I have a Bryston (driving a pair of 2.3's) that developed a bad muting switch so that, when powering down, it bled juice into the speakers to the tune of a lot of horrific crackeling. Easily fixed, but very alarming. Sounds a bit like something similar (as noted above). One thing to be careful of, though, is that those coaxial drivers on the Thiels are a bit fragile. Don't know whether it was the Bryston issue or something else, but I managed to damage one of mine and ended up having to replace it. Play safe.
