I got to thinkin' about the question of QS4s and QS8s in the same 7.1 system; and a couple of "what ifs'" came to mind.
(Mostly thinking of the great majority of 5.1 mixes here)
Since the rear surrounds in a 7.1 are mounted on the rear wall and sometimes the listening seats are required to be very near(or touching)said rear wall, perhaps a smaller set of speakers mounted there could be an advantage.
Another thought: If there is a slight difference in sound between the 4s and 8s, would that help in adding an increased feeling of spaciousness by separating the effects(such as boids choippin' and crickets chirpin' which may have a slightly different sonic signature thru each different speaker type)and keep these individual sounds from filling such a large quadrant all at once? They would still be diffused, but more, perhaps, "over there, somewhere" than all around back thisaway.
understanding that there would be crossover questions, and probably a few other hurdles, but,...what if?...
