The Piezo tweeter is a strange beast. I hated it firing up at an angle on the Pi variation I built, I thought the treble was outstanding in Wayne's room at MAF, and others have found it "hot" or just right. Go figure. There are alternatives but most are inefficient and have colorations of their own. A very good alternative is what "Godzilla" posted on the single driver forum for a Radio Shack version of the KSN. He removed the "cone" from the basket and coated it with varnish, damped the basket with Mortite and put a ressitor in series. Some or all of that may work for you. Creating is more like performing than listening