Forums > MaxMSP

vb.chevy~ roll-off

November 21, 2012 | 12:30 pm

given that the filter actually goes from 2-pole (biquad) 12dB/8ve up to 20 poles, is that really 120dB/8ve???

I find that kind of hard to grasp, especially because it’s not *that* much prone to self-oscillation.
If you increase the passband ripple the roll-off seems to become even steeper.


November 23, 2012 | 4:11 pm

given that the filter actually goes from 2-pole (biquad) 12dB/8ve up to 20 poles, is that really 120dB/8ve???

yes, and it’s easy to verify this yourself.
why do you wonder? do you run into problems using it?

vb


November 26, 2012 | 2:22 pm

Oh my it’s vb in person!
How is it verifiable? I came to this conclusion purely mathematically (as you can use the object for controlling stacked biquads). The filtergraph~ object is not really accurate for display.

Is the filter design exactly the same as in the biquad? The ripple seems to increase the steepness drastically even at 0.1%.

I didn’t run into any problems that aren’t inherent to steep filters by nature.

Great object by the way, it’s currently the heart of my project, would have been very difficult to pull it off without your filter.

I was wondering purely because you don’t come across many filters/plugins that would go so far as to implement anything more than 48db/8ve


December 1, 2012 | 6:10 pm

How is it verifiable?

you could use a sinusoid and measure peakamp or rms before and after the filter at different frequencies.

Is the filter design exactly the same as in the biquad?

yes, cascaded biquads.

Great object by the way, it’s currently the heart of my project, would have been very difficult to pull it off without your filter.

thanks, always nice to hear that things you share turn out to be useful to others.

I was wondering purely because you don’t come across many filters/plugins that would go so far as to implement anything more than 48db/8ve

well, now there is even one in max6. take a look at [filterdesign], which renders my humble object superfluous, i guess.


December 2, 2012 | 10:31 pm

I’ve seen it but I still prefer vb.cheby~ though, seems easier to handle for my purposes, and I already have a humongous object count.

Ah, cool. Filtergraph didn’t seem very accurate.


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