Aligning Driver Phase - REW v5 Example - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #11 of 17 Old 01-27-11, 06:43 PM Thread Starter
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Re: Aligning Driver Phase - REW v5 Example

Maverick (and also Jason further above),
Thank you both for your interest and kind comments.

I tried to include the major steps, but there may not be enough detail included. If you get into this later and have specific questions, I will try to help out.
Enjoy!
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post #12 of 17 Old 01-29-11, 06:35 AM
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Re: Aligning Driver Phase - REW v5 Example

Quote:
> Since the phase error at the target XO is almost 180 deg, letís first just invert the polarity of the MR to see what happens. I donít see a facility do this in REW for an existing measurement so letís use the DCX to invert the driver signal and then measure again.
Use the "Invert Impulse" control in the Impulse window.
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post #13 of 17 Old 01-29-11, 07:51 AM Thread Starter
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Re: Aligning Driver Phase - REW v5 Example

Thanks! I see it now - right where it should be!
Great program!
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post #14 of 17 Old 05-27-11, 10:09 AM
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Re: Aligning Driver Phase - REW v5 Example

Could you tell me what settings you had for measuring the delays between the speakers? I'm wondering about the Analysis section under preferences. What did you have set for the Impulse response window defaults? Because I'm not getting one nice peak like you have in your graphs.
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post #15 of 17 Old 05-27-11, 06:26 PM Thread Starter
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Re: Aligning Driver Phase - REW v5 Example

It was not necessary to set a special IR window using this method in my particular situation. The default automatic window worked fine. My speaker was on a stand with the floor being the nearest boundary about 0.8 m away and the XO was around 2 kHz. Under those conditions the 1 m mic distance is close enough that multipath was not a problem.

If you are in a small room and your speaker is nearer to a boundary then there may be more of a problem. An IR window can help in that case. The left settings needs to be just before the initial start of the impulse (0.2 ms to 0.5 ms) and right setting should be long enough to capture a measurement an octave below the lowest part of the XO range you are interested in. In my case of an 800 - 5k Hz XO range I would like to see to see data down to about 400 Hz so a right setting of about 2.0 ms or greater would be okay.

The lower the XO, the more difficult it will be.
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post #16 of 17 Old 03-23-18, 01:14 AM
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Re: Aligning Driver Phase - REW v5 Example

Hi Jtalden,
I have read the post, and I am new on REW. I try to simulate the Impulse response like yours in the post( I am trying to get the phase data to calculate delay),

but I only get a peaking data without the sine wave

I use the JRiver's WDM driver to be my loopback method so the REW measurement setting I use "Use loopback as timing reference"

(I can not post the image so be sorry to use word to explain my question or if I can use the gmail to explain my environment to discuss with you.)

any setting that I missed? I can not get the similar result like yours

please help
thanks!
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post #17 of 17 Old 03-23-18, 11:12 AM Thread Starter
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Re: Aligning Driver Phase - REW v5 Example

Quote:
Delight5566 wrote: View Post
Hi Jtalden,
I have read the post, and I am new on REW. I try to simulate the Impulse response like yours in the post( I am trying to get the phase data to calculate delay),

but I only get a peaking data without the sine wave
I'm not clear on the problem your discribe, but If you ran a sweep measurement and the impulse shape is very different from mine then check to see that the impulse graph is set to '%FS' and not 'dBFS'. The control appears in the top left corner of the graph when the mouse is hovered there - See REW Help for the impulse chart.

Quote:
I use the JRiver's WDM driver to be my loopback method so the REW measurement setting I use "Use loopback as timing reference"
I would expect that will work correctly. You can confirm it is by taking 3 repeated sweep measurements and checking the impulse overlay chart to confirm that the 3 impulses are identical and lay directly on top of each other. If there is any shift between them (when zoomed in all the way) then there is a problem. They all should be shifted away from 0 ms by the same xx.xx ms amount.

Quote:
(I can not post the image so be sorry to use word to explain my question or if I can use the gmail to explain my environment to discuss with you.)
I prefer to help you here as others may benefit at well. You can use the post padding thread to create 4-5 quick posts. That will then allow you to post charts and mdat files in this thread to explain the situation.

Quote:
any setting that I missed? I can not get the similar result like yours
If the '%FS' setting is not the solution, please post a chart showing the problem.

Comments:
This process work very well for XOs in the midrange and above (above the modal region). If this is a SW XO <300 Hz the room modes can make it very difficult to use. Other SW XO timing methods are likely much easier to do and provide similar results.

Given the needed mdat measurements, I can provide you with a timing recommendation that you can use to confirm your results.
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aligning , dcx2496 , driver , impulse , phase , response , rew , xover

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