U-frame with 18" PA driver

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This driver

http://hcdesignaudio.com/hcdesign/assets/File/IT 18S.pdf

is on sale here right now. Beautiful motor, supposedly very linear spider, +/- 9.1 mm linear travel. The big bummer is the highish fs of 49 Hz together with the rigid suspesion (Vas = 89 l).

For use at a home sub, I would like to get signicant efficiency in the 20 - 50 Hz range. However, this driver seems to do only one thing well, and that is a 200 - 300 l ported box with an fb of 37 to 40 Hz.

I tried sealed, ported and detuned ported (EQSS), and always the XXLS12 came out more efficient in a similar sized enclosure.

So the last hope to find a good application for this driver is a dipole, preferably a U-frame. However, a U-frame would also result in an fs of roughly 45 Hz. A H or W-dipole might get 40 Hz, but I am not happy with the radiation pattern.

Is there any sense in building a U-frame with a driver fs that high? I suppose only if supported by a conventional sub in the < 40 Hz range, correct?


I also suppose the only way to make the spider softer is to drill holes into it, which may have unexpted side effects.
 
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