends entirely on the sound, but how high are your thresholds? I'm using compression on my bass with a threshold of -13db, ratio of 3:1 and make-up of 3.5db which sounds quite tight."
The threshold I use depends totally on the level of the sound going into the compressor. Yes, it depends totally on the sound.
"When you would take your threshold down to something like -30db?"
This is sometimes done in mastering to ensure that the whole dynamic range is compressed, not just the loudest parts, and can often really help to 'glue' a track together. Low thresholds like this are generally used with ratios of less than 2:1 to avoid overcompression. There are also creative applications of low thresholds; with a short release and an attack longer than about 10ms you can use them to bring out the attack of percussive sounds, or use them to iron out pads, for example.
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Alex Roudos wrote:
i never use the makeup gain in the way it's supposed to be. I set everything in a way that the compressor is always working but never going more of 6dbs of gain reduction, then i add some make up gain to bring the volume of the sound on the same level as it was before compressing, in a way that when i turn on/off the comp there's no change in the volume level. |
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As far as I know that's the recommended way to use the makeup gain, and in fact is where it gets its name from - it's used to make up the level lost during compression.
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Alex Roudos
IsraTrance Junior Member
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Posted : Jan 28, 2008 20:31
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Colin, you are right, but i said that as i have noticed that all plugin comps that offer an auto make up gain option, they add too much gain, and frankly i don't understand why.
A friend told me once that the biggest mistake we make is that we believe we live, when in reality we are sleeping in the waiting room of life. |
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Trip-
IsraTrance Team
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Posted : Jan 29, 2008 08:29
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Iron out pads? Just wondering about the meaning of it.
As you mentioned about low thresholds, a higher attack setting really reminds an exciter, which has raios below 1.
Crackling universes dive into their own neverending crackle...
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Tomos
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Posted : Jan 29, 2008 12:10
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Do all of the thresholds mentioned in this thread only apply to normalised recordings (or sounds recorded near 0db)
Because when I use a compressor with a simple visual feedback, the compressor appears to become active only when the threshold is around -30db if the sound was recorded very quietly. |
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Trip-
IsraTrance Team
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Posted : Jan 29, 2008 12:18
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Yes Tomos, usually speaking of high level signals - as in most situations.
Crackling universes dive into their own neverending crackle...
AgalactiA |
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PoM
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Posted : Jan 29, 2008 14:53
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Quote:
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On 2008-01-28 20:31, Alex Roudos wrote:
Colin, you are right, but i said that as i have noticed that all plugin comps that offer an auto make up gain option, they add too much gain, and frankly i don't understand why.
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me too i don t like that , i never use the make up gain, i think their target is to set the output neer 0 db .
about the ratio ,open a kick in a sound editor ,get 4 db of reduction (on the compresssor reduction metter) with a ratio of 2.1 then use a 6.1 ratio and hear what it does, you can render them to see the waveforms.
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PoM
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Posted : Jan 29, 2008 15:08
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Quote:
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On 2008-01-29 12:10, Tomos wrote:
Do all of the thresholds mentioned in this thread only apply to normalised recordings (or sounds recorded near 0db)
Because when I use a compressor with a simple visual feedback, the compressor appears to become active only when the threshold is around -30db if the sound was recorded very quietly.
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treshold value are useless in fact,it s the reduction that matter. (for example if you read on a bass get the treshold at - 12 ... it s totaly usless cause it depends at what level the source is )
you mixed treshold with ratio maybe . |
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Tomos
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Posted : Jan 29, 2008 15:44
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That's what I thought.. just checking. The only useful bit of information therefore must be peak db, so you can effectively set the threshold. |
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-aeon-
Aeon
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Posted : Jan 29, 2008 15:52
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Quote:
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follow your ears.
remember that any signal processing that can be used can be abused, often to great effect - compressing the fuck out of a drum loop can give it an entirely new feel and flavour, for example.
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PoM
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Posted : Jan 29, 2008 15:55
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Quote:
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On 2008-01-29 15:08, PoM wrote:
treshold value are useless in fact,it s the reduction that matter. (for example if you read on a bass get the treshold at - 12 ... it s totaly usless cause it depends at what level the source is )
you mixed treshold with ratio maybe .
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maybe with a sound at - 10 db and one at - 30 db using the same amount of compression and same setting you ll not have the same sound in the end, cause different treshold value may have different knee curve but i m not sure about that. |
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Trip-
IsraTrance Team
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Posted : Jan 30, 2008 14:42
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PoM,
a sound source at -10dB level and the same sound source at -30dB level, will get a different treatment from a 'same threshold setting' compressor.
Crackling universes dive into their own neverending crackle...
AgalactiA |
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UnderTow
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Posted : Jan 31, 2008 14:56
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Quote:
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On 2008-01-29 15:44, Tomos wrote:
That's what I thought.. just checking. The only useful bit of information therefore must be peak db, so you can effectively set the threshold.
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Or the RMS level depending on the detection algorithm in the compressor.
UnderTow |
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