I had been using a "lesser brand" speaker for center for a while until I got an M3 to match the other M3s across the front, and one of the things that got me to go with the M3 was the sibilance I'd experienced with the lesser speaker-it absolutely sounded like fingernails on a blackboard!(ok, it's an exageration! but it was annoying!)

(The test case was the donkey in Shrek; makin' wafflesssss)

The M3s don't have it, and I don't miss it! Regardless of Where it comes from-sibilance is yucky!