> See
>
> P. Regalia and S. Mitra, "Tunable digital frequency response
> equalization filters," IEEE Trans. Acoust., Speech, Signal Processing,
> Vol. 35, No. 1, pp. 118-120, Jan 1987
>
> Juha
I haven't seen the paper yet, but the title implies altering the
frequency response. How might that be done with all-pass filters?
My remark about needing two breaks to create a shelf was true, but the
hunch (I knew better!) that first-order couldn't provide them was false.
http://www.harmony-central.com/Computer/Programming/Audio-EQ-Cookbook.txt
and http://www.theworld.com/~cmoore/AN11.pdf show nice counterexamples.
Jerry
--
Engineering is the art of making what you want from things you can get.
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