I've been looking for a "bug" in my system...a kind of resonance sound - like something loose and vibrating in the speakers themselves - a "fuzz". I removed the tweeters which were sent back from the manufacturer as being fine...removed the mids - same story....removed the crossover - same story. I noticed that the sound gets worse after a couple of minutes of playing....so - out went my 130 lb. amp. The manufacturer says everything specs out ok, but would recommend changing the caps (2) - fine .....we'll take a listen upon its return. I've been chasing this thing for over a year.