Posted by Wayne Parham [ 32.97.110.142 ] on April 19, 2007 at 11:25:06:

In Reply to: Re: Room modes and speaker placement posted by Duke on April 18, 2007 at 12:04:25:

Your description of the cancellations from reflections is good. That helps people see what's going on. But never forget that the listener's positon is a part of the equation too. No matter where you place a subwoofer, peaks and dips will form within the room. If the listener is in a place where cancellation occurs, he will hear reduced bass levels at that frequency. If he is in a place where there is a peak, he will hear plenty of bass. So if his position is not in the center of the room, then the distance between the boundaries and the listener will be different for each one. Listener position is as important as source position when considering what is heard.

Also, I think it is worth a second mention that damping is as important as position. The standing waves setup by reflections act as resonators. Damping serves to smooth the response, just like a properly loaded crossover keeps its response flat. If a crossover isn't loaded properly, it will develop a peak because the circuit resonates. The same thing is true of room modes. If the room is well damped, the room modes are reduced. Framed drywall construction tends to damp room modes because the walls flex and absorb bass energies. They can be augmented with bass traps or large flexible panels or membranes.

I'd suggest using multiple woofers, and if in a room with rigid walls (like concrete basements), add bass traps. Model the room with CARA to determine where to place the subwoofers, and bass traps, if needed. Decide what positions are available for subwoofer placement in the room, and use CARA to test what placements work best.

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