# setting subwoofer phase without REW, only with dB meter



## THX-UltraII (Nov 19, 2008)

I have a dB meter and want to find the right phase setting for my subwoofer. Am I correct that I can do this by:

- Run my front speakers on +-75dB with a 80Hz test tone.
- Disable the front speakers and put the subwoofer on a volume that results in +-75dB also with 80Hz test tone.
- After this run both subwoofer and main speakers and adjust the phase rotation button of my subwoofer and find the value on my dB meter that gives me the HIGHEST result.

Thanks.

My setup:
Marantz SR5005
Teufel Theater 8 5.1 THX-UltraII
dB-meter: http://www.elektro-rama.nl/contents/nl/p1201.html


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## drdoan (Aug 30, 2006)

That could work. One caution-don't play the test tone too long, just long enough to get a reading. Pure tones are pretty hard on speakers. Have fun. Dennis


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## wgmontgomery (Jun 9, 2011)

I've been chewing on this question since I first saw it; I agree that it _could_ work and _seems_ logical. I will try to check it out on my system today (I need someone to change phase while I check the meter) and report my results. Since my system is already "tweaked," any change should to obvious.

BTW-is the phase control on your sub a simple 0°/180° switch or a continuously variable knob?


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## drdoan (Aug 30, 2006)

mine is digital and continuously variable, but, I don't use it because I use the Audyssey Sub EQ to balance my subs. Dennis


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## phazewolf (Feb 5, 2012)

Correct me if I am wrong but sense it sounds like he is using a avr would you not just set the distance and leave the phase alone?


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## drdoan (Aug 30, 2006)

I still might be a good idea to set phase, as it isn't unusual for a sub's distance to be set farther back than the actual physical distance to the speaker to achieve the proper balance. Most speaker alignment procedures will set the sub at a greater distance than the main speakers, thus possibly creating phase errors. However, many auto speaker setting software will correct phase as part of their alignment procedure.


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## phazewolf (Feb 5, 2012)

When I see that it sets the distance different then the real number it is because it is accounting for delay from the sub amp.


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## wgmontgomery (Jun 9, 2011)

phazewolf said:


> When I see that it sets the distance different then the real number it is because it is accounting for delay from the sub amp.


Do you mean the delay from auto power? Some subwoofers have on-board eq than can also throw-off the auto calibration, and _simple_ (??) room acoustics can also confuse the auto eq. Auto calibration is a great thing, but it is neither perfect nor infallible.

I did not have time to check my system today, but I will try to do it Wens. and report back with my findings.


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