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Audax HT210K. Looks to be about a 25 or 30 year old driver, but it has some very interesting TS parameters. I have looked at it several times over the last year or so and finally decided to model it. It models very well for a driver with FS over 60Hz. It has parameters similar to the better small form factor woofers our there - a high-ish Qts and a relatively low compliance. This combination yields a surprisingly good result in vented enclosures.
I modeled using 4.5mm estimated Xmax, that is right around where so many of those older woofer designs seemed to be. For all I know it is 1.5mm and I am way out of whack here, but this is an intellectual exercise so who cares, right? Maybe one of us will buy one and take it apart to measure the coil and gap and see whats up.
Anywho, in line with the vented modeling for high-ish Qts and relatively low compliance, it digs reasonably deep for a given cabinet size with excellent excursion control. Not an SPL monster, at the modeled 20 watts you can expect 102 db before baffle step losses but for most of us (definitely myself included) a speaker capable of hitting 95+db at 45hz will be fairly adequate in the majority of listening sessions. That is louder than we peak at DIY events, for example.
Check it out:
You can find it here:
Maybe ol' Steve can do a group buy on a bunch of these and those cool looking Cerwin-Vega wave guide loaded tweeters. That might make a fun challenge for IowaDIY!