@pdreher your post intrigued me as the standard SLH5s are said to be a tad less open than the plus versions. But then again sensitivity to brightness and sibilance does seems to vary from listener to listener.
I find that in my case it definitely increases if the overall sound fails to captivate. As soon as the music fails to hold my interest I find myself almost immediately beginning to notice sonic flaws which I was previously hadn't noticed.
The fact of the matter is that it's very rare to find any dome tweeter that remains impeccably clean. I've yet to hear one. Of course implementation and crossover points are vital as we know tweeters begun to break up towards the low end of their operating range.
Sometimes designers will take a tweeter low in order to match it's room dispersion characteristics to that of the woofer. Problem is that this will take you somewhere deeper into the vocal range.
The cleanest and most delightful treble I've heard were the ribbons used on the Kerr Acoustic K320s. I couldn't tell if they were blemish free, that would have needed some sibilance torture tracks played loudly, but I couldn't hear anything obviously wrong.
It would be interesting to see how good ribbons compare with some hi-tech designs such as the B&W diamond domes or even some beryllium designs as used by Focal because to my ears treble can never be clean enough.
