Using REW to adjust subwoofer phase. - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #11 of 18 Old 07-10-19, 10:36 PM Thread Starter
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Re: Using REW to adjust subwoofer phase.

Quote:
FWIW, I did a sweep of the sub by itself and a sweep of each individual main.
I then went into the OVERLAY Phase window and placed the vertical cursor at the SUB/Mains XO point (my case 40HZ).
I then enabled FDW (Frequency Dependent Windowing) and removed smoothing.
I then wrapped and unwrapped all phase plots (mains and sub) so they would be replotted and aligned at the Sub/Main XO point.
I then read the phase of each speaker at the XO point and then used that information to adjust the phase on the sub.
I put the sub's phase half way between my left and right main's phase (split the difference).

This gave me more control than just +/- 180 degrees. The sub is now within @ +/- 8 degrees of each of the mains.

You can then verify the results with a combined sweep to see the summing/nulling/smearing at the XO point.

You can also repeat the procedure to make sure the sub's phase moved in the direction and amount you intended it to (since the sub's phase knobs are usually coarsely marked).

There maybe better ways of doing it, but this is the procedure I used.

HTH
I suspect your methodology is a much more accurate way to do this. However, the patience to execute the iterative process the number of times required to optimize things is beyond my ability.

One note, I did not just flip between 0 & 180 to tweak each woofer cabinet to associated mid/tweeter cabinet, I slowly swept the phase knob through its entire range, monitoring the RTA looking for the flattest response curve. My mains are open baffle with an open baffle amplified woofer cabinet. I did each main independent of the other with the mic about 1 meter (39 inches) from the main. This is what i showed in the graph above (one of the two mains).

I also have a 15" sealed servo sub which I tweaked by putting my measurement mic at the main listening position, sending a full range pink noise signal through the sound processor with all Audyssey off and the "speaker selection" set to fronts & sub. I then fiddled with the various controls on the sealed sub to mesh it with the fronts.

Once everything was complete, I reran Audyssey XT 32 on my sound processor to set everything back up. Sounds pretty good.

Again, your approach may achieve superior results for those with the patience to execute it. My approach seems to yield reasonable results with more immediate gratification.

Last edited by aceinc; 07-10-19 at 10:41 PM.
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post #12 of 18 Old 07-10-19, 10:48 PM Thread Starter
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Re: Using REW to adjust subwoofer phase.

For a single or dual sub system, I would do my testing with the mic at the main listening position.

If you have a sub per main and they are located near the mains I may try the testing both at 1 meter & at the listening position leaving the settings so the sound at the listening position seemed flattest. But this would be mainly to satisfy my curiosity more than anything.
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post #13 of 18 Old 07-10-19, 10:57 PM Thread Starter
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Re: Using REW to adjust subwoofer phase.

One last note, I played with the volume and crossover frequency knobs to get the best results on all 3 plate amps. I found on my OB Mains I needed to fill in some frequencies in the 100-120 HZ range and adjusting the crossover frequency allowed me to do this.

Using the RTA approach really sped up the process, from making a change doing a sweep, analyze the results, and repeat. Doing it the iterative way, my personality is such that after a few passes, my eyes would glaze over and I would finally say, "OK, close enough, Audyssey will fix it."
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post #14 of 18 Old 07-13-19, 01:15 PM Thread Starter
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Re: Using REW to adjust subwoofer phase.

I recently did the tricks above to integrate a pair of Magnepan MMGs with my woofer cabinets. Here is the result;


It is played on an NEC CD Player directly attached to Emotiva XPA-1 (gen 1) Mono blocks. I set up this configuration when I want to hear speakers with the least amount of electronic wizardry "improving" things. I am playing at a rather loud volume and recording straight on to my Samsung S10 phone. The notebook in the foreground is running the RTA from REW. The scale is from 0hz to 20Khz horizontally and 25 DB to 90 DB vertically.
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post #15 of 18 Old 07-16-19, 01:22 PM
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Re: Using REW to adjust subwoofer phase.

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ths61 wrote: View Post
There maybe better ways of doing it, but this is the procedure I used.
Not sure if this is better, worse, or just different, but here is what I came up with (after reading tons of different article and threads). After aligning the subs, I set the crossover on my receiver to 80Hz for the mains and the subs. I disconnected the subs and took a measurement of the center channel at the MLP from 65Hz - 95Hz. This was my reference.

Then, to align the subs to the center channel, I disconnected the center channel and took measurements (also from 65Hz - 95Hz) of the subs and adjusted the phase using the sub distance setting in the receiver.

In the charts below, you can see the phase graph, and the impulse response. The red trace is the center channel, and the other traces are the subs at different distance settings (you can see the distance in feet in the measurement name).

You can see in the charts that the closes phase seemed to be at 43.0', but the closest impulse response was at 41.0', so I split the difference and went with 42.0'.
Attached Thumbnails
Using REW to adjust subwoofer phase.-sub_align_phase.jpg  

Using REW to adjust subwoofer phase.-sub_align_impulse.jpg  


Last edited by cineburk; 07-16-19 at 01:28 PM.
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post #16 of 18 Old 08-08-19, 06:00 PM
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Re: Using REW to adjust subwoofer phase.

How do you do the Frequency dependant windowing FDW? Can't figure it out.
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post #17 of 18 Old 08-08-19, 06:22 PM
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Re: Using REW to adjust subwoofer phase.

Have you checked the settings here?

https://www.roomeqwizard.com/help/he.../analysis.html
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post #18 of 18 Old 08-09-19, 03:48 AM
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Re: Using REW to adjust subwoofer phase.

Quote:
Matthew Burton wrote: View Post
How do you do the Frequency dependant windowing FDW? Can't figure it out.
Just select it on the IR windows dialog.
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