Zd, I used this technique with both the 1.6s and the 3.7s. This technique does not roll off the high end, which would more likely occur by turning or tilting as you suggested. What this technique does is reduce the time smear from an individual driver to the extent possible, but it certainly does not reduce it to zero. The speakers sound better, but it does not really change the tonal balance to make them more or less bright or warm. If you think about how this plays out with, for example,the ribbon, when the panels are tilted to achieve a perpendicular from the mid point to ones ear, then the distance from the top of the ribbon to one's ear and the bottom of the ribbon to ones ear is equal. This would give the lowest total amount of smear. On the other hand, if the panels are tilted back, then the bottom of the ribbon may be 6 -8 inches closer to one's ear than the top, and each point from top to bottom is a different distance from one's ear. This arrangement gives the maximum time discrepancy possible. In practice, I found this improvement to be more significant with the 1.6s, but it also helped with the 3.7s.
Bombaywalla, I take it you are not a big fan of Maggies!
Obviously, I draw a different conclusion than you do, while conceding that the unique Magnepan design brings with it some unique compromises. Those you have heard may not sound right to you, but Magnepan has a lot of fans who are not tone deaf knuckleheads, who would express a much different conclusion. Magnepans can sound heavenly in the right room with the right ancillaries.
Sometimes, the problem is the recording. Some times, the problem is the room. Sometimes, it is the wrong speaker for the room, but would work well in another room. I have recounted several times in this forum a concert experience from the late 80s, listening to an Isaac Stern recital. If I had closed my eyes, I would have said this is the worst screeching ear-bleed inducing bad digital recording I have ever heard. It was a world class violinist, playing a superb instrument, but unfortunately, it was the wrong seat in the wrong hall for that violinist and violin. It sounded really really bad. I don't know that it had anything to do with time coherence. Later that year, I heard Itzhak Perlman from the same seat, and his playing was sweet as honey.
Likewise, any room not constructed as a perfect sphere or an anechoic chamber is going to reinforce and diminish certain frequencies. This has nothing to do with speaker design. Treating a room to reduce unnaturally reinforced frequencies makes sense to me.
As I said before, if there were a perfect no compromise design everyone would use it and life would be simple.
