The “Bass Management Boot Camp” article about subwoofer setup that I wrote for the November S+V inspired an in-turn inspiring e-mail from reader Bruce Erwin. Bruce recalled his days setting up sound systems when he’d use a 1.5-volt battery to test subwoofer phase. If the sub and main speakers were in phase, he’d hear a single thump when he connected the battery to the wires leading to the sub's terminals. If they were out of phase, he’d hear a double thump.
That’s with passive subwoofers, though. Almost all of today’s subs have built-in amps, so this method wouldn’t quite work with them. Still, it got me wondering if I could come up with a simpler phase check than the ones I suggested in the article, which required either measurement or careful listening. My e-mail convo with Bruce gave me some ideas and, ultimately, a method that’s simpler than my original. And all you need to do it is a piece of free software and a meter you’ve either already got or can get for nothing.