actually. at any particular frequency over say 15k, the combing would, I think, manifsted itself as a ripple in amplitude as you change vertical position. The ear would average this to an rms value (maybe), hence you get the apparent lowering in spl at high frequencies. Sorta makes sense, perhaps. That means that it could be counteracted by using tweeters with a rising response above say 15k.Disclaimer, all this is pure conjecture. ;-))