Re: [sc-users] 30hz high pass mastering

Hi guys,

chiming in on this discussion; in wslib I made a set of cascaded filters with Butterworth coefficients. This doesn't ensure a "perfect" filter, but it behaves better than simply stacking HPF's (which would actually be a Linkwitz Riley filter, with a -3dB drop at the cutoff frequency). As I understand this design minimizes rippling and ringing. I don't know about group delay/phase distortion on these, but I think they are about as good as it gets for this purpose. The class is called BLowCut, based on the BEQ suite filters. Example:

{ BLowCut.ar( PinkNoise.ar(0.1), 30, 2 ) }.play; // 4th order Butterworth (0 = no order, 1 = 2nd order, 2 = 4th order .. 5 = 10th order)

Btw, if anyone on the list has experience with designing linear-phase filters in SC I would be very interested :-)

cheers, Wouter

Op 19 dec. 2017, om 15:35 heeft jamshark70@xxxxxx het volgende geschreven:

daniel-mayer wrote
Perhaps in terms of amplitude, but I bet a Butterworth highpass will be
more
spectrally transparent.

HPF *is* a Butterworth highpass.

Well, yes, which is why I mentioned it. I wasn't saying "a Butterworth
filter would be better than HPF"; I meant to say "HPF, as a Butterworth
filter, is spectrally transparent in a way that FFT is not guaranteed to
be."

I checked your example with cascaded BHiPass4 and got better results than
with HPF, but not close to PV_Brickwall.

Again, "better" in what way?

A mastering filter had better minimize rippling in the frequency response.
If you're only measuring the severity of the attenuation, you're
demonstrating strong attenuation but that may not make it a better filter to
the ear.

hjh

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