[PD] rzero or rpole first?

[Miller Puckette]

Wow, version control trouble again...  the figures are indeed configured
differently from the patches.  I looked around and say that the patch,
H11.shelving.pd, dates to August 2005 and I changed the figure between 
versions 08 and 09 of the book, sometime in mid 2006.  So I was revising my
thinking, but I left no trace of what the revision was, and didn't propagate
the change back to the text in that section, nor to the H11 patch.

In one way of thinking, it's correct for the output of a shelving or peaking
filter to change discontinuously when the coefficients change discontinuously,
because you're in fact asking for the frequency response to change and an
incoming sinusoid should get its amplitude changed immediately.  I think
on that reasoning the zcero~ should go afterward.  And then, one should
control the discontinuity by only changing the filter characteristics
continuously.

At one point I spent some time trying to get the butterworth filters
to work smoothly with changing coefficients.  I tried with zeros before
the poles and after, both as a batch and in pairs, and never got satisfactory
results.

I've stuck this in my small but growing errata file - thanks for flagging
it!

Miller


On Mon, Nov 17, 2008 at 03:43:20PM +0100, Frank Barknecht wrote:
> Hallo,
> 
> hm, I'm a bit confused how to place elementary filters: In the book,
> Miller writes that the r/czero should be placed before the poles and
> the screenshots also show this:
> http://crca.ucsd.edu/~msp/techniques/latest/book-html/node160.html
> 
> However the example patches (H11 ff.) and the butterworth abstractions
> that come with Pd have it the other way around and follow the
> alphabetic order with *z*ero last!
> 
> Ciao
> -- 
>  Frank Barknecht            Do You RjDj.me?          _ ______footils.org__
> 
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