Maybe during that test the binding straps were a little loose? That would give lowered high frequencies. One bad driver?

During Mojo and I's testing of the M60,M22 and M80, the M22s were the most bright followed by the M80 and then M60. When we had Robb's M3s, we found them to be more like the M60s, still less bright/forward than the M80's and even lesser than the M22's.

I am still thinking that the AB's are probably like the M22's and M2's(I have never listened to these yet) and should sound more forward/bright than the M80s.

Since you stated the M3's/M50s being brighter than the M80s, which most around here don't agree with, certainly sounds like you might have something wrong.....er, with the speakers or receiver that is.

Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70