Posted by Wayne Parham on May 23, 2003 at 23:21:33

In Reply to: need expert advice ( and epstein too ) posted by replay on May 23, 2003 at 19:32:40:

There's no way to know without modeling and/or empirical testing. The proper implementation of subwoofer crossover depends more on the environment than anything else.

Outdoors, you want the subs close together and close to the mains, if possible. The idea is to keep the sound sources within 1/4λ, and so you would pick your crossover frequency low enough to make that happen.

Indoors, it's a whole different ball game. The reflections from walls make lots of virtual sources, many of which are further than 1/4λ. This forms standing wave nodes that make hot and cold zones in the room at various bass frequencies. The best thing to do it to distribute sound sources to form dense interference, averaging the sound field in the room.

You don't want to crossover the subs as much as you want to blend them, the more you have the better it will be. You'll want to place the subs fairly far apart and provide as much bass overlap as possible, up to 300Hz. The trade-off is sound can be localized above about 100Hz, so you don't want a subwoofer placed far away from the mains that is running all the way up to 200Hz or 300Hz. This is a situation of competing priorities. Move the subs further from the mains and run them higher in frequency to smooth room modes, closer and lower to reduce localization problems. You'll have to do some experimentation to find the best combination of subwoofer positions and low-pass frequency and slope.