Here's an idea I've been developing for the 2152H coaxial drivers I have littering my basement. It's a rear-loaded dual corner horn with a very small footprint (1 sq. ft.) The expansion is conic to keep the carpentry simple. The cabinet would run floor-to-ceiling for 1/8th-space loading of both horn mouths. A Hornresp simulation shows very high efficiency down to ~60Hz.
Any thoughts?
Bill