As far as my experience goes and from what I know of audio engineering piezo-electric elements are terrible at flat frequency response and mostly unusable excep

As far as my experience goes and from what I know of audio engineering piezo-electric elements are terrible at flat frequency response and mostly unusable except as beep generators. There are (older?) models of Behringer cheapo PA-speakers with piezos as high-frequency drivers and they are beyond terrible. Didn't deep read the article however found no hard info as to if some kind of breakthrough has been made.