How to choose Ratio on a compressor?

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There are videos all over the web about how to use a compressor, mostly to set Attack and Release, but isn't it weird that no one talks about how to choose a ratio besides saying that "2:1 is light compression", "10:1 is almost limiting" and "the common ratio is 4:1"?

How do you people choose a ratio value and why?

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the ratio determines what happens once the signal goes past the threshold. at 4:1, for every dB after threshold, the audio gets lowered by 4dB. say you're 5dB above threshold, that's 20dB of reduction on the audio. that's an easily audible change, whereas 2:1 gives you 10dB gain reduction, and has a lighter effect on the sound at the same threshold.
so, you use the threshold to determine how often compression happens, not how strong it is, that's the ratio's role.

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acYm wrote: Fri Feb 01, 2019 5:22 am the ratio determines what happens once the signal goes past the threshold. at 4:1, for every dB after threshold, the audio gets lowered by 4dB. say you're 5dB above threshold, that's 20dB of reduction on the audio. that's an easily audible change, whereas 2:1 gives you 10dB gain reduction, and has a lighter effect on the sound at the same threshold.
so, you use the threshold to determine how often compression happens, not how strong it is, that's the ratio's role.
That's the technical stuff, but how do you translate that into more "musical" language? How do you feel the different rations sound?

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well, a higher ratio means more reduction of the dynamic range, therefore.
on a limiter, the audio signal is not allowed to go past the threshold (or ceiling), right? on a compressor, it can, and how much does is determined by the ratio.

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My tip: not high, unless you do some serious sound design (ie. creating clap from noise) or try to fix very unbalanced sounds in first place.

I usually do multiband compression with 4:1 for low-end, 2:1 for bass, 1.7 - 1.5 for mids and 1.3 for highs as a starting point.
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a quick google search lists quite a few videos on compression ratio

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acYm wrote: Fri Feb 01, 2019 5:22 am the ratio determines what happens once the signal goes past the threshold. at 4:1, for every dB after threshold, the audio gets lowered by 4dB. say you're 5dB above threshold, that's 20dB of reduction on the audio. that's an easily audible change, whereas 2:1 gives you 10dB gain reduction, and has a lighter effect on the sound at the same threshold.
so, you use the threshold to determine how often compression happens, not how strong it is, that's the ratio's role.
REALLY... dammn I never knew that!
Is this is what your compressor's gain reduction meter shows...
I must re_calibrate my meters I guess.

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toonertik wrote: Fri Feb 01, 2019 3:29 pm
acYm wrote: Fri Feb 01, 2019 5:22 am the ratio determines what happens once the signal goes past the threshold. at 4:1, for every dB after threshold, the audio gets lowered by 4dB. say you're 5dB above threshold, that's 20dB of reduction on the audio. that's an easily audible change, whereas 2:1 gives you 10dB gain reduction, and has a lighter effect on the sound at the same threshold.
so, you use the threshold to determine how often compression happens, not how strong it is, that's the ratio's role.
REALLY... dammn I never knew that!
Is this is what your compressor's gain reduction meter shows...
I must re_calibrate my meters I guess.
There's a reason you never knew that. This information is slightly garbled.

A ratio of 4:1 simply means that you put 4 in and get 1 out. So for every +4dB over the threshold, the signal is attenuated by -3dB, resulting in a signal +1dB over the threshold.

So +20dB over the threshold with a ratio of 4:1 is going to give you +5dB over the threshold, which is a reduction of -15dB.

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Exactly .. I had my tongue in my cheek :wink:

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toonertik wrote: Fri Feb 01, 2019 4:04 pm Exactly .. I had my tongue in my cheek :wink:
Ah. It didn't translate for some reason. I could have left it but thought it best to clear things up for those just learning.

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Not that i'm expert but when adjust threshold and ratio just listen how pumped or transparent sound you get,between -6-12db and ratio 1,5-3 should work in most cases :)

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VELLTONE MUSIC wrote: Fri Feb 01, 2019 7:46 pm Not that i'm expert but when adjust threshold and ratio just listen how pumped or transparent sound you get,between -6-12db and ratio 1,5-3 should work in most cases :)
So 3:1 and smaller and ratios are more-or-less transparent? Do you mean regarding distortion or the dynamics?

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wow, good thing I'm not a math major, looks like my equation was ass-backwards then. that does make more sense.
I guess "intensity" could be a more musical label for the parameter...
lower ratio is more subtle, higher has more force

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heavymetalmixer wrote: Fri Feb 01, 2019 8:19 pm
VELLTONE MUSIC wrote: Fri Feb 01, 2019 7:46 pm Not that i'm expert but when adjust threshold and ratio just listen how pumped or transparent sound you get,between -6-12db and ratio 1,5-3 should work in most cases :)
So 3:1 and smaller and ratios are more-or-less transparent? Do you mean regarding distortion or the dynamics?
on the topic question:use less ratio around 1,5-3 if you want u mix to be more natural and transparent,use 4-8 to achieve more compressed tight sound,10 or 20 is extreme...anyway this is basic,i'm not mixing engineer,just can hear the difference,for example put threshold on -12 then turn ratio between 1,5 and 3 and u will see the difference,when apply it on individual tracks is different you may look for specific sonic distortion,i am talking about final mix dynamic,some basic help...i still learn it:)Cheerz :)

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It doesn't seem to have been mentioned but one should use the ratio and threshold controls in tandem, ie the more of the one the less of the other (unless you're going special fx, of course :D ). So if you have a very low threshold (ie compression kicks in sooner) you would have a low ration ratio (2:1, for example). Conversely, if you had a high ratio (eg 8:1) you'd have a high threshold (compression would kick in later).
You shouldn't twiddle the one in isolation.

Thank you for your attention. :D :tu: :party:
TGIF!

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