Subwoofer Distance

MultEQ doesn't actually measure distance. It measures signal delay. That delay is due to the time it takes for sound to travel to the mic in air PLUS the electrical delay in the signal inside the sub. Any type of filter in the sub introduces delay. Also, any type of dsp processing in the sub introduces delay. So, it's quite normal to see longer "distances" reported for the sub. You should leave it as MultEQ found it. 

It's when the reported distance is shorter than the physical distance that we worry. Something else causes that, usually vibrations that travel to the mic via a solid surface (e.g., the floor). Sound travels faster in solids than it does in air and this can cause the short readings.  The first thing to try is to make sure that the mic is isolated from any vibrating surfaces. 

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2 Comments

  • 0
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    Nicholas Chee

    Thanks for this Chris - I was just looking for the right thread to post this in.

    I am using the MultEq calibration system in my Marantz SR6003 AVR. My powered subwoofer, Monitor Audio RSW 12, is connected to the single LFE output of the AVR using a Y-stereo RCA connector. During calibration, the frequency control of the subwoofer is disabled (i.e. controlled by the AVR's bass management system).

    My question is in relation to the differing distances reported by Audyssey for my subwoofer when the phase control of my subwoofer is set at 0' (about 6 metres) vs. 180' (about 4.5 metres). I have gone with 0' since that is what you have recommended as a default option on the other thread but I am just curious if this difference is expected, and whether I should select 180' since the distance is closer to the physical distance (about 4 metres).

    As an aside, Audyssey reports the subwoofer channel as "REV" randomly after the initial test sweep no matter whether phase control is set at 0' or 180' (i.e. sometimes it is not reported at all and sometimes it is for the several times I have tried calibration). Not sure if this is a related issue.

    Would be extremely grateful for your kind thoughts on the above.

    Cheers,

    Nick

  • 0
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    Chris Kyriakakis

    Hi Nick,

    The so-called phase control on the back panel of the subwoofer is a simplistic analog control that only changes the phase at one frequency.  Proper phase alignment requires that the phase change is different at every frequency, but this is not possible with an analog control.  So, our recommendation is to leave it at 0.

    The reason MultEQ sees a longer distance than the physical distance is because of the filters in the electrical path of the signal or perhaps because of the interaction of the woofer and port in your sub.  This interaction can also cause polarity reversal warnings.  If the sub is properly connected, then you can simply ignore the warning.  It has no effect on the calculated MultEQ filter.

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