# Phase switch and audyssey xt32



## Dwight Angus (Dec 17, 2007)

I have dual PB13 Ultras and ran some REW tests that showed a big dip at the 70 hz crossover. I corrected the problem by making adjustments to the phase switch on both subs. My preamp is Onkyo 5508 and includes XT32.
Should the dip be corrected by making physical phase adjustments on the subs or should they be handled through Audyssey's XT32 bass management process? Also what is the downside of adjusting phase as it seems I have lost some of the slam after changes were made?


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## theJman (Mar 3, 2012)

I'd go with the EQ adjustment over a phase adjustment. The EQ is balancing out the sound in specific places for your particular situation, as opposed to the phase adjustment which is altering the subwoofers total output profile. Think of EQ as a surgical repair, where phase is more like a chainsaw approach. :yikes:


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## wgmontgomery (Jun 9, 2011)

In your post you stated, "...showed a big dip at the 70 hz crossover." If you have the crossover set at 70Hz, there SHOULD be a big dip (in bass from the sub). Just to make sure, what crossover settings are you using? This may very well explain the dip.


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## Dwight Angus (Dec 17, 2007)

The crossover setting is 70 hz for the mains. I ran a 70 hz sine wave and adjusted the phase setting to find the loudest volume for both subs. One sub showed no increase so I left the phase setting at zero. The other sub showed an increase of 6 db increase from 74.6db to 80.9 db increasing the phase to 1 o'oclock.


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## wgmontgomery (Jun 9, 2011)

Are the subs also crossed-over at 70Hz? Your SSP and the subs have their own settings; you usually bypass (as in, "don't use") the sub's crossover and let the SSP/AVR determine the crossover point. 

If you are seeing a dip at 70Hz it could simply be the crossover settings. For example, you stated that the mains are crossed over at 70Hz; if the subs are set for ~60-50Hz you WILL see a pretty big dip. I'd double check the crossover points for the subwoofers on the subs AND the SSP. Just a thought... onder:


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## tonyvdb (Sep 5, 2007)

Agreed, if your using the crossover knob on the rear of the sub as well as the receivers settings your basically adding a much more dramatic drop off at the crossovers setting. Make sure that the subs crossover is off or turned all the way to its highest setting (usually 120Hz).


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## jmschnur (May 31, 2011)

Dwight Angus said:


> I have dual PB13 Ultras and ran some REW tests that showed a big dip at the 70 hz crossover. I corrected the problem by making adjustments to the phase switch on both subs. My preamp is Onkyo 5508 and includes XT32.
> Should the dip be corrected by making physical phase adjustments on the subs or should they be handled through Audyssey's XT32 bass management process? Also what is the downside of adjusting phase as it seems I have lost some of the slam after changes were made?


Best to change the distance of the sub using REW to monitor the effect. I would leave the phase at 0 for both and go through xt32 calibration. Then run REW and adjust the distance of one sub to best value then the other.

I believe the process is described in the FAQ for Audyseey in the AVS forum.


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## Dwight Angus (Dec 17, 2007)

The crossover in the avr is set to 70 hz. The crossover on the subs are set to 120 hz


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## Dwight Angus (Dec 17, 2007)

Thanks jmschnur I read the FAQ on this topic at AVS and it sounds exactly like the problem I am having. I am going to reset the phase to zero on the one sub and rerun xt32 setup and then adjust sub distances to get the best results around the xo area and measure with REW. I will post the results as soon as possible. Cheers.


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## Dwight Angus (Dec 17, 2007)

After running the audyssey setup I changed the distance on the 2nd sub by a foot and measured with REW until I found the distance that gave me a flatter response. Had to add 5 feet to get a flat response. I guess Audyssey doesn't correct speaker sub issues around the xo.


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## jmschnur (May 31, 2011)

Dwight Angus said:


> After running the audyssey setup I changed the distance on the 2nd sub by a foot and measured with REW until I found the distance that gave me a flatter response. Had to add 5 feet to get a flat response. I guess Audyssey doesn't correct speaker sub issues around the xo.


Its current algorithm does not seem to be correct for two subs. How close to you get with the distance tweak?


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## jmschnur (May 31, 2011)

jmschnur said:


> Its current algorithm does not seem to be correct for two subs. How close do you get with the distance tweak?


By that I mean, does the tweak work well.


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## Dwight Angus (Dec 17, 2007)

The tweak works very well. I now get a nice flat response from both subs at the xo. Thanks for the "heads up"


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## Dwight Angus (Dec 17, 2007)

jmschnur said:


> Its current algorithm does not seem to be correct for two subs. How close to you get with the distance tweak?


Yeah from what I have read the algorithm is capable but unable to due to where the AVR manufacturers insert it.


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