Using the excellent RubberFilter by Christian Budde and Voxengo SPAN to analyse the frequency response of the various filter modes, we can see that:
- 12dB = Renoise Filter 24dB 4Pole ( Not a perfect match, but pretty damn close )
- 24dB = Renoise Filter Butterworth 4n
- 48dB = Renoise Filter Butterworth 8n
You'll see in the screenshots below that RubberFilter's 24dB mode is a perfect match for Renoise's Butterworth 4n mode, and that RubberFilter's 48dB mode is a perfect match for Renoise's Butterworth 8n mode. This comes as no big surprise since RubberFilter itself is also built on Butterworth filters.
Renoise 24dB 4Pole Highpass 1000Hz vs RubberFilter 12dB Highpass 1000Hz
Renoise Butterworth 4n Highpass 1000Hz vs RubberFilter 24dB Highpass 1000Hz
Renoise Butterworth 8n Highpass 1000Hz vs RubberFilter 24dB Highpass 1000Hz
Unfortunately, achieving a matching 6dB slope was not so simple. At first I thought Renoise's 24dB Moog might be a good match for a 6dB slope, but here we can see that this is not the case:
Renoise 24dB Moog Highpass 1000Hz vs RubberFilter 6dB Highpass 1000Hz
I suspect that Renoise's 24dB Moog might actually have a response that is closer to a 3dB slope, but unfortunately RubberFilter does not have a 3dB option that I can test against, and at the moment I do not have any other suitable filter plugins that I trust.
Either way, it is actually possible to get an almost perfectly matching 6dB slope from Renoise's filter, but it does require a little bit of experimentation to adjust the frequency until it produces the same result. In this case I had to increase Renoise's filter frequency from 1000Hz to 2500Hz:
Renoise 24dB Moog Highpass 2500Hz vs RubberFilter 6dB Highpass 1000Hz
Anyway... I hope this is helpful to some people. The moral of the story is: don't be afraid to experiment. Also trust your ears more than your eyes... if it sounds ok, then it's probably ok!
Edited by dblue, 19 February 2010 - 23:37.