Plasma Speakers and Flame Speakers

[cotdt]

I've never heard plasma speakers myself but a have friends who have heard them and claim that they are the best they've ever heard, with better highs than even ribbon tweeters and great midrange and bass as well, with amazing detail. According to my friend, they don't seem to have any tradeoffs or weaknesses at all except for the minor fact that they emit poisonous gas as they play and bursts out helium when you turn them on. Anyone ever heard one? I've found this on a speaker design website:

http://www.nutshellhifi.com/library/...r-design1.html

"No resonances at all, and accurate pulse and frequency response up to 100kHz or more. Low distortion too ... like a really good amplifier. Actually, the "diaphragms" do have mass. But it’s not much. It’s the same as the surrounding air, so the acoustic coupling is 1:1. The efficiency is a little difficult to state, though, since the output tubes of the power amplifier are supplying a high voltage that directly modulates a conductive gas with very complex electrical properties.

I first heard the Hill Plasmatronics at the 1979 Winter CES, and I must say I've never heard a tweeter that even came close to that one. The exhibitors darkened the room for dramatic effect, and you could see this weird violet glow through the grill cloth that looked for all the world like a gassy triode ... but it was the tweeter! Not only did it glow, it pulsed along with the music!

The rest of the speaker, though, was a pretty mundane paper-cone setup in a huge cabinet ... oh well. Even so, the Plasmatronics was a wild thing, a taste of the future, like a SR-71 Blackbird in an airport full of commuter-shuttle 737’s. Not too surprisingly, the inventor was a plasma physicist at Los Alamos Labs.

(Talk about being ahead of your time! This was 10 years before the fall of the Berlin Wall, and Dr. Hill was already thinking of ways to peacefully convert atomic swords into sonic plowshares!)

There are a few little problems with this glimpse of Paradise. Previous generations of plasma speakers, such as the DuKane Ionovac tweeter of the Fifties, used RF heating to ionize air, making it conductive. There’s a problem with this. If you ionize air, some of the oxygen molecules (O2) are stripped apart and then recombine as ozone (O3). You also get nitrous oxide (NO2), which is formed by combining nitrogen and oxygen at very high temperatures.

Well, a dose of laughing gas may or may not enhance the listening experience, but ozone really isn’t too healthy, since it irritates and burns the mucous membranes and the eyes. The natural home for these highly reactive gases is far up in the ionosphere, not in your living room.

The Hill Plasmatronics avoided the air pollution hazard by having its own built-in supply of helium, which is a noble gas and thus unreactive even when ionized. Helium is also biologically inert, and being much lighter than air, promptly escapes to the upper atmosphere and outer space. Even in the best-insulated houses it will be gone in a matter of seconds, so it is completely safe.

I remember seeing the helium tank, pressure gauges and all, in a special compartment inside the subwoofer enclosure. Imagine cracking a valve and hearing a very faint hiss of helium gas every time you turn on your hi-fi. Oh, I nearly forgot, you had to swap the helium tank for a fresh one every month. Helium is not a renewable resource, and is only found in a few natural gas wells, so it’s not as inexpensive as other industrial gases.

There are still some interesting plasma-speakers that haven’t been tried yet. For example, one alternative to tanks of helium is a flame speaker (flames are plasmas too), using flammables that release no toxic byproducts of combustion. This leads us to hydrogen and oxygen, preferably generated on-the-spot by splitting water by electrolysis. (You’d water the loudspeaker like a plant!) The hydrogen and oxygen pipes go up to a copper wire mesh (a hemisphere would be the right shape), and the flame is trapped on the surface of the copper mesh.

The system has a computer-controlled power supply that splits the water, monitors the gas flow, and automatically sparks the flame when the correct hydrogen-oxygen ratio is reached. You then polarize the plasma with a high-voltage supply and modulate the flame with a high voltage audio transformer or direct-couple to 211, 845, or 212E plates from the built-in power amplifier. (The flame is modulated in the same way as a conventional electrostatic speaker.)

As far as I know, nobody has ever built a complete system like this before. I hereby throw the idea into the public domain, and wait to see if anybody is crazy enough to actually build it.

Don’t expect to get UL or VDE safety certification for a "loudspeaker" that mixes hydrogen and oxygen gas, high voltage, distilled water, AC power, an open flame, and a microprocessor, all in a domestic environment. Imagine the reaction of the reaction of the insurance company if they discovered how it works!

Aside from these trivial non-audiophile considerations, the plasma-flame speaker would have truly exemplary performance ... very low distortion, perfect impulse response, and a bandwidth of 100kHz or more. Another benefit of the confined-flame speaker is the "diaphragm" can be as big as you want, limited only by concerns like combustion noise, room heating, and fire hazard. As a compromise, a 6" diameter hemispherical flame front certainly wouldn’t be too difficult to build. That would deliver response down to 200Hz or so. It would be lab-standard flat from 200Hz to 100kHz, and no cabinet resonances either.

Just imagine a cold winter’s evening with twin pale-blue flames illuminating the copper-mesh hemispheres, the faint hiss of hydrogen & oxygen gas, the quiet murmuring of the water electrolyzer, and a pair of eighteen-inch-high Western Electric 212E direct-heated transmitter tubes to make it all sing. Add a Jacob's Ladder for visual stimulation and the picture is complete; Bride of Frankenstein has an electrifying night over at Nikola Tesla’s bachelor pad. Careful with that Zippo lighter, Nick!"

Edit: The bass doesn't come from the plasma speaker but a separate subwoofer, according to friend.

[cotdt]

Here are some pics:
http://www.plasmatweeter.de/plasmatronic.htm

[cotdt]

I haven't gotten to the amazing part yet. The amazing part is, someone actually installed one into their compact car and it still has 4-seats and a trunks like a regular car.

[demon2091tb]

Ok wow....that really was ahead of its time....and still is i'd think.

I just read your post but i really want to go back and read that link....VERY intresting and unusual, but i wonder how it would compete with some of the newer technology today that we have....still as good if not better?

[SQ_Bronco]

Definitely more fun to watch.

here's a diy setup: http://www.angelfire.com/electronic/...s/tweeter.html

[cotdt]

Nice find, there is also this site:
http://www.plasmatweeter.de/eng_plasma.htm

The gases produced isn't too bad:
"One thing on the end. The speaker produce OZON. Normaly this is a radical and dangerous to your health but with the little amount the tweeter can produce there is no danger at all. After hours of operation you smell it in the air in closed rooms. Open your doors and it is away. So good luck if you want to build it and let the Ionic Force be with you."

[Ludemandan]

A speaker you can read by!

[chad]

Well, because IE hates me quoting, this is in respopnse to the DIY plasma tweeter:

Woah, you build one of these and you will probably get a visit from the FCC. An EL509 has a max plate dissipation of around 200W PEP. 27MHz is sitting right in the CB band and not far from the 10M and 12M ham bands. A 4W CB has a range of around 4 miles on a bad day with a decent antenna. Also keep in mind that the second order harmonic of 27Mhz is smack in the middle of the VHF TV bands. TVI on such a device would be horrendous, especially since it's a HEAVILY modulated device. Granted the radiating device (antenna) would suck but at 200W you can wreak havoc for blocks!

Please see for freq allocations:

http://www.ntia.doc.gov/osmhome/allochrt.pdf

Keep in mind that ANYTHING that will creep into the area of 26.965 - 27.405MHz MUST be FCC type 95 accepted, the fines are quite heavy ESPECIALLY at 200W where you are ONLY allowed 4 watts. Don't mess with these folks! Remember that someone "OWNS" damn near every frequency out there, if you interfere with transmission it could not only mean someone's life but some unfortunate financial responsibilities for you. Check out AARL's log of people with "Incidental Radiators".

There ARE open freq spots, you CAN use them, but filtering must be as such to not interfere with anyone else. If you consider building one of these please enlist the help of a well educated amateur radio operator who can help you select proper carrier frequency selection and bandwidth.

Just a message from your "old uncle Chad "

Chad

[cotdt]

Wow so the FCC will come after you also...

[DS-21]

Acapella gets around the hazards by putting the pulse behind a ring of material that catalyzes the conversion of O3 to O2 - I assume, because I wouldn't imagine that singlet oxygen would be any better than ozone - and for better or worse I have to confirm that the sweetest, most extended "just there" treble I've yet heard came out horn with the purple pulsating dot in the Acapella Violon 2000. It seems to work, because after a long time (a Shostakovich symphony, most of a live Stevie Ray Vaughan set, and at least half of Bela Fleck and the Flecktones' Live Art) there were no untoward odors in the room. However, I heard them in a properly-built brick-and-concrete Austrian room; in a room constructed of spit and cardboard norm of American construction over the past 30 years or so, perhaps the treble would be voiced too politely.

If it weren't for the peaky, nastly, bloated bass alignment of those speakers (perhaps fixed in the newest version, which uses a sealed bass alignment, though I've not had a chance to sample it) I'd consider the Acapella Violon 2000 one of the top two speakers I've yet heard. For EUR20k, I'd prefer not to have to do an reëngineering, though...