Speaker Phase

[Arai Yuichi]

Hi, My name is Yuichi Arai

Regarding SPL/Phase measurement, I like to know the way to have a correct phase plot.
In case I put t=o at IR peak, then the phase plot must be correct. I believe this compensate the sound fly time from the speaker to the mic.
On the other hand, there is a Minimum phase button in the bottom of the screen. Does this also the sound fly time offset?
If so, both two phase graphs display the same? In my case, these are different.
Anyone explain the difference between the two method?

Thank you in advance.

 

[Matthew J Poes]

Hi, My name is Yuichi Arai

Regarding SPL/Phase measurement, I like to know the way to have a correct phase plot.
In case I put t=o at IR peak, then the phase plot must be correct. I believe this compensate the sound fly time from the speaker to the mic.
On the other hand, there is a Minimum phase button in the bottom of the screen. Does this also the sound fly time offset?
If so, both two phase graphs display the same? In my case, these are different.
Anyone explain the difference between the two method?

Thank you in advance.

Is this a question specific to REW? If so we should move this page to the REW forum so John can answer.

However to answer your question, the impulse is just a recording and so the impulse won’t exist in the recording until it hits the microphone. The fly time you mention is automatically accounted for via physics. The impulse timing issue has to do with other issues that John can answer better. I believe that to take measurements with precise locked impulse response timing such that every measurement is the same you need a loopback. John offered the option to use another speaker for this, in which case it can measure the fly time, and compensate. This ensures every measurement is the same, from a timing standpoint. This approach wouldn’t make sense for crossover design. You want to use a loopback.

Having said that, the phase is correct for a given measurement, it’s more about comparing Across measurements. This is important of course since a crossover design requires that you take quite a few measurements.

 

[Arai Yuichi]

Is this a question specific to REW? If so we should move this page to the REW forum so John can answer.

However to answer your question, the impulse is just a recording and so the impulse won’t exist in the recording until it hits the microphone. The fly time you mention is automatically accounted for via physics. The impulse timing issue has to do with other issues that John can answer better. I believe that to take measurements with precise locked impulse response timing such that every measurement is the same you need a loopback. John offered the option to use another speaker for this, in which case it can measure the fly time, and compensate. This ensures every measurement is the same, from a timing standpoint. This approach wouldn’t make sense for crossover design. You want to use a loopback.

Having said that, the phase is correct for a given measurement, it’s more about comparing Across measurements. This is important of course since a crossover design requires that you take quite a few measurements.

 

[Arai Yuichi]

Hi, Mr. MjPoes

Thank you for your response. Yes, my question is on the REW platform. In case this must be addressed to other page, Sorry.
Please transfer this message to John in this case.
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Basic question is how to measure the correct [phase property] of the speaker system.

I obtained TSP signal thru the DUT speaker and the mic. Then, t=o set at IR peak. This means that the sound fly time is removed. So, The Phase must be displayed correctly, I think. It looks working.
My question is that [this phase curve] and [Minimum phase curve] which is generated by [Generate minimum phase button] does not match. Not a small difference.

I have adjusted IR window setup with several ways.So, which is correct? is my question.
I have some misunderstandings, I guess.

Yuichi

 

[Matthew J Poes]

Hi, Mr. MjPoes

Thank you for your response. Yes, my question is on the REW platform. In case this must be addressed to other page, Sorry.
Please transfer this message to John in this case.
------------------------------------------------------------------
Basic question is how to measure the correct [phase property] of the speaker system.

I obtained TSP signal thru the DUT speaker and the mic. Then, t=o set at IR peak. This means that the sound fly time is removed. So, The Phase must be displayed correctly, I think. It looks working.
My question is that [this phase curve] and [Minimum phase curve] which is generated by [Generate minimum phase button] does not match. Not a small difference.

I have adjusted IR window setup with several ways.So, which is correct? is my question.
I have some misunderstandings, I guess.

Yuichi

Everything is ok, the post has been moved. Hopefully John will see this and chime in. He may understand what you want/need better than I and be able to provide better information.

 

[Arai Yuichi]

Mr. MjPoes

I appreciate your action.
Thanks a lot.

Yuichi Arai

 

[John Mulcahy]

Easiest is to use the Estimate IR Delay option in the graph controls and let REW remove its estimate of the time delay in the measurement. The minimum phase response is something different, that is a signal which has the same amplitude response as your measurement but the minimum energy delay. It will have a different phase response, you can read more about minimum phase here.

 

[Arai Yuichi]

Thanks a lot, John　　　Yuichi