Well, he only ever made the one reference speaker, albeit with a couple generations of improvements. There was never any trickle down into his “normal” speakers. Either he was unsatisfied with his huge horn but didn’t know how to take it further or he couldn’t bring out a version for mere mortals and it was a dead end one off statement piece.
I heard his horn twice in Munich and there was some real potential even though I felt using Pass Labs SS amps to drive it was not the best choice and held back that potential. It easily surpassed any of his conventional speakers I have heard…I haven’t heard M9 but it looks like more of the same just bigger.
Ironically, I found one of his earlier large speakers in wood cabinets (M1 or M3 maybe?) to be more enjoyable than the later metal cabinet speakers.