# REW: how to figure proper phase/distance setting for subwoofer



## artinaz (Jul 31, 2008)

hello I have my dual subs located in front along the line of my left and right mains- phase is set to zero. When I run the automated calibration for my processor (Emotiva UMC-1) it sets the subwoofer distance at 25ft instead of the 10ft that it is and I do get a smoother response too in REQ. I assume that the UMC-1 is setting the distance higher to compensate for the phase.

Since v5 now has the phase displayed in the main window along with the frequency response, is there an easy way to calculate the proper phase setting around the crossover frequency of 80hz ? I would rather be able to calculate the setting instead of having to take multiple readings by varying the phase setting.


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## JohnM (Apr 11, 2006)

Getting sensible phase measurements can be tricky, you need a loopback as a reference and need to take account of the transit time to the mic, and even then it is a difficult way to decide what to do. The best method would be to use the RTA and make your adjustments while you watch the effect on the RTA. Use REW's "Pink PN" test signal, set the RTA for Rectangular window, no averaging, 64k RTA length. Measure with the sub and one main speaker running. Try phase at 0 and 180 degrees to see which gives the smoothest response through the crossover region, then fine tune by varying the distance setting.


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## mc_lover (Aug 25, 2012)

Dear JohnM, 
Your explanation helps a newbie like me.

Could you please explain a bit more on why we do a measurement just a subwoofer + *JUST ONE speaker*?
Thank you


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## audioelements (Dec 25, 2007)

Because there would be two different arrival times at the measurment mic.


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