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Making Sound with Plasma - Hill Plasmatronics Tweeter

Closeup of Plasma Tweeter

At the 2023 AXPONA show in Chicago, I had the opportunity to see and hear the Hill Plasmatronics tweeter. I also had the great pleasure of meeting Dr. Alan Hill, the physicist who invented this unique device.

Benchmark visits Dr. Hill at AXPONA 2023

Dr. Alan Hill (center), his son (left), John Siau (right), and Rory Rall (rear)

The plasma driver has no moving parts and no diaphragm. Sound is emitted directly from the thermal expansion and contraction of an electrically sustained plasma. The plasma is generated within a stream of helium gas. In the demonstration, there was a large helium tank on the floor with a sufficient supply for several hours of listening.

I had read about Dr. Alan's plasma tweeter and was thrilled to hear that he would be demonstrating it in public for the first time in forty years. With great excitement, Rory Rall and I headed to the Plasmatronics room at AXPONA 2023. As we approached the room, a faint smell of smoke filled the hallway. This intensified as we entered the room. We could now see what appeared to be two flames burning inside of protective cages at the front of the room. A few moments later we experienced the amazing sound produced by the strange collection of equipment.

Hill Plasmatronics Tweeter Demonstration - AXPONA 2023

This wonderful sound was interrupted when one of the presenters walked to the front of the room and blew out the plasma just as if it were a burning candle. Instantly, the frequencies above 1 kHz were gone and at that moment we realized just how much sound was coming from what looked like a burning candle inside of a bird cage. After adjusting the flow of helium and pressing an igniter button, the sound was restored!

While a tank of helium, tubing, high voltage power supplies, and the smell of smoke may not be appropriate for every living room, this was absolutely the best thing I experienced at the show.

Special thanks to Dr. Hill and the others who made this unique demonstration possible!

- John Siau

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