I've never heard one.
Now that I've listened my M80s for a while I know its time to start. I've heard some amazing recordings and some that I'd delete/through out if I had better copies.
Best $1500 I ever spent.
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3 M80HP
2 QS8
2 QS4
RX-A1010
ADA 1000-4
PT-AE8000
PS4
Seymour XD
7'x 12'x 21' cave
3 Paradigm subs