> On 22 Wrz, 00:48, Piotrek Żelechowski <pezel...@gmail.com> wrote:
>>> A linear system can't treat one cycle differently from another.
>> I meant that for example 370' of delay is similar to 10' lead. And I
>> would like to use this effect. But I have to find tool which allow mi
>> to design filter with arbitrary amplitude and phase
>
> Sorry for accidentally duplicated
> And there is some mistake not 370' but 350'
A real lead involves predicting the future. I don't know how to do that.
Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
Reply by ●September 21, 20092009-09-21
On 22 Wrz, 00:48, Piotrek �elechowski <pezel...@gmail.com> wrote:
> > A linear system can't treat one cycle differently from another.
>
> I meant that for example 370' of delay is similar to 10' lead. And I
> would like to use this effect. But I have to find tool which allow mi
> to design filter with arbitrary amplitude and phase
Sorry for accidentally duplicated
And there is some mistake not 370' but 350'
Reply by ●September 21, 20092009-09-21
On 22 Wrz, 00:48, Piotrek �elechowski <pezel...@gmail.com> wrote:
> > A linear system can't treat one cycle differently from another.
>
> I meant that for example 370' of delay is similar to 10' lead. And I
> would like to use this effect. But I have to find tool which allow mi
> to design filter with arbitrary amplitude and phase
Sorry for accidentally duplicated
And there is some mistake not 370' but 350'
Reply by Piotrek Żelechowski●September 21, 20092009-09-21
> A linear system can't treat one cycle differently from another.
>
I meant that for example 370� of delay is similar to 10� lead. And I
would like to use this effect. But I have to find tool which allow mi
to design filter with arbitrary amplitude and phase
Reply by Piotrek Żelechowski●September 21, 20092009-09-21
> A linear system can't treat one cycle differently from another.
I meant that for example 370� of delay is similar to 10� lead. And I
would like to use this effect. But I have to find tool which allow me
to design filter with arbitrary amplitude and phase
Reply by Jerry Avins●September 20, 20092009-09-20
Piotrek Żelechowski wrote:
You are replying to Vladimir's post and to my words.
>> There is no way to
>> decrease a lag with a filter. Filters can only /add/ delay.
>
> Maybe is it possible to increase lag but in way which gives result
> similar to decrease but on the next period of signal ?? Something like
> that (http://obrazki.elektroda.net/39_1251985087.jpg)
A linear system can't treat one cycle differently from another.
>> Can your problem be solved by adding controlled amounts of delay? if
>> not, i don't see a solution.
> I’ve tried that. It would help only if I could add different amount of
> delay to each frequency in pass band (but It would be difficult and
> costs a lot of calculating power of processor)
Different delays at different frequencies is called dispersion. Avoiding
it costs calculating power. Getting it the way you like may cost too.
>> The first step is to come up with a precise statement of
>> the problem to be solved and the characteristics of an
>> acceptable - not ideal - solution.
Remember: adding delay to a feedback system rarely makes it more stable.
> I will try to make more measuring and write it more precise, however I
> think that the idea of problem is clear (?)
Think in terms of possibly variable time delay, rather than phase shift.
Negative delay can not usually be achieved.
Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
Reply by ●September 20, 20092009-09-20
>There is no way to
>decrease a lag with a filter. Filters can only /add/ delay.
Maybe is it possible to increase lag but in way which gives result
similar to decrease but on the next period of signal ?? Something like
that (http://obrazki.elektroda.net/39_1251985087.jpg)
>Can your problem be solved by adding controlled amounts of delay? if
>not, i don't see a solution.
I�ve tried that. It would help only if I could add different amount of
delay to each frequency in pass band (but It would be difficult and
costs a lot of calculating power of processor)
>The first step is to come up with a precise statement of
>the problem to be solved and the characteristics of an
>acceptable - not ideal - solution.
I will try to make more measuring and write it more precise, however I
think that the idea of problem is clear (?)
Reply by Vladimir Vassilevsky●September 20, 20092009-09-20
Rune Allnor wrote:
> On 20 Sep, 05:19, Vladimir Vassilevsky <nos...@nowhere.com> wrote:
>
>>Rune Allnor wrote:
>>
>>>On 18 Sep, 20:28, Piotrek �elechowski <pezel...@gmail.com> wrote:
>>
>>>>In few words - It receives sound from room via microphone, filters by
>>>>pass band filter (tuned on resonance frequency of room) and
>>>>transmitting via speaker sound in opposite phase.
>>
>>>...
>>
>>>>So I am looking for some structure/algorithm which help to correct
>>>>phase in full pass band (it must have opposite phase characteristic to
>>>>characteristic of filter to provide constant phase).
>>
>>>The problem is that the 'true' source and your cancelling
>>>source are located at different positions,
>>
>>Dr. Rune, cancellation is a different problem, which is indeed
>>difficult. However the OP is talking about the active damping of the Q
>>of the room. At low frequencies, the room acts as a cavity resonator.
>>You only have to damp the most pronounced resonant modes; this is quite
>>feasible.
>
>
> How is 'damping' different from 'cancellation'?
You only have to consider few modes of the lowest orders, you don't
worry about the interference pattern, the criteria is the gross energy
rather then SPL at particular location.
Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com
Reply by Rune Allnor●September 20, 20092009-09-20
On 20 Sep, 05:19, Vladimir Vassilevsky <nos...@nowhere.com> wrote:
> Rune Allnor wrote:
> > On 18 Sep, 20:28, Piotrek �elechowski <pezel...@gmail.com> wrote:
>
> >>In few words - It receives sound from room via microphone, filters by
> >>pass band filter (tuned on resonance frequency of room) and
> >>transmitting via speaker sound in opposite phase.
>
> > ...
>
> >>So I am looking for some structure/algorithm which help to correct
> >>phase in full pass band (it must have opposite phase characteristic to
> >>characteristic of filter to provide constant phase).
>
> > The problem is that the 'true' source and your cancelling
> > source are located at different positions,
>
> Dr. Rune, cancellation is a different problem, which is indeed
> difficult. However the OP is talking about the active damping of the Q
> of the room. At low frequencies, the room acts as a cavity resonator.
> You only have to damp the most pronounced resonant modes; this is quite
> feasible.
How is 'damping' different from 'cancellation'?
Rune
Reply by Rune Allnor●September 20, 20092009-09-20
On 20 Sep, 01:59, Piotrek =AFelechowski <pezel...@gmail.com> wrote:
> >>Jerry
> >How wide is the band whose phase you want to shift?
>
> It depends of room acoustic. Let's say, for example, about 5Hz @ -3dB
>
> > Have you calculated the phase shift from one end of the room to the
> > other?
>
> It depends of between which walls. But it doesn't matter now.
>
> > (Pure delay is easy to arrange. Constant phase shift implies
> > delay that varies inversely with frequency.)
>
> I know. That's why I'm asking for phase corrector. Phase shifter made
> on a delay can adjust phase in a middle of pass band but is useless to
> correct phase in a whole pass band.
>
> >>Rune
> >How did you test that?
>
> I made couple of analysis by 'Room EQ Wizard'
You really did your homework, then.
> >With wide-band signals you end up with exactly the kinds of
> >problems you see.
>
> My device doesn't work in wide-band (it has narrow pass band filter
> inside).
> I agree with You that it won't work perfectly in whole room, but for
> example for 30Hz +-45degrees of phase shift give You almost 3meters in
> direct of wave. Beside, wave length is longer than room dimensions so
> some rules are different than for higher frequencies. Please, don't
> worry about area, because even in one reference point - main problem
> is to get close to constant phase characteristic in pass band of
> filter.
Well, I don't worry about area (or volume). You should.
> >Do this step by step: First obtain canceallation in one point.
> >Then extend the area of cancellation.
>
> Ok. So I need phase corrector to avoid problem which I wrote about on
> the beginig of discussion.
The first step is to come up with a precise statement of
the problem to be solved and the characteristics of an
acceptable - not ideal - solution.
Rune