Plasma is the most elusive of the four states of matter in physics; there are solids, liquids, gases, and well, plasma. Heating a gas in a strong magnetic field leading the molecules to dissociate or fall apart into individual atoms with electrons either added or removed creates plasma. These ionized plasma particles have some rather fun properties. Anyone who's ever been struck by lightning might have experienced some of those.
Now one might think that plasma might be a rare and precious thing, but it is in fact by far the most common state of matter our universe holds. All stars are essentially made of plasma.
Why are we talking about this on a blog about anything slash everything audiophile and loudspeakers? Well, arguably the most extravagant way to reproduce sound is by means of plasma speakers.
To cut to the chase: The question many audio enthusiasts will ask is: "but are these things loud enough"? Well like anything in high end audio this depends on the effort put into their making. The guys at ArcAttac use two huge Tesla Coils to create an arc that is powerful enough to raise hairs in any venue in Vegas. The suit acts like a Faraday cage to keep the player safe by directing the electric arc through the conducting suit and into the ground and not through the players body. Don`t try this at home. I already know some of you will....
The first person to ever find a way to use plasma to reproduce sound was a rather obscure fellow named William Du Bois Duddell from Britain,, who was a physicist and electrical engineer but above all a gifted scientific instrument maker.
Around the turn of the last century and before the invention of candescent light bulbs, arc lamps were used to light streets and buildings. A plasma arc was created between two carbon electrodes. The problem with these lights was that they tended to make some rather nasty sounds described as humming, hissing and in some cases a rather disturbing howling sound. Duddell, as a young student of electrical engineering was asked to look into this and realized that the sounds were caused by instabilities in the current driving the plasma arc. Now Duddell seemed happier doing weird stuff than fixing the problem, but in the end he managed to do both. Born of Duddell's experiments was a gimmick called the singing arc.
By carefully tuning the frequencies and inventing a rudimentary keyboard he was able to perform “God Save The Queen”. Now, had Queen Victoria actually attended a performance of such, her experience, far from feeling “saved” might have been one of mild nausea or even intoxication; the presence of nitrogen and oxygen in the air leads to some rather nasty things when exposed to a plasma arc like ozone or nitrous oxide. Unbeknownst to most, by his childlike pursuit of curiosity, Duddell became the great pioneer of synthetic and electronic music.
What happens inside a plasma arc that produces such sounds is the rapid expansion and contraction of the gas as plasma is created leading to vibrations.
There are a select few fantastic reasons to build plasma loudspeakers, and then there is a compellingly long list of things that might also make you want to stay away from such an endeavor.
One great reason is that for all practical purposes they can be considered mass-less speakers. When it comes to transient responses, this is of course the utopia we high-end loudspeaker designers are after. The waterfall response curves are unatainable with anything that has a moving mass and if this were any less difficult or dangerous to make, I think they might just make their way into BestBuy.
No mass... Love it. A couple of attempts were made to produce commercial products: The Ionovac / Ionofan came out in the 50s and was at 78 pounds rather accessible, but it suffered from very high audible distortion. According to Wikipedia, this design is still available through a German company as a DIY kit, but I could not find any solid references.
Back in 1973 a company called Plasmatronics founded by Air Force Weapons Lab scientist Alan E. Hill offered a rather stunning contraption. In a praiseworthy attempt to not poison the audience, he solved the problem with toxic gasses by using gas from rather large helium cylinders to create the plasma. As this technology only works for frequencies in the Tweeter range, conventional mids and woofers were used. While praised for its high accuracy in sound reproduction, the Plasmatronics Type I never quite made it into the homes of very many. Reportedly 60 pairs were sold at a price of $10,000 each.
One actually great application of plasma speakers was as test equipment for ultrasonic microphones or otherwise as ultrasonic emitters. The Plessey Ionophone made in the 1960s by Sonotone Corporation was just such a device.
Now come the great reasons to stay away from this technology that have led to an almost complete non-existence in the market with the exception of one company offering do-it-yourself kits to those who actually insist on trying things that they are asked to not try at home, at home. Not an easy sentence to get through, I realize.
One is the afore mentioned necessity to either carry large cylinders of inert gas, or live with varying levels of intoxication. Fire hazards are also a great reason to stay away from these. Plasma speakers will always be restricted to frequencies higher than 800Hz and thus require conventional compliments.
After all is said and done, plasma speakers have gone the way of the Dodo but I honor all those like us at KVART & BØLGE passionate enough about sound to walk the improbable road to perhaps stumble upon the remarkable. It is that kind of passion and enthusiasm for unconventional solutions that makes our audiophile hobby or profession worth pursuing in the first place.
Arved Deecke is founder of the Danish / Mexican Loudspeaker company KVART & BØLGE that makes audiophile quarter wave loudspeakers and sound systems at a price anyone can afford. In his free time he blogs about all things related to sound, music and audio.
