At last year’s AXPONA, turntable specialist Brian Walsh of TTsetup.com invited people to hear his restored Hill Plasmatronics loudspeakers. It was an unforgettable sonic experience that you can read about in Issue 218. I don’t use the word unforgettable lightly.
The Plasmatronics speakers utilize a plasma tweeter, which produces sound by varying the surrounding air pressure via an electrical plasma, as opposed to the conventional means of moving air via a physical driver diaphragm. The plasma heats the surrounding air, which causes it to expand. Since the plasma is electrically conductive, it can be modulated by an audio signal. The air expands in accordance with the signal applied to the plasma driver, which creates variations in air pressure, aka sound. But in order to create the ionized plasma, helium gas is required. The gas is stored in tanks. Most people would not have such a system in their house.
Brian Walsh is not most people.
So, when he called me before AXPONA 2026 and told me he had assembled a system that was even more extraordinary than the original, one based around the restored Plasmatronics tweeter and four Quad ESL 57 electrostatic loudspeakers, I knew I had to hear it. Brian is not one to spout hyperbole. And the transparency and “closest approach to the original sound” of the Quad ESL 57 is legendary. But because of my crazy-packed AXPONA schedule and the fact that he was off site, I could only spare about 45 minutes.
I only needed about 45 seconds.
The sound was astonishing.
Before I wax poetic about it, some tech: The Quad speakers are stacked two per side, with the bottom speaker oriented upside down from the top one. The Plasmatronics tweeter is mounted in the middle. All are housed in a custom adjustable metal frame designed by Brian. The analog source consisted of a Dohmann Audio Helix One Mk3 turntable with Supatrac Blackbird arm and Symphonic Line RG8 Gold cartridge, going through an Atma-Sphere MP-1 preamp.
The Quads are driven in series by Atma-Sphere MA-1 OTL (output transformerless) amps, while the Plasmatronics tweeters are supplied with their own high-power MOSFET amps designed by Tony Salsich. The low frequencies are handled by a pair of Fried “coffin” transmission line subwoofers with KEF B139 bass drivers. The subs are driven by PS Audio BHK 300 mono amps.
The front and back of the Plasmatronics tweeter. Courtesy of Frank Doris and Brian Walsh.
What made Brian decide to create this system, aside from a drive for reaching the sonic stratosphere? I’ll let him tell the tale:
“About three years ago I heard about a pair of original Hill Plasmatronics speakers that someone wanted to sell. Having heard such speakers back in the day, I wanted them – if I could be sure they would work. Considering that I knew Tony Salsich, who had worked for Plasmatronics designer Alan Hill for quite a while and lived in northeast Wisconsin near me, I figured he could be available for a bit of technical assistance. I bought the speakers, and several months later I had replaced the old woofer surrounds and the capacitors in the passive crossovers. With Tony's help I got the speakers running.
Although I had spent time and money to replace all of the capacitors in the plasma module electronics and the interface/crossover unit, I thought I could do better, by getting away from the speakers’ cone midrange drivers and woofers, which didn't integrate as well as hoped with the tweeters. There was some noise and hum as well.
Tony had shown a prototype Plasmatronics tweeter system at AXPONA 2023, using solid-state electronics and a pair of Eminent Technology speakers, which were a better match with the tweeters better. Alan Hill was there and was delighted.
Some time later, Tony mentioned that a record mastering engineer had purchased that kind of tweeter system from him, sitting on top of a pair of Quad ESL 63s, which I found intriguing. That pair of tweeters utilized [some] old drivers from original Plasmatronics speakers, since these drivers were not available any other way.
Last fall, Tony said he was hoping to make new drivers, for the sake of making and offering complete tweeter systems based upon his newer approach. That started me thinking.
Brian Walsh and Tony Salsich. Courtesy of Brian Walsh.
I remembered the old Mark Levinson HQD system from long ago, using stacked Quad 57s in custom stands with Decca ribbon tweeters between them. Combined with the fact that I had three pairs of old Quad 57s, which had been lying around for a long time in various conditions, I threw down the gauntlet and called Tony to say I wanted his new tweeter system.
I sent Tony some money to get started once he determined it could be done. Months later and after a lot of work, the system came together this year, just in the nick of time to demo to people in my home about 20 minutes away from AXPONA.
Kent McCollum of Electrostatic Solutions in Kansas City, Missouri restored my speakers, and I designed custom stands for the Quads and had them fabricated locally.
Local audio dealer Joe Galanti of Superior Audio in Chicago very kindly loaned me his big Fried ‘coffin’ transmission line subwoofers to use for the demos, since a pair like them would have taken some time to build. A friend who owned a complete HQD system back in the day had reported that Fried coffin subs and Quad 57s match very well together. Long story short, he was right.
For lack of a descriptive name, I call my system the HQK, for Hill/Quad/KEF. It's a reminder of the HQD name.”
For the demo the system utilized a DSP unit (from miniDSP) as an adjustable crossover to determine crossover points, slopes, delays, and levels. The Plasmatronics tweeters cover the frequency range from 1,000 Hz to 100 kHz. The Quads operate between 90 Hz to 1,000 Hz. The subwoofers cover 90 Hz and below, down to approximately 10 Hz. The crossover slopes are 24 dB/octave and no time delay is necessary. It will eventually be upgraded to a Marchand XM-126 3-way fully-balanced active tube crossover.
As Brian noted, “It was a roll of the dice. It works extremely well.”
I’ll say. You and I have heard terms like “transparency,” “lifelike,” and “musical realism” to the point where our eyes glaze over when encountering such descriptions. I certainly am guilty of overusing them. But this HQK system takes these attributes to a remarkable level. The psychological dividing line between “I’m hearing a stereo” and “this sounds real” is, I won’t say obliterated, but the illusion of feeling like you’re hearing reality instead of reproduced sound is uncannily strong. If you like hearing female vocals – and who doesn’t? you’ll find them captivating. A jazz recording (sorry, I didn’t note the name of it) really did sound like a time machine taking you back to the original event. Even with my compromised high-frequency hearing, the spooky action of the Plasmatronics tweeter was unmistakable.
Need I bother with a laundry list of audiophile attributes like soundstage, depth, resolution, imaging and on and on? No. I’ll just say that this was one of the best audio systems I’ve ever heard in its ability to reveal the sonic truth of a recording, convey a sense of space and time, cover the full frequency range and beyond, and most of all: convey the emotion and artistry of the music with little if anything between the performers and the listener. The plasma tweeter and the electrostatic Quads are a sublime match. In audio as in life, if you set your mind to it, the possibilities are endless.
The HQK system is a monument (almost literally, considering its size) to Brian and his team’s no-holds-barred dedication to the pursuit of the ultimate. Special, magnificent, and a once in a lifetime experience. Until next year, Brian?
Kent McCollum, Quad enthusiast extraordinaire Robin Wyatt of Robyatt Audio, and Tony Salsich were very happy with what they heard. Courtesy of Brian Walsh.
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If you’re seriously interested, you can contact Brian to schedule a visit to hear the system.
The introductory price of the Hill/Plasmatronics Type 1B tweeter system is $25,000.
If desired, new Quad ESL 57s can be purchased from Electrostatic Solutions for about $8,000 a pair.
Custom stands can be made for about $2,000.
Contact Information:
Hill/Plasmatronics LLC
Appleton, WI
Tony Salsich
hillplasmatronics.com
info@hillplasmatronics.com
Quad ESL 57s restored by:
Electrostatic Solutions
Kansas City, MO
Kent McCollum
estatsolution.com
esolution@estatsolution.com
913-208-7657
Brian Walsh: system owner and designer
brian@ttsetup.com
773-809-4434
Header image courtesy of Brian Walsh.
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