Well,
knowing the original poster personally I imagine the thread was going to drift to the fact that he is thinking of buying a speaker that goes down to 20hz. That is all well and good, but these tangents do tend to become more interesting when they drift.
First time I heard open baffle bass was in RMAF in 2007, Nelson Pass had built these OB subs in plywood, just hanging in the wind, and they sounded great...fast, clean,effortless, no box boom like a home theatre sub, much more musical, such deftness, like a real acoustic bass, like the bass came out of the f holes in the double bass, very very musical.
I remeber the first time I heard the IRS system at Bill Legalls house, completely rebuilt by him, I walked into this big room and saw these monster speakers surrounded by huge woofer panels, when he turned it on I thought I would be pushed against the back walls, all those woofers so imposing!!, But what I felt was the opposite, such a huge open delicate sound, so effortless, not like a nightclub at all, but like live music.
Rich is right you need big woofers and lots of them makes it better, but not how you would expect , not like a row of Marshall stacks, but they deliver such delicateness that is truly special. Extreme clean , fresh extended bass, super fast and lively, and so very natural sounding.
just my opinion all colored up and sticky
mike