J-Texas wrote on Fri, 16 May 2008 13:02 |
beau wrote on Fri, 16 May 2008 10:05 |
J-Texas wrote on Fri, 16 May 2008 06:12 |
Adam Miller wrote on Fri, 16 May 2008 03:09 |
Fig wrote on Thu, 15 May 2008 21:33 |
J, 4:1 seems like a LOT to me on the 2-bus. If you're seeing 1-3 dB of reduction, that's 4 - 12 dB of dynamic range you are sucking up.
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Eh? How does that work?
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4 to 1
4 times 3dB of reduction = 12db of dynamics you're sucking up!
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not really the case from what i understand.
A compressor reduces the gain (level) of an audio signal if its amplitude exceeds a threshold. The amount of gain reduction is determined by a ratio. For example, with a ratio of 4:1, when the (time averaged) input level is 4 dB over the threshold, the output signal level will be 1 dB over the threshold. The gain (level) has been reduced by 3 dB. When the input level is 8 dB above the threshold, the output level will be 2 dB; a 6 dB gain reduction. A more specific example for a 4:1 ratio: using a digital dbfs meter.
Threshold = ?10 dB Input = ?6 dB (4 dB above the threshold) Output = ?9 dB (1 dB above the threshold)
paece
beau
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I know you can't figure this out with an equation like I wrote! That was the only thing that would equal twelve.
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Sure you can calculate the gain reduction with an equation.
The ratio defines HOW MUCH the signal gets compressed (once it is over the threshold).
The gain reduction just tells how much gain is reduced, nothing more, no more calculation nothing. 3dB gain reduction = 3dB less dynamics, simple as that (note this doesn't take into acount the attack and release so the overall dynamic reduction might be much lower due to the attack still letting spikes thru etc., but the instantious dynamic reduction at the time the meter reads a value is exactly that value and nothing else (this is highly dependent on the accuracy and lag time of the meter though)).
So to comeback to that formula thing:
in: is your input signal, in dB
out: output, in dB
thresh: threshold, in dB
ratio: ratio, given as a ratio like x:1 = x
gr: gain reduction, in dB
so let's see, let's say in will go above the thresh, then you'll get: (THIS IS JUST THE OUT(t) = F(IN(t)) FUNCTION, attack and release come in to play on how fast the compressor will reach the desired output level)
thresh + (in-thresh)/ratio = out
with this gr can be calculated as follows:
gr = in - out
so an example in = -6dBFS, thresh = -10dBFS, ratio = 4:1 = 4
(calc with units omitted)
(-10) + ( (-6) - (-10) ) / 4 = (-10) + (4)/4 = -9
gr = -6 - (-9) = 3 dBFS
This is how ratio on a compressor works anyway ... for any further information refer to:
http://en.wikipedia.org/wiki/Audio_level_compressionHopefully you'll understand the concept of a compressor after reading this and can finally get license to use a compressor back.
Sorry for this long technical post but I just couldn't not post
.