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Linear Phase without FIR
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LeruSound View Drop Down
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    Posted: 12 September 2017 at 7:54pm
Hello guys, i have that response from a 3 way cab, phases are perfectly aligned.
But i'm having 3 rounds of phase in the whole band, guess this is giving me some blurred sound.
I would like to achieve a linear phase, and i would use a xilica XP to do that. Is it possible to do that with all pass filter or am i just going from bad to worse? Guess i would not achieve any result that way, cuz it's kinda add more filters phasing..
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Read what is phase response and how it is comparing to group delay.
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Would you mind to be more specific please? Do you have any document to link me?
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You cant get straight line in phase response with group delay >0. Or rather if you would the sound would be totally But it doesnt mean something is wrong. Phase(freq)= f*t(freq)*2pi-2kpi

Edited by gen0me - 12 September 2017 at 8:22pm
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Guess i understand what you mean, anyway i would like to improve from 3 full rounds, maybe you misunderstood my straight line concept...
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Logically it looks like i can use all pass filter from xilica, as it shows phase icreasing from 0 deg.. That would fit to my response in both REW and SMAART, where phase is decreasing giving my 0 reference to the top end freq, thus the faster (CD horn). But still something doesn't convince me.. (i'm now switching from BSS 336T to Xilica, so i'm not able to try now, so i'm trying to predict if i'll be able to fix this then)
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On 2.4ms one clearly the top of bandwidth changes phase slower then bottom. Around 160hz at bottom phase changes fast due to large peak on the group delay response. This is very untypical design with one horn for all bandwidth. With few horns it could happen few times.

Edited by gen0me - 12 September 2017 at 9:09pm
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Originally posted by LeruSound LeruSound wrote:

Logically it looks like i can use all pass filter from xilica, as it shows phase icreasing from 0 deg.. That would fit to my response in both REW and SMAART, where phase is decreasing giving my 0 reference to the top end freq, thus the faster (CD horn). But still something doesn't convince me.. (i'm now switching from BSS 336T to Xilica, so i'm not able to try now, so i'm trying to predict if i'll be able to fix this then)





You're chasing your tail! The phase wraps are a result of the physical distance between mic and speaker. YOU CAN'T GET RID OF THEM. PERIOD.
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Wait, what you mean? My measurement is tracked with compensation delay, as u can see, the final part where the crossover is not acting is straight..
Am I wrong?
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Originally posted by LeruSound LeruSound wrote:

Wait, what you mean? My measurement is tracked with compensation delay, as u can see, the final part where the crossover is not acting is straight..
Am I wrong?


Hi Leru, your not wrong, phase wrap due to delay looks as in the screen shots genome has posted.
Do you have the xilica that does FIR? An IIR allpass filter response would go the other way and would not unwrap IIR filter phase.
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So as I thought, allpass filter would just increase phase shifting, isnt it? Now I have no time, later ill get a better look to the delay topic ad it is not completely clear yo me..
I have 5 filters acting there, all are 4th order except the higher one is passive 3th order fixed around 2.7 kHz, so allI phase shifting to me is logically because of filter action. Then theres a delay to realign the bottom 150-900hz speaker to the higher. But everything looks like its a result of filter phase shift..
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Originally posted by bob4 bob4 wrote:

Originally posted by LeruSound LeruSound wrote:

Logically it looks like i can use all pass filter from xilica, as it shows phase icreasing from 0 deg.. That would fit to my response in both REW and SMAART, where phase is decreasing giving my 0 reference to the top end freq, thus the faster (CD horn). But still something doesn't convince me.. (i'm now switching from BSS 336T to Xilica, so i'm not able to try now, so i'm trying to predict if i'll be able to fix this then)





You're chasing your tail! The phase wraps are a result of the physical distance between mic and speaker. YOU CAN'T GET RID OF THEM. PERIOD.


even if you were to get a system with flat phase, if you then moved the measurement mic further away you would measure a phase with constant slope. so constant slope is as good as you can get - getting it horizontal at an arbitrary measurement position isn't any better.


Edited by snowflake - 13 September 2017 at 11:14am
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