Hi Tom,
No doubt that the drivers aren't the same at all; Mark has mentioned at least once or twice that practically none of the T/S parameters are the same as the stock LAB15 driver. At the same time, it's still a member of the family so to speak, sharing the same cone, surround, basket, etc. While it's fair to assume Mark has highly optimized the driver to his purposes, I don't think it's realistic to expect 30+mm of linear stroke (which you'd need to deliver significantly more clean output than the XS30se from 20Hz-63Hz). It's also worth pointing out that Mark himself has always stated that the drivers he's using are relatively modest as compared with visually impressive long throw units like the SVS Ultra 13 driver. Instead, the idea (as I'm sure you're familiar with) was to make good with massive amounts of Sd from a pair of inexpensive, albeit effective medium stroke units, and make use of a relatively high system sensitivity above 40Hz or so.
Of course I'll be happy to see both units get tested by Josh. There have been a lot of interesting claims made over the years, and it'll be nice to replace hyperbole and conjecture with facts. The question "how does the SubM compare to X" comes up every so often, and it's hard to give much of an answer as is.
