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Phase Swith and Low-Pass Filter on Sub?

379 Views 2 Replies 3 Participants Last post by  Aerlith
I posted this in another forum and thought this one better.

Can someone give me (or direct me to) an explanation (hopefully better than the manual) as to the functions of the Phase Switch and the Low-Pass seettings on my B&W ASW1000 sub?

I have just finished setting up my HT and since I have an odd shaped room, I am trying to optimize my settings and don't fully understand this. I have 603S2 mains, 601S2 surrounds and a center. Manantz SR700 rec.

The system is used for 50% HT and 50% Music.



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The phase switch switches the phase http://www.avsforum.com/ubb/smile.gif . This effectively reverses the positive and negative terminals coming into the sub. Depending on the sub the input may be a RCA connector and there is no other way to reverse the phase. Ideally you want the phase to be the same as the phase as your other speakers. Although depending on the location of your sub in relation to your other speakers it might sound better out of phase. The best way to do this is to sit in the optimum listening position and have someone flip the switch and see which sounds better. It is better to do this with a test tone than actual music or soundtrack.

The low-pass setting selects the frequency at which the sub-woofer kicks in. If you have large front/center/right speakers (8" or larger bass speakers) then the low-pass selector should probably be in th 80-100hz range. If your other speakers are smaller then increase the crossover frequency into the 100-120hz range.

-- Craig
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The phase switch should indeed be set by ear, as it effects the transition from the sub to the other speakers where their frequency responses overlap. A useful set of 1/3 octave "tones" can be found on the Stereophile test disc 1. The phase swich position resulting in more bass is the correct one.

As far as the low-pass filter on the sub, if you are using the Marantz receiver's built-in crossover (front speakers set to "small") then you will want the sub's filter "out of the way" as much as possible (cascading filters can lead to a sonic mess!). Turn the crossover to it's highest position.

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