Never heard of this technology before, it's pretty Sci-Fi: The Lansche "Corona Plasma Tweeter" has no physical diaphragm at all. Instead, a high-voltage arc is established between a small circular electrode within the tweeter's combustion chamber and another circular electrode outside the chamber. In a process called corona discharge, the arc ionizes the air within the chamber, forming a gas called a plasma (as seen in the photo at the top of this blog), which responds to the musical signal modulating the arc current. This causes nearby air molecules to vibrate in response, much like lightning causes thunder. The tweeter has virtually zero mass and can easily reproduce extremely high frequencies with no resonances, break-up modes, or other bugaboos that can plague conventional tweeters. Unfortunately the cheapest Lansche speakers it's found in cost $25,000 but they can apparently produce up to 150kHz!