Klipsch KPT-1802-HLS Mode D'emploi page 4

PLACEMENT
The KPT-1802-HLS is designed for behind-the-screen placement on the
floor and against the back wall for quarter-space loading producing
3dB additional output vs. half space (no boundary other than the floor).
For larger theaters dual subs positioned next to each other, wired in
parallel, gain an additional 6dB in efficiency due to mutual coupling.
SINGLE SUBWOOFER QUARTER SPACE FLOOR/WALL PLACEMENT
All manuals and user guides at all-guides.com
Additional mutual coupling occurs for up to 4 subwoofers placed next
to each other. An asymmetrical configuration of multiple subwoofers
minimizes standing wave stimulation for more even bass throughout
the theater.