[Jerome W]

I agree with Shane.

For both my Gat and my Premier 17LS, when the speakers are phase inverted, I can hear the difference easily. But I must be at the sweet spot.
Elsewhere in the room this is not always obvious.
I had the system playing with inverted phase when E. came to visit and since I was not at the sweet spot I did not realize it.
But putting back the speakers on phase with the CJ preamp ( + connection with - of the cable ) made a huge difference even not being at the sweet spot.