maybe im missing something but why not use pareq with steep resonance and negative gain?


On Thursday, December 5, 2013 at 9:21 AM, vallste@libero.it wrote:

> Dear List,
> I'd like to remove some frequencies zones (a band reject filter) from a signal with very precise frequency bands (high rolloff?). My Idea is somehow the following (Butterworth filters just for reference):
> 
> ainputSignal;Incoming signal
> ainputSignalB1 butlp ainputSignal, kfreq1 ;Band1
> ainputSignalB2 butbp ainputSignal, kfreq2, kband2 ;Band2
> ainputSignalB3 butbp ainputSignal, kfreq3, kband3 ;Band3
> ainputSignalB4 buthp ainputSignal, kfreq4 ;Band4
> 
> then the single bands are processed (or not) indipendently; If I modify only one band I can remove (from the input signal) only the band I want modify and sum the band once processed while keeping the rest of the signal intact. For example if I process only Band2:
> 
> aoutputSignal = ainputSignal - ainputSignalB2 + ainputSignalB2Pocessed
>  
> 
> 
> ainputSignalB1 butbp ainputSignal, kfreq1, kband1
> 
> 
>  
> Does this make sense or there are some phase modifications (in the filtered signals) to take in account?
> Then, which filters (or combination of, or pvs tricks, or...) to use (instead of the Butterworth written above) to have a very steep rolloff but being able to run the thing in realtime (on an average machine, not a supercomputer nor a pentim 2)?
> 
> Ciao
> 
> Stefano
>