An Eminence Magnum 18HO will work in that enclosure. You can purchase them new for about the same price as a used JBL 2241. It has a shorting ring like the JBLs, so it's a nice driver.Like the 2241, it would be flatter if the cabinet were tuned a little differently, but as it is - 10ft3 at 42Hz, it will have about the same response curve as the 2241 in that box. Flat down to 40Hz or so with a slight 2dB rise at 50Hz. I'd say this is a pretty good choice.