Enjoyed this pair for several years. Best speakers I've ever had. One began chattering. Sent electronics to LM for evaluation. They declared it OK, so had to be a problem with the membrane. The other speaker seems fine. Since the malfunctioning one got direct afternoon sunshine from the back and the other was in the shade, I'm guessing UV damaged the membrane. Can't confirm this without sending the whole thing back. I elected instead, since both are old, to replace both with ElectroMotions and be done with it. I love ML electrostatics but would suggest a stronger warning in the manual about exposure to direct sunlight, just in case. Thanks for your attention.