High qts - large xmax drivers

Could anyone please recommend a 15", 18" or 21" driver with a high qts (0.7 or higher), a large xmax (24mm or higher) and a low Fs?

Try looking at in-car subs. If you can't find one big enough, you can always use more than one (and wire them in series to get a sensible nominal impedance).

maybe take a look at the bms 18 n860 18" driver. its got a 19mm xmax, but qts is a lot lower than 0.7. you could try weighting the cone by replacing the dust dome with a machined piece of aluminium with a bolt in thecenter. you could then screw different weights to the boltto increase the mms and make it perform more like the type of driver you are looking for(kinda like how you tune a passive radiator). though, it has a relativelyheavy moving mass to start with. another option is the ciare 18.00sw. one of the only pro drivers to have a spec similar to what you are looking for. What you are asking for is a rubber edged woofer made by someone like aurasound.

JS wrote: Could anyone please recommend a 15", 18" or 21" driver with a high qts (0.7 or higher), a large xmax (24mm or higher) and a low Fs?

though discontinued, the Cerwin Vega 18 inch D2 is looking like an awsome driver for your needs. qts of just over 0.6 and an xmax of 19mm. 300ltr reflex is showing an f3 of 24.5hz.

thedriver is 96db/1w/1m, which is good for a driver with this type of xmax.

Thanks for the info, i'm trying to find a driver for open baffle use. Only one I can find especially made for this is web.archive.org/web/20040307231755/lambd...rivers/DIPOLE15.html
$279 each + shipping + tax is a bit pricey though.

If your setup is going to look like what I think it will, I strongly suggest having a look at Lynn Olson's 'Beyond the Ariel' thread over at diyaudio. He is using an open baffle + compression driver concept, and if you know about his previous design, the Ariel, you'll know the detail the thread goes into...

Lambda acoustics is defunct. They used to make the diy Unity horn, you know.