Dual Mirage BPS400 Subwoofers
Dear Gary: I just bought my second Mirage BPS400. My receiver only has one subwoofer output on it. My questions are: 1. What’s the deal with splitting the signal from one sub output into two subwoofers? Degradation of signal? Loss of signal? Is this a good or bad idea? 2. Can these two subwoofers cancel each other out? I have both subwoofers up front, and the woofers are facing each wall on either side with the TV in the middle. I need help with this, and can’t seem to find anyone who knows these answers.
Craig Alexander Lorden
Managing Editor Perry Sun Comments:
The subwoofer output, as well as other preamp outputs from your receiver are of very high impedance, so splitting the signal into two will not have a deleterious effect. You can get a reduced effect from two subwoofers due to phase cancellation, and this depends, amongst many factors, on their placement, the presence of wall boundaries, and the position of the listener in the room. Just about all subwoofers these days have adjustable phase control, whether switchable between 0 and 180 degrees, or continuously variable, to help you compensate for phase-related attenuation of in-room bass response. Your BPS400 does not have phase control. Therefore, you should try to optimize the placement of each subwoofer in your listening room. (In fact, I would recommend this as the first measure before electronically adjusting phase.) You just need to set up the subwoofers at your initial desired locations, and then if necessary, experiment with their placement to get the optimal combination of smoothness and output. An approach to this could be to place one of your subwoofers where the listening position would be. Then, crawl around the room and listen at various locations for apparent low-frequency response. The locations that provide the best combinations of smoothness and output are likely candidates for where you finalize the location of the subwoofers. You should then listen carefully to the performance of the two subs at these locations, to verify that you’re hearing deep bass with greater energy (than one sub) that is reasonably smooth. The AVIA Guide To Home Theater DVD has some very good test signals for evaluating in-room response from subwoofers. Good luck
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