This is from Rory, the product manager at parts express
"Very happy to oblige.
Hint: You really don't need a huge box for this driver, thanks to the middle-of-the-road Qts, but if you want solid response into the teens, that's one way to get it. Infinite baffle is another. Xmax is enormous, but there's even more Xmech available.
If you've only got room for a smaller box, the UM18-22 will also work well in 4 cubes, sealed, and with as much EQ as you care to throw at it. The 1000W RMS power rating is conservative for the coil."
And something like 15 pounds heavier than the 15" version.