Distortion is obviously directly related to excursion. With a quick look, the only one that i could find that had distortion figures was the Adire Maelstrom, advertised as 3% THD, 16 Hz - 200 Hz, @ 105 dB SPL in a sealed box.

The drivers I mentioned range in sensitivity from around 86db/1w/1m to 94db/1m/1m. They are less sensitive then many JBL drivers and whatnot, but that's the trade off for the long excursion. The Adire Brahmas have been DUMAX'd at 27.32mm one way. Dumax measures excursion by cone travel before BL drops below 70% I believe it is. So a lot of these drivers are touting excursion levels two to three times that of the best JBL drivers.

There is indeed no free lunch... Most of these woofers will need more power and don't have the useable bandwidth of say, a JBL pro woofer, or whatever. However, that is not to say they don't maintain reasonable sensitivity ratings, and the bandwidth issue is just something you have to deal with. Pro woofers and car/home woofers are designed for different frequency response applications (wide bandwidth use vs narrow bandwidth) so this isn't an issue.

I'd never recommend a woofer like this for a 2-way system even if it had the bandwidth. The intermodulation distortion of a woofer throwing 15mm xmax delivering 30 Hz notes while also trying to throw out 1,000 Hz notes would be just unbearable.

When it comes to any situation where you are using the sub only up to 80 Hz or so and have plenty of power on tap, I feel choices like these are superior.

Adam