There is no simple answer. It's not that black and white. Changes, small and large, have been made to the speakers over the years, and Axiom simply reached the point where they felt it would be appropriate to designate the current breed as V2s. Nothing more; nothing less.

Also, though I have no personal knowledge that it is the case, it's possible that Axiom wishes to keep the improvements private. It is their prerogative to do so.

Jack

"People generally quarrel because they cannot argue." - G. K. Chesterton