> Jerry Avins <jya@ieee.org> wrote in message news:<bor2ci$34q$1@bob.news.rcn.net>...
>
>>Zeros in the right-half s plane reduce a filter's "promptness" -- the
>>weighting of its impulse early on. Moving a zero to its conjugate
>>location -- reflecting it about the jw axis -- leaves the response for
>>real frequencies unchanged. For a filter of N zeros, there are exactly
>>[(2^n) - 1] other filters with exactly the same frequency response but
>>different impulse responses. If N is not too large, you can try them all.
>
>
> Thanks for the idea. Could you direct me to some good factorization
> algorithms? I've never worked with direct factorization, so I have no
> idea how the existing algorithms behave for the filters that are long
> enough. How about several hundred taps?
>
> Alex
"In theory, there's no difference between theory and practice. In
practice, there is." In a word: no. If an approximate solution will do,
you might look at IIR "equivalents". There, the factoring is done.
Jerry
--
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������
Reply by Jerry Avins●November 12, 20032003-11-12
Alexey Lukin wrote:
...
> Sorry if I made it unclear, but both Andor and me are talking about
> pre-ringing of FIR filters in the sound equalizers. As Andor pointed
> out, there are evidences that amount of (pre-)ringing affects the
> sound coloration. What I'm trying to do is just making some
> experiments with different phase responses of the filters. So I'm
> asking about the ways to design filters with different phase
> responses.
>
> Alex
Thanks.
Jerry
--
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������
Reply by Alexey Lukin●November 12, 20032003-11-12
Jerry Avins <jya@ieee.org> wrote in message news:<bor2ci$34q$1@bob.news.rcn.net>...
> Zeros in the right-half s plane reduce a filter's "promptness" -- the
> weighting of its impulse early on. Moving a zero to its conjugate
> location -- reflecting it about the jw axis -- leaves the response for
> real frequencies unchanged. For a filter of N zeros, there are exactly
> [(2^n) - 1] other filters with exactly the same frequency response but
> different impulse responses. If N is not too large, you can try them all.
Thanks for the idea. Could you direct me to some good factorization
algorithms? I've never worked with direct factorization, so I have no
idea how the existing algorithms behave for the filters that are long
enough. How about several hundred taps?
Alex
Reply by Alexey Lukin●November 12, 20032003-11-12
Jerry Avins <jya@ieee.org> wrote in message news:<bormb0$gtt$1@bob.news.rcn.net>...
> > Yes, my goal is the same: trying to reduce the pre-ringing.
> > The windowing of the pre-ringing is not a solution, because it heavily
> > distorts the frequency response of the filter. Isn't it the case in
> > your experiments?
> >
> > Alex
>
> You're keeping too much in your head. Pre ringing of what? If sound,
> what means do you use yo associate a particular amount of pre-ringing
> with a given coloration or lack of that? To "what are you trying to
> do?", you're answering "Climb onto the bus" instead of "Get to Miami."
Sorry if I made it unclear, but both Andor and me are talking about
pre-ringing of FIR filters in the sound equalizers. As Andor pointed
out, there are evidences that amount of (pre-)ringing affects the
sound coloration. What I'm trying to do is just making some
experiments with different phase responses of the filters. So I'm
asking about the ways to design filters with different phase
responses.
Alex
Reply by Jerry Avins●November 11, 20032003-11-11
Alexey Lukin wrote:
> an2or@mailcircuit.com (Andor) wrote in message news:<ce45f9ed.0311110717.7308ed8b@posting.google.com>...
>
>>I was suggesting an approach which tries to reduce pre-ringing for
>>linear-phase filters. What are you aiming at? You didn't specify how
>>and why you wanted the phase response to lie "between" linear and
>>minimum.
>>
>>Perhaps if you state your goal there are better ways.
>
>
> Yes, my goal is the same: trying to reduce the pre-ringing.
> The windowing of the pre-ringing is not a solution, because it heavily
> distorts the frequency response of the filter. Isn't it the case in
> your experiments?
>
> Alex
You're keeping too much in your head. Pre ringing of what? If sound,
what means do you use yo associate a particular amount of pre-ringing
with a given coloration or lack of that? To "what are you trying to
do?", you're answering "Climb onto the bus" instead of "Get to Miami."
Jerry
--
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������
Reply by Jerry Avins●November 11, 20032003-11-11
Alexey Lukin wrote:
...
> Just take the magnitude response of lin-phase filter, substitute some
> phase response, and take the inverse FFT. If you subst. the phase
> resp. of the min-phase filter - you get the min. phase filter. If you
> subst. the phase resp. of the lin-phase filter - you get the lin.
> phase filter. But if you subst. some intermediate phase response (an
> average, for example), you won't get any good filter, due to time
> domain aliasing (?) the magnitude response will be altered too.
> So the phase response must be carefully designed somehow, and not just
> thought out.
Zeros in the right-half s plane reduce a filter's "promptness" -- the
concentration of its impulse response early on. Moving a zero to its
conjugate location -- reflecting it about the jw axis -- leaves the
response for real frequencies unchanged. For a filter of N zeros, there
are exactly [(2^n) - 1] other filters with the same frequency response
but different impulse responses. For small N, you can try them all.
Jerry
--
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������
Reply by Alexey Lukin●November 11, 20032003-11-11
an2or@mailcircuit.com (Andor) wrote in message news:<ce45f9ed.0311110717.7308ed8b@posting.google.com>...
> I was suggesting an approach which tries to reduce pre-ringing for
> linear-phase filters. What are you aiming at? You didn't specify how
> and why you wanted the phase response to lie "between" linear and
> minimum.
>
> Perhaps if you state your goal there are better ways.
Yes, my goal is the same: trying to reduce the pre-ringing.
The windowing of the pre-ringing is not a solution, because it heavily
distorts the frequency response of the filter. Isn't it the case in
your experiments?
Alex
Reply by Jerry Avins●November 11, 20032003-11-11
Alexey Lukin wrote:
...
> Just take the magnitude response of lin-phase filter, substitute some
> phase response, and take the inverse FFT. If you subst. the phase
> resp. of the min-phase filter - you get the min. phase filter. If you
> subst. the phase resp. of the lin-phase filter - you get the lin.
> phase filter. But if you subst. some intermediate phase response (an
> average, for example), you won't get any good filter, due to time
> domain aliasing (?) the magnitude response will be altered too.
> So the phase response must be carefully designed somehow, and not just
> thought out.
Zeros in the right-half s plane reduce a filter's "promptness" -- the
weighting of its impulse early on. Moving a zero to its conjugate
location -- reflecting it about the jw axis -- leaves the response for
real frequencies unchanged. For a filter of N zeros, there are exactly
[(2^n) - 1] other filters with exactly the same frequency response but
different impulse responses. If N is not too large, you can try them all.
Jerry
--
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������
Reply by Andor●November 11, 20032003-11-11
Alexey Lukin wrote:
> > In the mean-time I had a couple of ideas on how
> > to go about implementing some kind of control over the pre-impulse ringing,
> > starting off with a linear-phase filter (resulting in a non-linear and
> > non-minimum-phase filter). One was to apply a "window" to the pre-impulse
> > response part (you can do this very easily by modifying FIR coefficients).
>
> Sure. But I believe this is not a proper way, unfortunately. For
> example, you can not get minimal phase filter from linear phase filter
> in this way. Any windowing alters the freqeuncy response
> significaltly. I'm looking for a way to get the desired phase response
> not altering the freeuncy response (similarly to how it can be done
> during lin-phase -> min-phase conversion).
I was suggesting an approach which tries to reduce pre-ringing for
linear-phase filters. What are you aiming at? You didn't specify how
and why you wanted the phase response to lie "between" linear and
minimum.
Perhaps if you state your goal there are better ways.
Regards,
Andor
Reply by Alexey Lukin●November 11, 20032003-11-11
"Andor" <an2or@nospam.com> wrote in message news:<3fae8c55_1@news.tiscalinet.ch>...
> I recently read a paper from Michael Gerzon (I don't have the link handy,
> and Google didn't turn it up, but I downloaded it from somewhere on the net)
> where he claimed that an ideal audio filter would have an impulse response
> somewhere "between" minimum and linear phase (not really specifiying by
> which metric to measure betweeness). Perhaps you have also read it.
I've read a similar paper by J. Smith.
> support is the "well known" fact, that audio EQ filters with a Q higher than
> a certain number (I think it was around 1.5) sounded "coloured" - the high Q
> results in a slower decreasing impulse response (longer ringing), which
> supposedly explains the "colouredness" (why not the amplitude response?).
I think that by "coloration" one could mean quite anything: from
pre-echos to time smearing of transients.
> I'm not so sure about these claims and would like to see them verified by
> independent listening tests. In the mean-time I had a couple of ideas on how
> to go about implementing some kind of control over the pre-impulse ringing,
> starting off with a linear-phase filter (resulting in a non-linear and
> non-minimum-phase filter). One was to apply a "window" to the pre-impulse
> response part (you can do this very easily by modifying FIR coefficients).
Sure. But I believe this is not a proper way, unfortunately. For
example, you can not get minimal phase filter from linear phase filter
in this way. Any windowing alters the freqeuncy response
significaltly. I'm looking for a way to get the desired phase response
not altering the freeuncy response (similarly to how it can be done
during lin-phase -> min-phase conversion).
> > Clearly, just mixing the phase responses of min.phase and lin.phase
> > filters is not a solution.
>
> What do you mean by "mixing phase responses"?
Just take the magnitude response of lin-phase filter, substitute some
phase response, and take the inverse FFT. If you subst. the phase
resp. of the min-phase filter - you get the min. phase filter. If you
subst. the phase resp. of the lin-phase filter - you get the lin.
phase filter. But if you subst. some intermediate phase response (an
average, for example), you won't get any good filter, due to time
domain aliasing (?) the magnitude response will be altered too.
So the phase response must be carefully designed somehow, and not just
thought out.
Best,
Alex