I hadn't seen this before, and I didn't recall any discussion of it here:

Audyssey BassXT

The way it's described makes it sound similar to Axiom's XLF, which of course makes me doubt it would have much effect on Axiom's DSP-controlled subs. Of course, they apparently have to work with each sub manufacturer if they want their products utilizing the feature. You have to wonder how much time they put into each model, and how their results would compare to Axiom's digital code. Not that I've seen any BassXT-enabled products.
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SuperGrand UltraDeluxe (Plus Extra More)