On a gig the other night, I was troubled by the occasional high pitch feedback type squeal. Managed to get through okay. Just testing at home to investigate the problem, and it's weird. It seems to happen when I get close to the amp (as you might expect with feedback), and some basses seem slightly worse than others in this respect. The highs from the amp are way attenuated, which leads me to suspect the tweeter is shot. But he squeal is still there, and I think it's coming from the tweeter. I've eliminated the leads and the bass as the problem as it still happens when I switch these for something else and it doesn't happen with my other rig. So, questions: 1) Why should it start squealing when it hasn't done so before with the same rig (and even in the same venue)? Is squealing a symptom of dead or dying piezo tweeters? 2) Do you think the squealing was CAUSED BY a problem with the piezo tweeter? Or could the squeal initially have been due to something else and the tweeter then got blown because of excess HF energy? Opinions welcome, especially from piezo experts.