Kuba wrote:
> Hi,
> I would like to make a combo filter (HPF and LPF) and have a lienar phase.
> 
> I think I use a Butterworth IIR filter

   ...

Linear phase implies FIR. Cascading a high-pass with a low-pass gives 
you a band-pass filter. Is there a reason you don't do that directly?

Jerry
-- 
Engineering is the art of making what you want from things you can get.
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Hi,
I would like to make a combo filter (HPF and LPF) and have a lienar phase.

I think I use a Butterworth IIR filter

Kuba


Uzytkownik "Rune Allnor" <allnor@tele.ntnu.no> napisal w wiadomosci 
news:1121174181.222049.181950@g14g2000cwa.googlegroups.com...
>
>
> Kuba wrote:
>> Hallo,
>>
>> I'm a student and I'm makins an audio device. I have to make a allpass
>> filter or lowpass and highpass, one after another.
>> The point is that i have to cutt  the audio band at about 20Hz and at 
>> about
>> 20kHz to get good signal parametres before parametric equalizer.
>>
>> Do You have some sugestions what kind of filters would be best in this
>> case(IIR or FIR and what kind)?
>> It will be implemented on TI 6713 DSP but the filters will be designed in
>> Matlab.
>> Maybe someone have done dhat kind of filters in Simulink and could give 
>> me
>> some help
>
> Hmmm, I don't really understand what you try to do. The cascaded
> high-pass
> (HPF) and low-pass (LPF ) filters make sense, given the constraints on
> your signal. Are you sure you want to make an all-pass filter that
> *replaces* the LPF + HPF combo? Or do you want an all-pass filter that
> corrects the phase the signal after having been band-pass filtered?
>
> Rune
> 

"Kuba" <kubabanasik@o2.pl> wrote in message 
news:db084k$bn6$1@nemesis.news.tpi.pl...
> Hallo,
>
> I'm a student and I'm makins an audio device. I have to make a allpass filter 
> or lowpass and highpass, one after another.
> The point is that i have to cutt  the audio band at about 20Hz and at about 
> 20kHz to get good signal parametres before parametric equalizer.
>
> Do You have some sugestions what kind of filters would be best in this 
> case(IIR or FIR and what kind)?
> It will be implemented on TI 6713 DSP but the filters will be designed in 
> Matlab.
> Maybe someone have done dhat kind of filters in Simulink and could give me 
> some help

You probably want to use IIR, since filtering at 20Hz with a high sample rate 
(I'm assuming at least 44.1kHz) takes a very long filter.  Check out 
http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt for some information on 
calculating IIR filter coefficients. 

Kuba wrote:
> Hallo,
>
> I'm a student and I'm makins an audio device. I have to make a allpass
> filter or lowpass and highpass, one after another.
> The point is that i have to cutt  the audio band at about 20Hz and at about
> 20kHz to get good signal parametres before parametric equalizer.
>
> Do You have some sugestions what kind of filters would be best in this
> case(IIR or FIR and what kind)?
> It will be implemented on TI 6713 DSP but the filters will be designed in
> Matlab.
> Maybe someone have done dhat kind of filters in Simulink and could give me
> some help

Hmmm, I don't really understand what you try to do. The cascaded
high-pass
(HPF) and low-pass (LPF ) filters make sense, given the constraints on
your signal. Are you sure you want to make an all-pass filter that
*replaces* the LPF + HPF combo? Or do you want an all-pass filter that
corrects the phase the signal after having been band-pass filtered?

Rune

Hallo,

I'm a student and I'm makins an audio device. I have to make a allpass 
filter or lowpass and highpass, one after another.
The point is that i have to cutt  the audio band at about 20Hz and at about 
20kHz to get good signal parametres before parametric equalizer.

Do You have some sugestions what kind of filters would be best in this 
case(IIR or FIR and what kind)?
It will be implemented on TI 6713 DSP but the filters will be designed in 
Matlab.
Maybe someone have done dhat kind of filters in Simulink and could give me 
some help


Thanks,
Kuba