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

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post #1 of 8 Old 05-22-19, 10:14 PM Thread Starter
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Using REW to adjust subwoofer phase.

I was just thinking (scary...) it might be useful to be able to adjust sub integration in real time. What I mean is to have the mic at the listening position, your computer running REW near the sub, send 10-250hz pink noise through the appropriate channel(s) covering the speakers you are trying to match with the sub and the sub. REW would then have a real time graph, perhaps a bar chart with 24 bars per octave that you could monitor as you fiddled with the phase control on the sub.

Does something like this exist in REW and I am not aware of it?

Is it a reasonable idea?

I could do something similar with a sound analyzer app on a tablet, but the mic in the tablet isn't calibrated and I couldn't easily have the mic in the listening position while fiddling with the phase control. Perhaps I could cast the app to the TV, but still I have no idea how good the mic in the tablet is.

Right now I run a REW analysis pass, adjust the phase and run again, until I get tired of fiddling or it looks good.

One of my issues is I actually have a sub, and then my DIY mains each have an OB woofer cabinet with a "sub amp" driving the woofers so I have 3-8 times the fiddling depending on how pedantic I want to get.

Interested in what others think of my half baked idea.
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post #2 of 8 Old 05-23-19, 09:06 AM
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Re: Using REW to adjust subwoofer phase.

Sure, use pink periodic noise on the generator and monitor the response on the RTA with these settings:

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post #3 of 8 Old 06-02-19, 12:52 AM Thread Starter
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Re: Using REW to adjust subwoofer phase.

Thanks. It worked like a champ.

My mains use a GR Research OB powered woofer cabinet with two 12" drivers powered by a servo controlled plate amp. The mid & tweeter assemblies are of my own "design" which has an L-Pad for the tweeter, so there are a lot of controls which impact the sound. Using the twiddle - test - twiddle method really was not getting things dialed in very well. Using this method I spent about 20 minutes per speaker and voila, it was done.

Now I need to use the same methodology on the Rythmic Audio 15" Main sub dialed to dial it in with the rest of the system.

Thanks again.

Last edited by aceinc; 06-02-19 at 12:55 AM. Reason: grammar
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post #4 of 8 Old 06-05-19, 07:20 PM
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Re: Using REW to adjust subwoofer phase.

Sorry to ask a newbie question but what does a good RTA graph look like when doing this? When do I know my sub phase knob is in the right spot?


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post #5 of 8 Old 06-05-19, 09:19 PM Thread Starter
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Re: Using REW to adjust subwoofer phase.

Remember my use above is a little different than traditional sub integration.

I saw a dip in the frequencies in the 140-200 hz when the phase was "wrong" and as I changed the phase (rotated the phase knob) I was able to see the dip flatten out. I also used the gain control on the plate amp to bring the entire 15-140hz area up to the level of the rest of the "speaker."

When I use it for the actual sub in my system, I expect to see the same results but at lower frequencies. If I can get to it in the next few days, I'll "detune" one of my speakers, do some screen grabs of the graph before & after tuning.
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post #6 of 8 Old 06-05-19, 11:13 PM
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Re: Using REW to adjust subwoofer phase.

That makes sense. Feels too simple!

Would be fascinating to see the screen grabs.


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post #7 of 8 Old 06-06-19, 06:56 PM Thread Starter
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Re: Using REW to adjust subwoofer phase.

Here is an example the first image is out of phase, the second in phase.

https://www.hometheatershack.com/for...1&d=1559865243
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Using REW to adjust subwoofer phase.-wrongphase.jpg  

Using REW to adjust subwoofer phase.-rightphase.jpg  

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post #8 of 8 Old 06-06-19, 09:46 PM
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Re: Using REW to adjust subwoofer phase.

Awesome. Almost TOO easy to see. Thanks.


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