OTHER TECH

If you're concerned about sound quality at several listening positions as opposed to just one, you should definitely consider using multiple subwoofers. Adding a second sub helps to even out the room response over a larger area than just a single seat. The most common method of adding a second sub is to place it opposite your first one (that is, across from the first sub on the opposite wall).

But this traditional formula has recently been modified based on Dr. Toole's research. He recommends placing the subs in the middle of the front and back walls. (THX recommends placing them in the middle of the left and right walls.) Toole's method requires some equalization to flatten the bass response so all the seats in the primary listening area hear solid, even bass. My own experiences have shown that you can get excellent results by using a high-quality twelfth-octave equalizer and two good subs. To get an even more consistent bass response over a large seating area, move up to four subs. (Why not three? Because symmetry is key to making this work. Every sub needs to have a counterpart placed in the opposite position.)

Four subs have been used as recommended solutions in demo rooms by THX, the Home Acoustics Alliance (HAA), and others. At CEDIA Expo 2006, HAA's Gerald Lemay set up two identical rooms, one with a single sub in an uncalibrated space and another with four subs with EQ in a calibrated space. The goal was to show what a properly calibrated home theater sounds like compared to the typical drop-it-in-place setup. The idea of buying three more subs might be daunting, but the results were impressive.

As with two subs, the recommended placement for four subs is to put one in the middle of each wall. If a door or some other obstruction prevents you from placing a sub right in the middle of a wall, the four corners of the room are acceptable as a secondary location.

As with two subs, you'll need to use good-quality EQ to get the best results with four. Unfortunately, calibrating subwoofer EQ by ear isn't really an option. If you've invested in the gear for a two- or four-sub system, consider contacting someone with the proper equipment to tune your setup. The Home Acoustics Alliance (homeacoustics.net) has listings of local certified technicians who can provide the necessary expertise, or contact an HAA-certified CEDIA installer (cedia.net).

Sean Greer is the owner of and senior design engineer at Experience AV Home Theater (ExperienceAV.com) in Montrose, Colorado.

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