Posted on July 22, 2015 by emmaco
The Flame Still Burns
“Then the music started and I was again startled by the clearest, most life-like reproduction of recorded music I’d ever heard. The recording being demoed was a solo A Capella contra-basso male voice. The image produced could have fooled me into believing the invisible man was singing in the room. When they functioned, they played better than anything I’ve ever heard.” Steven Kastner
“We suspect, though, that most audiophiles will find these speakers to provide the most mind-blowing listening experience they have ever known.” J. Gordon Holt, Stereophile
“The Single Best System Commercially Available.” J. Peter Moncrieff, International Audio Review
Ever seen these types of comments regarding a speaker before? You haven’t, because this speaker is truly unique. Here’s a few more from respected reviewers…
“We just stood there, dumbfounded, with our jaw hanging open.”
“So much closer to live music than anything else.”
“Our standards for being able to tell live from reproduced music have been forever changed.”
Imagine a speaker with no moving parts. No mass, no cones, no ribbons, no diaphragms, no enclosure, no Doppler shift, no resonances- just the ability to modulate the air directly.
Now imagine a perfect audio point source (the ideal pulsating sphere) radiating uniformly with constant phase. This has been the dream of physicists for at least a century.
There has been only one speaker that has ever come even remotely close to those lofty goals- the Hill Plasmatronics 1A, built in New Mexico by one of the world’s preeminent laser physicists.
Chances are you’ve never heard a Plasmatronics speaker. Not surprising, as only 52 pairs (we’re aware of Serial Number 70 though) were made thirty plus years ago. You had to be a dedicated hi-fi enthusiast to have heard them even back then.
The Hill Plasmatronics 1A was expensive- no doubt you could purchase a home in some parts of the country for the same price. It was complicated- vacuum tubes, helium tanks, an electronic crossover, multi-amplification, and even a rock inside each speaker.
Yet it was remarkably simple to explain its key virtue- if you played back a recording of a telephone ringing, someone in the house would come in the room and pick up the telephone. The Plasmatronics 1A did not require an extended listening session to prove its inherent superiority.
Lynn Olson once compared Alan Hill’s speaker as an SR-71 Blackbird lurking in a world of Boeing 737’s, a claim many owners would agree with wholeheartedly.
This site is dedicated to the enjoyment and preservation of this technological masterpiece.
Experienced audio insiders will stare at the two graphs above in bewilderment. This measurement (made by member JP) details the plasma units phase and frequency responses from 1 kHz to 20 kHz.
Suffice to say this is likely the best speaker measurement you will see during your lifetime. The linearity of both is staggeringly impressive.
Emotionally the Plasamatronic 1A is an interesting experience. After such an initial build up, one’s first reaction is it sounds just like any other speaker other than the sound is coming from a flame.
Ten minutes in you “get over” the technology and start to seriously listen to the speaker. The experience is someone detractive in the sense that nothing sounds wrong. There is no exaggeration of anything, nor nothing lacking.
Twenty minutes in you start to understand what makes this speaker so special. Every instrument sounds just right. We’ve become so used to the flaws in other speakers we tend to listen around them and ultimately make excuses for them.
No crossover points in the middle of the speech articulation bandwidth. No constrained volume. No thin bass. No phase discontinuities in the high end.
You just sit there in a stunned rapture, realizing you’re one giant step closer to audio nirvana, with a high frequency response that exceeds both your ears and the majority of audio instrumentation. The Hills are an ideal way to evaluate higher resolution digital audio tracks with greater than CD resolution (16 bit, 44.1 kHz sampling). We have listened to a variety ranging up to 24 bit/192 k resolution and they sound stunning.
I’ve never driven a well sorted Ferrari at speed on the Autostrada, nor drank a thousand dollar glass of champagne. But I have had the love of a beautiful woman and listened to the Hill Plasmatronics 1A. That’s more than enough.
Contrary to popular belief, Alan never worked for Los Alamos. He was working at the Air Force Weapons Laboratory at Kirtland Air Force Base in Albuquerque (presumably part of the current Directed Energy Directorate) when he formed Plasmatronics.
He was working on his PhD at UM Ann Arbor and working at Lear Sigler on a CO2 laser to be used for piercing of all things baby bottle nipples. He discovered the reason that CO2 lasers of that day could not put out much meaningful power, when the govt seized his notes and classified them.
His adviser, Peter Franken, told him to go to work for the government as it would be the only way to continue his work.
Nearly all the journalistic criticism of the speakers involve the low end of the speaker, much of it incorrect.
Below a switch selectable 700 Hz or 1 kHz crossover point, the Plasmatronics 1A used a conventional 14.1″ French built Son-Audax woofer and a 6.5″ midbass driver in two separate sealed enclosures.
The midbass enclosure included a medium size rock to break up potential standing waves within the small space. Rumor has it that these rocks were hand selected by Dr. Hill from the New Mexico desert.
The user had the option of using the internal passive crossover between the bass and midbass driver or using an external crossover and triamplifying the system via a rear panel connector. The passive crossover was housed within the low frequency enclosure.
Nominally this would require a 200 watt per channel stereo amplifier at a minimum to augment the system. Triamplification required an additional electronic stereo crossover and an additional stereo amplifier for the mid bass.
(Per member Tonehack) “Alan did build a lower range driver in the 80’s. It was downward firing because the helium had to be kept near all the little nozzles.
His eldest son, Larry, helped build it (he was home from college for the summer). It was a round, approximately 5″ diameter array of hypodermic needles embedded in the same blue epoxy that holds the commercial driver.
This array sat inside a kind of bell. Helium was fed through the needles and they were all electrically driven just like the commercial electrodes are. The sound output was measured with a microphone below the bell. I cannot remember the low-end cutoff, but it must have been around 200Hz.
The power required to make sound doubles for every octave lower i.e., the current driver uses many hundreds of watts to get to about 700Hz and 175Hz would require four times that power. It also needs a lot more Helium. This is one of the reasons why Alan did not really push this further. He was always keen to find a way to do it all without Helium. He even tried Hydrogen once, and did get a farily decent response, but the Hydrogen makes water and that made a lot of noise as it attacked the cathodes in the discharge. It didn’t work well.”
Other attempts to enhance the plasma tweeter have been made as well. One member has mated his Plasmatronics equipment to an Apogee ribbon based low end, augmented with a pair of Eminent Technology TRW-17 subwoofer systems, which may be the ultimate in high fidelity technology when integrated. The combined bandwidth of the components alone should exceed that of every other speaker system ever built.
P.S. Is that a lava light in the middle of the picture?
Plasmatronics listening is a little more complicated than with conventional speakers.
First and foremost, we recommend wearing polarized sunglasses while listening to protect your eyes. However beguiling, try not to stare at the plasma cells while they are operating.
Second, you’ll need to make sure the two internal helium tanks are filled up. If you haven’t filled yours in a few years, each tank runs around $200 each for industrial grade helium (with a tank exchange) here in Southern California in March 2015. I haven’t tried balloon grade helium which is substantially less expensive. Helium prices have risen 5x in the last fifteen years.
You’ll have to adjust the gas flow and current bias meters after startup.
Recently we bypassed the internal passive crossover and decided upon triamplification mode using an electronic crossover, which raises the obvious question:
What are the appropriate settings for the crossover?
Our initial starting point was with an 800 Hz, Butterworth, -12 dB octave setting for the midbass to plasma driver and a 200 Hz, Butterworth, -12 dB/octave for the bass to midbass driver.
The acoustic polarities all match now, and am trying to figure out how to set the relative delay settings, which is not the easiest of issues.
The speed of sound is based on three variables: the adiabatic constant of gas, the molecular mass of gas, and the temperature.
Using a handheld IR thermometer to measure the temperature, the majority of measurements were around 460 degrees F at the center of the plasma after warming up.
When striking it’s around 250 degrees F and I did get a few edge readings of the plasma at 650 degrees F. Room temperature was 75 degrees F.
In a pure helium environment, this calculates out to 4,316 ft/second. A bit different than the 1,132 ft/second of air. Obviously the gas in the chamber is not pure helium either.
My next step is to make some impulse measurements (ETC) of the system and observe the differences in arrival time between the three drivers.
Dr. Hill working in the lab.
Download the Service Manual: Plasmatronic Service Manual
Keeping a pair of 35 year old Plasmatronic 1A system running is clearly not the easiest task in the world. It involves learning about gas distribution, vacuum tube power amplifiers, control systems, and some strong lifting abilities.
Yet when you break it all down, it does make sense and will work. The key is patience.
As an aside- I was stuck on an ignition problem for months. After actually reading the manual I was able to fix the problem in thirty seconds.
Tools recommended are a strong back, a good table with proper lighting near your speakers, a pair of thick oven mitts (really handy for carrying the plasma units), some Caig cleaning products, a gaggle of Q-Tips for cleaning, and a tolerant support partner.
We recently resurrected our set (30 L and 30R) after a twenty year hiatus. I removed both the original cone drivers and replaced them with a Dynaudio midbass and Audio Concepts AC-12 subwoofer at the recommendation of a good friend and industry colleague.
You’ll need a good soldering station, pipe tape, Allen wrench set, adjustable wrench for the gas connection, access to a tube tester, a roll of trimmable velcro, and a couple of circuits of AC power in the room. The WT3 woofer impedance program ($99) made short work of the cone related issues.
As a non-general rule with the disclaimer (it’s your house, don’t burn it down)- you can operate the system on a single 20A 120V circuit. You will need at least two plug strips- one for each speaker- as two on a strip will trip the internal breaker on the strip.
I would also recommend using a triamplifier configuration and bypassing the internal Passover between the woofer and midbass unit.
We are currently a Yamaha SP2060 is upstream of the Hill Interface Unit in our system feeding a tri-amplified configuration in our system and bypassing the internal passive crossover. We selected the Emotiva 5 channel 200 watt amplifier; only using four of the channels. It has balanced inputs, good protection against faults, plenty of current (never approaching clipping) and drives the mid bass and subwoofers nicely since it is only used up to 700 Hz. Speaker wire is some Mogami sourced 10 AWG for the subwoofer and 12 AWG for the mid bass, primarily so as not to confuse which was which.
Currently the Yamaha crossover has the low end driver is configured with a Thru High Pass Filter at 20 Hz, and a Low Pass Filter at 100 Hz, -12 dB Butterworth.
The midbass driver is High Pass Filter at 100 Hz, -12 dB Butterworth. It is High Pass Filtered at 710 Hz, – 6 dB. I have electronically inverted the polarity, but frankly the difference is minimal. It is delayed 2 mS relative to the bass driver
The high frequency driver is set at 710 Hz, – 6 dB per octave. It is delayed 1.5 mS relative to the midbass driver.
A good room fan is important. I chose a Vornado model which is relatively quiet and discretely placed it out of sight.
My son chose Pink Floyd’s Wish You Were Here for first listening, and frankly we were stunned. I’ve listened to that disc since it first came out, went to the LA concert performance of it in my youth (yes, the infamous Darryl Gates debacle), and still heard things on it I’ve never heard before today. I have written over 350 audio articles in my career, and frankly do not have the words to describe the difference between listening on the Hills and any other system. I only wish I had the listening acuity of my youth back.
We have five audio systems in the house- an all Quad electrostatic system, two Gale GS401 based systems, and one Sonus Faber system and they are well loved and appreciated. I regularly go to CES and the local Hi Fi show and have compared with the best Wilson and Magico have to offer. All marvelous kit- but…
But as Lynn Olson once wrote, they are all 737’s parked near a Lockheed SR-71.
Probably like watching the 1927 Yankees play the Red Sox. Hey, someone had to go 51-103 for the Yankees to win all those games. The Quads do some things better than the Gales and vice versa. The Sonus Fabers also have their strengths. But the audio quality of the Hills is superior in every aspect.
If you were to ask me the most common failure issue with these speakers, of all things it boils down to a silly little resistor. Symptoms include one of the five electrodes will not light, the front panel meter gives you silly readings, and the indicator lamp remains lit constantly.
Each speaker houses five tube amplifiers within based on the 6MJ6 (also known as a 6JE6-C) Beam Pentode vacuum tube. This tube was generally used for TV horizontal deflection amplifier applications back in the day, but it is a seriously robust tube with thicker glass.
The anode of each tube feeds a large vertically oriented green ceramic 25 KΩ 100 Watt wirewound resistor. Directly underneath that big green resistor on the opposite side the printed circuit board is a 1.75 KΩ 5 Watt resistor which connects directly to one of the five tubes feeding the plasma chamber. That’s the troublemaker. You generally have to unscrew the P.C. board to access them.
I have had THREE of these 1.75 KΩ resistors fail (there are ten total, five per speaker). Originally made by Clarostat (Model VPR5), they end up overheating and cracking down the middle. You can get NOS replacements online, but I’d suggest an alternative to these little devils. They overhead, the internal wiring blows, and they crack in the middle. Here’s a photo of two examples…
My suggestion is two-fold. Replace them with a higher rated wattage resistor (10 watt ceramics are easy to find) and keep a few extras in stock. Schematically, the little devils are highlighted in rounded red rectangles below:
The right plasma started acting up a little bit. There was an intermittent (once every ten seconds) “chirping” sound which would make the bias meter oscillate wildly on one the five internal amplifiers.
The interesting part was the top electrode metal cap came off easily, and underneath the top of the tube was badly corroded.
Turned out to be a bad tube. Replacement sorted the problem out instantly. Always handy to keep a stock set in hand. They’re up to about $30 apiece for NOS on eBay now.
The lower segment of the left channel LED display wasn’t working. Turned out one of the ground traces on the display printed circuit board wasn’t passing ground. Soldered in a jumper to bypass the trace, and worked perfectly once again.
I would suggest replacing the Interface power cord as well. The original rubber jacketed version deteriorates with time.
I want to give credit where credit is due (one of our members forwarded this to me) but frankly can’t find the original email. Click on the image to enlarge, save it to your hard drive, and print it out.
Hill Plasmatronics Type 1 loudspeaker
By J. Gordon Holt • Posted: Jun 9, 2014 • Published: Apr 1, 1980
Dr. Alan Hill, president of Plasmatronics Inc., was previously employed by the US Government in laser research. His assignment: To increase the efficiency of lasers so that they could do something more impressive than produce holograms, mend leaky retinal blood vessels, and punch pinholes in steel blocks. Dr. Hill earned his keep, thus advancing laser technology a giant step closer to Star Wars, and then retired from government service to design. . . a loudspeaker?!!!?
How could laser research qualify someone to design a loudspeaker? The connection is really much more direct than it seems. Twenty-odd years ago, Dr. Hill envisaged a loudspeaker that would use a field of ionized air as the transduction element, but didn’t feel enough was known about plasmas (footnote 1) to perfect such a device.
At about the same time, a firm called the Dukane Company started producing such a device anyway: The “Ionovac” tweeter. It was not a huge commercial success, partly because of its (for those days) outrageous price and partly because add-on tweeters have never been big sellers. (The Ionovac was subsequently made by ElectroVoice until phased out in 1963.) Nonetheless, the Ionovac is still considered by the knowing to be the best supertweeter ever made, and there are few audiophiles who would sniff at its 2–40kHz (±2dB) response.
While developing the high-efficiency laser, Dr. Hill found it was necessary to control the shape of the plasma of ionized gas that does the lasing. And it occurred to him that shaping might be the key to a high-efficiency, wide-range “Ionovac.”
His first efforts, using a relatively low-temperature plasma (and an absolutely Mickey Mouse mockup), were disappointing. It produced sound, over a respectable part of the audio spectrum, but at ridiculously low levels of efficiency. Using higher ionizing voltage, and a mixture of air and helium as the plasma medium, he was able to sustain a much larger plasma field (thus significantly extending the low-end range) and to yield practical efficiency figures. Then it was necessary to do additional trimming of the system to produce the flattest possible frequency response across the board.
All Photos Courtesy John & Amelia Mayberry
In the final production version, flat response is maintained (with 1dB) down to around 700Hz. The upper limit is claimed to produce “significant acoustical power” out to beyond 100kHz. It was deemed impractical to try and carry the low end because of cost and power-supply considerations. Even in the production version, the required driving amplifiers (built into the system and all tubed) are rated at 500 Wpc.
The range below 700Hz is handled by conventional cone drivers: a 5″ midrange and a 12″ woofer, which must be driven by their own (choice optional) amplifier.
The speakers connect to the main system preamplifier via a 30′ cable and an “electronic interface”—a small box housing the system’s electronic crossover circuitry, balancing controls, and a series of LEDs that display the system’s output level at any given instant. The interface unit is located at the main preamp end of the interconnecting cable.
Gas Beside the plasma driving amplifier and the transduction device, each speaker enclosure also houses a large bottle of compressed helium gas (footnote 2), which is fed on demand to the plasma field when the speaker is operating. (When the system is off, the helium flow is automatically turned off.) The bottles must be recharged after each 300 hours or so of operation—representing s little under 6 months of 2-hours-a-day listening sessions. Refills cost around $30 per bottle, which translates into an operating cost of 20¢ per hour for helium alone.
For people living within convenient delivery distance of a major city, there should be no trouble locating a helium supplier. (You’ll find them in the Yellow Pages, under “Gas—Industrial and Medical—Cylinder and Bulk,” or under “Welding Supplies and Materials.”) For those people who live ‘way out in the boonies, recharging may involve shipping the empty bottles to some distant supplier and waiting, perhaps for weeks, for their return. (Anyone who can afford a pair of the Plasmatronics should certainly also be able to afford a second set of gas bottles to be put into use when the other set is away being recharged.)
Practicalities Each speaker weights about 300 lbs with its fully charged bottles. And when both amplifiers have been running for an hour or so, their combined heat dissipation dumps about 3500 BTUs (just over 1kW) into the room—dandy on those chilly winter evenings but a dubious blessing on a hot August afternoon.
With all the design complexity, the question of reliability must inevitably come up. As of now, the speakers haven’t been around long enough to establish ay sort of reliability record, although their ability to withstand accidental overloads and foolhardy listening levels has already been demonstrated. They seem to be very rugged, but whether or not production samples will be inadvertently sabotaged by a parts vendor remains to be seen.
Those of us who have read alarming things about the toxic effects of ozone may wonder how much of a problem it is with this system. Well, the Plasmatronics do generate ozone, but in such small quantities that after three hours of continuous operation, it could barely be smelled at a distance of 12″ from either speaker. This concentration of ozone is so far below the toxicity (or of potential damage to rubber and plastics) that to worry about it may be symptomatic of some degree of neurosis.
There is provision for biamplifying the two lower-range cones, but this is one of those rare instances where biamping is not recommended. The built-in crossover has phase-correction circuitry; electronic crossovers do not. As a result, biamping the Plasmatronics speakers introduces audible frequency-response irregularities (which are absent when their own crossovers are used), neatly shooting down the system’s remarkable blending of drivers.
Listening We auditioned two versions of the Type 1 speaker over a 3-month period. The first was early production, and while that part of the audio range covered by the plasma driver was impressive (more details subsequently), we were unhappy with the low end. The cones blended superbly with the upper range, but the bass was somewhat loose, floppy, and ill-defined. We were inclined to blame that on the driving amplifier, which was one we had never been enamored of: the Audio Research D-100.
Subsequently, Dr. Hill made changes in the cone portions of the system and also found what he felt to be a better drive amplifier for them (the Threshold 4000A), and that was the version of the system we auditioned for this report.
So, how does the current version sound? Quite simply, mind-boggling! One’s first reaction is that there is just no transducer there at all. You seem to hear through the system to the program source. Stereo imaging and depth are as well reproduced as form any system we have heard, and the most immediate response to all this is that the system sounds incredibly alive.
Footnote 1: To a physicist, a plasma is a volume of ionized gas. (An ion is an atom having more than or fewer than its usual complement of electrons.) The gas within a plasma has an extremely low density, relative to the gas surrounding it, Thus, when cool gas is heated to the plasma state, it expands in volume and imparts a pressure wave to the surrounding, cooler gas. Using an audio signal to vary the volume of the plasma produces the alternating compressions and rarefactions of a soundwave.
Footnote 2: Helium is inert, odorless, and completely harmless. Deep-sea explorers have breathed a 50/50 mixture of oxygen and helium for days at a time without any effects other than a comical raising of the voice pitches that makes grown men sound like Donald Duck. (Excluding nitrogen from the “air” prevents a nasty diving disorder called “the bends,” which results from the formation of nitrogen bubbles in the blood stream when a diver returning to the surface undergoes rapid decompression.) The raising of voice pitches is due to gaseous helium’s very low density, which provides less acoustic loading the vocal cords than does normal air, causing them to vibrate more rapidly.
Sonic details are reproduced with clinical clarity, which is dandy with superb source material but a liability with the majority of recordings. Bass is deep, tight, and gut-shaking, and the seams between the drivers are virtually imperceptible—quite an accomplishment in view of the fact that two of them are cones, with appreciable inertial mass, while the other, widest-range one is completely massless (footnote 3).
Without running any curves, we would guess the low end to be effectively flat to around 35Hz in a room of adequate proportions. (The one we listened in was not. The tightest, deepest low end was only audible in an adjoining room, which did at least prove that the system was capable of producing that kind of bottom.) Our only cavil about the sound concerned the system’s brightness, which was too much. Dr. Hill assures us that the system measures flat out to the bat’s radar region, and indeed it sounded flat when we listened with the cartridge of his choice (a GAS Sleeping Beauty Shibata). But with original tapes, and a cartridge we have found to provide comparable brightness, we felt the sound from the Type 1 to be brilliant almost to the point of stridency (although without the teeth-setting edge that betrays the presence of spurious odd-order harmonic content). For this reason, the system never quite captured the correct musical timbres of most musical instruments—an attribute few audiophiles seem attuned to anyway. (Take an audiophile to a concert and his first reaction is, almost invariably, “My God, where are all the highs?“)
With most speaker systems, some degree of exaggerated treble is necessary to help overcome the innate deficiency of detail. It is not necessary with the Plasmatronics, although we can well understand how that brightness may be necessary to sell these speakers to the kind of listener willing to pay $7000 for speakers alone (many of whom are locked into cartridges whose own brightness range is attenuated). If we had our druthers, we would like to see (and hear) this system equipped with a switch that would provide, in one position, the kind of sound that we heard (by which we cover ourselves against the possibility that it may sound less bright in other rooms), and in the other position,, a more neutral musically felicitous sound.
Considering the current chaotic state of the high-end” audio field, few listeners will get any real idea of what these speakers can and cannot do until digital program sources become more widely available. Anyone endeavoring to evaluate the Plasmatronics at a dealer’s will be at the mercy of the dealer’s often-misguided choice of associated equipment. There is, in fact, more than just a possibility will sound better than it really is, because of the current popularity of deadish but tipped-up phono cartridges that will tend to offset the speaker’s brightness and underscore its remarkable detail.
The Type 1’s literature specifies a maximum output level of 107dB, which looks pretty good but not outstanding. In truth, we found it possible to achieve clean signals up to a peak SPL reading of 116dBA before overload became audible. That may not be disco-type output level, but to any other listener it is one hell of a lot of noise—particularly when we consider that live music form acoustical instruments rarely exceeds 100dB when heard from an audience seat, even a very close one.
incidentally, “overloading” the Type 1 system does not cause the usual startling snap or crackle of amplifier clipping or voice-coil bottoming. When overloaded, the system—literally—runs out of gas and progressively limits the amplitude of signal peaks, in much the same unobtrusive manner as the peak limiters used for years by virtually all commercial record companies.
Conclusion Is this loudspeaker worth its $7000 price tag? Maybe. There is no doubt but that there is $6500 worth of technological know-how and constructional hardware in a pair of Plasmatronics Type 1s, but whether or not they are worth that much to you as a consumer depends on what you value, and how much. If you are hyper-critical of imaging, inner detail, transient response, and high-end openness, be assured that this system will give you more of those things than any other currently available system. If you are a bass freak, these won’t disappoint you, though they may not make you as happy as a large transmission-line system or a monumentally dimensioned horn system.
But if you are more of a music listener than a detail fanatic, you may well find that there is much in the grooves of most discs that is best left unheard. And if you are picky about the accurate reproduction of timbres, you may also—depending on the characteristics of your program sources—be more or less put off by the Plasmatronics’ brightness. We suspect, though, that most audiophiles will find these speakers to provide the most mind-blowing listening experience they have ever known.
Further Thoughts Although not the perfect transducer, the Plasmatronics Type 1 represents a significant advance in the state of the audio art because it eliminates, once and for all, the need for detail “enhancement” in the program material an ancillary electronics. If, and when, this standard of detail reproduction filters down into the lower-priced equipment areas, multimiking and the use of “hot” microphones to offset detail smearing in playback systems will no longer be necessary. This could pave the way for a new kind of audiophile recording, in which performing groups can be presented at a natural distance, to provide blending of the sounds without loss of definition. The result will probably be what we’ve all claimed to be seeking: The sound of live music. Whether or not we will all like that sound is moot. . .
Footnote 3: Well, not quite completely. The gas mixture has some thermal inertia, which causes a gradual rolloff of frequencies above about 30kHz. However, the rolloff is much less rapid than the rolloff that occurs above the resonance frequency of a mechanical transducer.
There’s are more urban legends surrounding the Hill Plasmatronics 1A than most any other speaker. Perhaps this is a result of so many wanting to hear a pair, but so few actually having the opportunity to do so.
Perhaps it’s time we some of the “legends” to rest.
False. “I was a dealer for Plasmatronics and have heard many wild tales about this speaker. First. It was not a health hazard. The odors produced by the arc were not ozone which I was told was not produced in quantities large enough to be harmful, said Dr. Hill, but was mentioned by jealous competitors to restrict sales of this speaker by making it appear as producing unhealthful gas.
I listened to them for over four years and suffered no ill effects. They did produce an odor, but it was not ozone. My demo room was not well ventilated and I can assure you that a man of Dr. Hill’s integrity would go broke rather than market a speaker dangerous to a person’s health!
You can bank on the word of Dr. Hill and my experience over several years as a reference to their safety. I have never seen a testimony or legitimate fact sheet which proved they were unhealthful. Some competitors and critics were simply uptight about the Hill accomplishment and resorted to untruths to defeat sales of this radical but ingenious design.” – Carl Miller
“That’s correct, virtually no ozone. Now here’s an example of something that made lots of ozone…” - Nelson Pass
False. According to one who was there, 52
pairs were built in total. Four
pairs were packed off to a disco in Singapore. Many of the others
were sent to California, Chicago, White Plains, and Coral Gables.
Hill always said most speakers were shipped overseas.
At one time there
were at least 14 pairs in the US. Thirty years on, who knows?
But we know of at least five sets still running in the USA!
“I owned 2 pairs, and one of my business partners had a third pair”- Nelson Pass