"Best" subwoofer crossover frequency

[Stu-r]

Just thought I'd share this. I've been listening to stereo music and home-theater for about 50 years. I've always set the subwoofer crossover based on the other speaker low-frequency cutoffs or the "recommended" crossovers (90hz for Yamaha receivers, I understand Noussaine recommends 120-130hz, etc). But lately, the sound I've been getting has been irritating.

I finally found the problem and corrected it. Because of room limitations, my subwoofer is located next to one of my mains, which means it must be set in phase with that main. My center is about six feet from that main. There seems to lie the key. At 80-90hz (a commonly used crossover frequency), the sub is 1/2 wavelength from the center. 180 degrees out of phase, and uncorrectable at that frequency because of the need to maintain phase with the mains. The solution was to choose a crossover equating to one full wavelength at the distance from the center speaker.

Although the crosover frequency doesn't look intuitively good, the interference effects are gone and everything (classical, vocals, and HT) now sounds great. If you want to try this, divide 1100 by the distance in feet between your center and subwoofer. That will give you the frequency equal to one full wavelength at the distance between them. If you don't select a lower crossover frequency, the interference effects between them will be minimized. In my case, the ideal is 173hz. The closest I can get to 173hz crossover on my HT receiver is 150hz. But that's close enough. You may also have to recalibrate the subwoofer level if the sub isn't particularly flat at its room location.