The Sweet Sixteen discussion reminded me of a simplified folded horn design my dad built from some long lost plans in the late 50' or early 60's. They had a single 8 or 10 inch driver in a simple 3 chamber box. The speaker sat in the top of the middle chamber angled back firing upwards into a lid that that dispersed the sound. If any one has those plans, I would like to recapture the design.
The folded horn will work in the upper mid range or even mid range.
The horn would have to be 20 feet across to work for bass frequencies.
That's why the folded horn design has been all but abandoned, it don't work for Hi Fi.