I'm using a pair of A11s for a system for a friend. First cab I built was a modified inverted BIB. All 4' lumber since my woodworking skills and tools are ridiculously limited, so just working within my limits. Got the usual 180 bend at the top then a pair of 90 bends at the bottom, the lowest going to the point and the higher one bending toward the mouth which is actually rear firing, and that gets me a line of around 102" (though all the folk who've built to design in the past, like gychang, have build 120" BiBs). Flat down to 50Hz and you can actually hear a solid 20Hz tone from them. Tried a slimmer, upfiring 4' BiB next which had no bass at all (think that enclosure volume was just too low), and then a basic BR cabinet built from some 8" sonotube and wooden end caps. The BR, when running manual tone sweeps was in fact getting more extension, but I think its ripple was even worse than the BiB. Couldn't hear any with the BiB, but with the BR, it was down earlier, then back up after the BiB was effectly rolled off, and then the 20Hz tone, while there and fairly loud was badly distorted. To make matters worse, the BR doesn't provide any gain through the LF, so it just sounded small and forward whereas the BiB was alot more balanced and sounded expansive. So, after much research and experimentation, I started work on the second large BiB cabinet for the A11 last night.
Kensai