After years, I finally got my subwoofer hooked back up. Unfortunately, all my crossover knowledge has completely left me. Currently, my center, fronts, and surrounds are set to 80hz, which I've heard is the standard. Fine. My question is...what should I set the subwoofer (it's a passive one, if that makes a difference) to ? Most places I've been reading say that you should put it at 10hz or so more than the speakers' crossover setting. Is this true ?