Hi, I am currently building a multiband compressor although I am struggling to implement a soft knee. Does anyone have any advice? Links to any useful writings on the subject would be much appreciated, struggling to find much...

Cheers

Maelstorm, I have tried downloading your compressor.mmd.pd patch although it will not open? should it work with pd 0.42.5-extended?

I have found this useful, although I have edited his formula slightly:

O = I - (( 1/R-1 )( I - T + K/2 )^2) / 4K

Instead of:

O = I + (( 1/R-1 )( I - T + K/2 )^2) / 2K

where;

O = Output (dB)
I = Input (dB)
T = Threshold (dB)
R = Ratio
K = Knee Width (dB)

I think i am yielding the correct results. For instance when
Threshold = 20dB, Ratio = 2 and Knee Width = 2dB

f(Input) = Output
f(19.1) = 19.09dB
f(20) = 19.87dB
f(20.9) = 20.44dB

These results seem fairly accurate; between the knee width we see a change in gain reduction, from very little at 19.1 to around 1:2 gain reduction at 20.9

Although I have a few issues, with an input gain of 20.9, gain reduction should <0.45, because the ratio is set at 1:2 and for a hard knee gain reduction would equal 0.45 but should be <0.45 for a soft knee. My gain reduction is 0.451?

If anybody could help me to get this soft knee working more accurately, it would be highly appreciated. I've attached a small patch with the soft knee calculation if you'd like to take a look...

Thank you

http://www.pdpatchrepo.info/hurleur/SoftKneeGainCalculation.pd

Thank you very much, this should be quite useful.

I've also found this very helpful if anyone is interested...

http://c4dm.eecs.qmul.ac.uk/audioengineering/compressors/documents/Giannoulis.pdf