Just got my setup last weekend and finally got around to setting them up. Got two M60's, VP150, and 2 QS8's. Did the test tone and noticed one of the M60's sounds different. One matched the VP150 perfectly and the other, well it sounded like it was muffled and not hitting higher frequencies. I switched the wiring around so it was using the same speaker terminal as the good one. No change and the other M60 sounded fine on the bad ones terminal.

So bad speaker?