Moving a subwoofer away from a boundary toward a null reduces modal energy room-wide.

Evidence

Here we are modifying one of the modal coupling factors, ΨS in the Equation 14.2 numerator. Moving the sound source away from a room boundary closer to a null reduces the energy transfer to that mode (Figure 14.6). This is almost the same as is discussed in the previous section, with the difference that the attenuation of the room mode is experienced everywhere in the room. — Toole, Floyd E, Sound reproduction- the acoustics and…, 1577