U-frame woofer design

[john k...]

(JPK) I read some comments in another thread about resonances in U-frame woofers so I have presented a series of measurements outlining how the U-frame is actually designed and just what you get out of it. The 1/4 and higher resonances which occur in a U-frame are also present in H frames and W frames, etc. The resonant frequencies are dependent on the length of the U or H, W.... so they may occur at different frequencies. In shorter H and W frames they may be higher in frequency and may be ignored altogether in some designs, relying on the crossover filter to attenuation their level. The resonances can be pushed higher in U's as well, but the damping is an integral part of the design and is still necessary. The length of all these "frame" woofers is always a trade off between where the resonances are, physical size and SPL capability.

http://www.musicanddesign.com/NaO-II-U-frame.html