Nearby walls boost loudspeaker bass output, and designers counter this in many ways.

Evidence

The effect of the presence of boundaries, such as walls, on the low-frequency output of loudspeakers is well known (Allison, 1980). Many methods of ameliorating these effects have been proposed, ranging from careful positioning to special speaker designs that try to remove the effect of the boundaries. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2132

Categorization

• XREF: Allison (1980) is the classic reference on boundary effects; useful lineage pointer for psychoacoustics history.