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Equivalents

August 29, 2009 | 1:34 pm

Hello there!
Just a simple question… Does anybody knows which are the
objects as the Pure Data’s rpole~ and rzero~ in max/MSP??
Thank u very much! Smile


January 11, 2011 | 1:29 am

I’m having fun working through Andy Farnell’s "Designing Sound" book and have run into this as well. Farnell writes about using rzero~ for "differentiation" – the opposite of integrating a signal. I’ve gotten similar results using a hipass filter at 0.999 Hz. Is there a more exact equivalent for rzero~?

The pd help file says this about rzero~:
"rzero~ real one-zero (non-recursive) filter, raw

Rzero~ filters an audio signal (left inlet) via a one-zero real filter, whose coefficient is controlled by a creation argument or by an audio signal (right inlet).

The action of rzero~ is: y[n] = x[n] – a[n] * x[n-1]
where y[n] is the output, x[n] the input, and a[n] the filter coefficient. The filter is always stable.
The transfer function is H(Z) = 1 – aZ^-1."


January 27, 2011 | 5:00 pm

Here’s an rzero~ abstraction based on the filter equation given in the PD help patch. Seems to work fine. rpole~ can’t be built as an abstraction since it’s a recursive filter. I tried wrapping it in a poly~ set to vs 1, but it didn’t work properly.

– Pasted Max Patch, click to expand. –

January 27, 2011 | 10:14 pm

rpole~ can be build as an abstraction, as its a special case of a biquad~ ( which is rzero~as well btw):

– Pasted Max Patch, click to expand. –

February 6, 2011 | 9:00 pm

Very helpful! biquad~ is the way to go. It’s been a good exercise for me to build these filters from the ground up (with delay~, +~, etc.). Now it makes perfect sense to me how zeroing a1, a2 and b2 causes biquad~ to function as a single pole filter. Thanks!


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