Legacy Audio Goliath XD - Manual (Page 8)

8
Speaker Placement
Now, while such reinforcement might actually be beneficial at very low
frequencies,
a way to minimize excitation of these resonances is to place
your subwoofer asymmetrically relative to room boundaries. For instance, if
the subwoofer is 2 ft from one corner wall, then place it 1.5 ft to 3 ft from
the other.
Placing the subwoofer in a corner will reduce the radiation angle and thus
increase efficiency. It will also excite the maximum number of room modes
and decrease distortion.
A best case scenario is to actually use two subwoofers, one to each side
of the listener. The subs should be placed 90° out of phase with each
other. This improves spaciousness and bass uniformity, with a reduction in
room level peaks.