Quote:
Originally Posted by jdandy
aqman.......The JL Audio Fathom and Gotham subwoofers have a phase control that allows the user to adjust timing of the subwoofer output relative to the mains speakers. The phase angle is adjustable from 0° to 280°. This allows a user to synchronize the subwoofer cone's launch time with the mains speakers. One of the easiest ways I have found to make this adjustment relatively accurate is to reverse the polarity of the main speakers, usually by swapping the positive and negative speaker wires at the back of the speakers. Set the subwoofer crossover to 80Hz for testing purposes and adjust the subwoofer output to equal the main speakers as close as possible. Using music with solid low and mid-bass content or as an alternative use low frequency bass test tones while making minor adjustment to the Fathom's phase control. When you reach the point where the least low frequencies are audible you will have the woofers in the mains speakers and the subwoofer launching at the same time. In other words, with the mains out of phase with the subwoofer both speakers will cancel the low frequency outputs when the phase control reaches the right spot. This may take some time to dial in accurately. It is advisable to have someone help you to make the adjustment on the phase control while you sit in the sweet spot listening. Once the bass output is the least it can be stop there, then reverse your mains speaker's polarity back to the proper positive and negative connections from the amplifier and you are done. After that it is a matter of selecting the specific crossover point you want to use and adjusting the output level to your satisfaction.
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That procedure that you listed is similar to the one described by Barry Ober in the white paper that the OP linked to/referenced above. I just went through this procedure with my system. It works very well.