Clearly, it has to be the Plasmatronics, which hasn't been made for years now.
This monster used helium gas and converted it to plasma, the fourth state of matter. Then, this purpleish glowing spherical ball of plasma was modulated by a direct drive tube amp, which had a 5000 volt plate supply, if I remember right. The surface area of the plasma sphere became the point source radiator and let me tell you, from 700 Hz up, it was flat out perfect. It also used a very large tank of helium each year, too.
It didn't work below 700 Hz so you had to complement it with subwoofers and stuff. The problem is, nothing would mate with it well, so there was always perfect sound mixed with non perfect bass. It was huge, too; reminded me of a loveseat put on its side and you had two of these things in your living room. It was one helluva system, let me tell ya. That purple ball of plasma floating in space really caught your eye.
The other speaker system I heard that had a lot of promise, but wasn't finished, was a spherical point source electrostatic. Richard Shahanian and another engineer perfected a way to make a spherical electrostatic and that had a lot of promise. Unfortunately, Richard doesn't own the patent, otherwise I am sure he would have perfected it.
Of course, Shahanian's Diapazions are very good, which is why I saved for years to buy them.
