I read MJKs very helpful paper from http://www.quarter-wave.com/OBs/U_and_H_Frames.pdf This shows for a single
woofer amongst those three options, the H Frame has (slightly) the lowest f3 and the most output around 250 Hz. In exchange for the lowest efficiency. With an H frame, if the 'wings' were on all four sides, rather than just two opposite sides, would it probably make only...