I second Rwwear's suggestion of experimenting with various toe-in angles, and I suggest that you do that as thoroughly as possible, trying many angles. Here's my reasoning:
Bob made an excellent find with the S&V frequency response plots. Here is a direct link, which provides additional information:
http://www.soundandvisionmag.com/speakers/2271/test-bench-b-w-cm-series-home-theater-speaker-system.html
As you'll see there, the plot reflects an average over a +/-30 degree listening angle, with double-weight given to 30 degrees (presumably corresponding to a typical listening angle with the speakers aimed straight ahead). The corresponding plot (the green line in the figure) is basically a roller-coaster in the upper mid-range, swinging nearly 10db peak-to-peak.
As Atmasphere (Ralph K.) has pointed out in other threads here, it is common for certain amplifier distortion products to create the subjective perception of brightness. My suspicion is that the reason for the different behavior with the two amplifiers is that with the Rotel the predominant distortion products happen to fall at the peaks of the roller-coaster with the music you tend to listen to, while with the NAD they are happening to fall into the trough.
But regardless of whether that theory is true, it seems to me that the roller-coaster frequency response curve, that occurs right in the problem area you are describing, is likely to be the root cause of the problem. And hopefully it can be improved by simply re-aiming the speakers. Many of the other suggestions that have been offered may subsequently help further, but without first addressing that frequency response roller-coaster they strike me as using a band-aid when a tourniquet is required.
Regards,
-- Al
Bob made an excellent find with the S&V frequency response plots. Here is a direct link, which provides additional information:
http://www.soundandvisionmag.com/speakers/2271/test-bench-b-w-cm-series-home-theater-speaker-system.html
As you'll see there, the plot reflects an average over a +/-30 degree listening angle, with double-weight given to 30 degrees (presumably corresponding to a typical listening angle with the speakers aimed straight ahead). The corresponding plot (the green line in the figure) is basically a roller-coaster in the upper mid-range, swinging nearly 10db peak-to-peak.
As Atmasphere (Ralph K.) has pointed out in other threads here, it is common for certain amplifier distortion products to create the subjective perception of brightness. My suspicion is that the reason for the different behavior with the two amplifiers is that with the Rotel the predominant distortion products happen to fall at the peaks of the roller-coaster with the music you tend to listen to, while with the NAD they are happening to fall into the trough.
But regardless of whether that theory is true, it seems to me that the roller-coaster frequency response curve, that occurs right in the problem area you are describing, is likely to be the root cause of the problem. And hopefully it can be improved by simply re-aiming the speakers. Many of the other suggestions that have been offered may subsequently help further, but without first addressing that frequency response roller-coaster they strike me as using a band-aid when a tourniquet is required.
Regards,
-- Al