[PD] pd filter with pole and zero

[cyrille henry]

hello,

i know there is a lot's of filter externals available for pd, but i'd like to use some using rpole~ / cpole~ etc.
my main motiviations are : 
1) i don't like using externals
2) this object allow an audio control of the cutoff frequency

as there is not a lot's of exemples, i'd like to know if anyone used this objects to make good filter abstraction.
or anyone have references in order to disign filter?
(i'm looking for a low pass resonant filter by exemple)


thanks
Cyrille