Compressor Ratio 0-1?

stefan · 20 Apr 2006

1 ought to be equal to inf:1.

You think it is important to have a x:y readout of the ratio? If so, why? I've never quite seen the benifit of it when using other compressors, and I've used a bunch 🙂

skOre · 20 Apr 2006

I guess this kind of display should be offered though. Maybe one could be able to switch?

Anyways, stef, what would the math be to compute the ratio from the 0-1 scale? That way, aetmos could build his own hack...

stefan · 20 Apr 2006

I would have to take a look at how normal ratios (x:y) work and how I actually use my ratio internally in the module 🙂

aetmos · 20 Apr 2006

You think it is important to have a x:y readout of the ratio? If so, why?

Yes, I think it's important, because it's the standard for setting a ratio on a compressor. When I'm using a compressor, I generally have a pretty good idea of where I want to set it for a particular task, and then I'll adjust to taste.

Anyways, stef, what would the math be to compute the ratio from the 0-1 scale? That way, aetmos could build his own hack...

Yes, that would be fine.

I would have to take a look at how normal ratios (x:y) work

The compression ratio is the ratio of input change to output change above the threshold. So, assuming that a signal is above the threshold, if the compressor is set to 2:1, an input level change of 2 dB will result in an output level change of only 1 dB.

stefan · 20 Apr 2006

Ok, basically I just wondered if the ratio was in dB or linear amplitude. Thanks. Will try to have a look at this if no-one else does first 🙂

aetmos · 20 Apr 2006

stefan wrote: Ok, basically I just wondered if the ratio was in dB or linear amplitude. Thanks. Will try to have a look at this if no-one else does first 🙂

Oh, yeah, definitely dB. Thanks!

Tom

stefan · 20 Apr 2006

Without looking into it my top-of-the-head-guess would be that the 0-1 can be converted into x:1 ratio like this:

let a = 0..1 ratio knob value x = 1 / (1 - a)

so when a = 0, the ratio will be 1:1 when a = 0.5, the ratio will be 2:1 when a = 1, the ratio will be inf:1

but I might be wrong 🙂

aetmos · 20 Apr 2006

I made a simplified compressor with only 1 band, and ran it through a scope, comparing it to the "Dynamics" compressor that comes with Cubase SX3. Your calculation seems to be reasonably accurate. Here's what I did:

- Both compressors set to the shortest possible attack time - Release on Cubase compressor set to auto, release on SynthMaker compressor set to the minimum that would not cause distortion - Softclip and Ahead set to 0 on SynthMaker compressor (n/a for Cubase compressor). - The test signal was a 440Hz Sine Wave, played at -7dB

The numbers

[b]Cubase Compressor[/b]

Input Output w/ Peak Output w/ RMS Ratio Threshold ------- ----------------- ----------------- ------ ----------- -7dB -7.2dB -8.0dB 2:1 -9dB -7 -7.3 -8.5 4:1 -9 -7 -7.3 -8.7 8:1 -9 -7 -12.7 -13.5 2:1 -20 -7 -15.5 -16.7 4:1 -20 -7 -16.9 -18.4 8:1 -20

[b]SynthMaker Compressor (only 1 output choice)[/b]

(because of the GUI controls, I had some difficulty setting exactly the same values as used with the Cubase Compressor)

Input Output Ratio (x:x) Ratio (0-1) Threshold ------- ----------------- ------------- ------------ ----------- -7 -8 2:1 0.4995 -9.375 -7 -8.6 3.99:1 0.74925 -9.375 -7 -8.8 7.94:1 0.874125 -9.375 -7 -13.1 2:1 0.4995 -20 -7 -16.1 3.99:1 0.74925 -20 -7 -17.6 7.94:1 0.874125 -20

Thanks, Tom

infuzion · 21 Apr 2006

aetmos wrote: You think it is important to have a x:y readout of the ratio? If so, why?

Yes, I think it's important, because it's the standard for setting a ratio on a compressor. When I'm using a compressor, I generally have a pretty good idea of where I want to set it for a particular task, and then I'll adjust to taste.

Yea, I have a collection a magazine article to say use a certain ratio for what ever instrument.

Thanks for the chart Tom.