Cold Plasma Speakers

Go to the nearest blood bank; that's what they use in their freezers.

Bob M.

Can't you use Google?

No luck

I ask because I am looking for a type of speaker that does not use a diaphragm and does not get too hot to touch.

LMAO !

Hey, I've met your namesake Archimedes Plutonium recently. He's as barking mad as you are !

Graham

Strange that isn't it ?

Graham

AP's still around? Yeesh! Ain't seen him in forever! (Not that I've WANTED to, but...)

"Radium" wrote in news: snipped-for-privacy@m79g2000cwm.googlegroups.com:

Any electrosttic or piezoelectric speaker should work for you.

Angelo Campanella

Angelo Campanella wrote in news:CcQDg.607746$ snipped-for-privacy@bgtnsc05-news.ops.worldnet.att.net:

Both electrostatic and piezoelectric speakers require/utilize a diaphragm to produce the required SPL.

I don't think there is such an animal, today. There have been a few plasma loudspeakers sold. One of them was by Plasmatronics (in the early 80's, iirc), however, they weren't "cold". It used an inert gas (helium, I believe) to create 'fingers' of plasma. Each finger was about 3" long and glowed bright blue. This was only for the upper midrange and highs, and the need for a large tank of helium was a real pita, plus the low end was a conventional dynamic speaker.

I was also fortunate enough to have seen and heard one that did not (apparently) use an ignited plasma. It didn't play too loudly and was never produced commercially. It also created large amounts of ozone. It had response down to dc. Its mode of operation was probably similar to those plasma-based air cleaners. I've considered getting one of these air cleaners, then apply the appropriate modulation, but I don't think it would produce the type of sound that would sell (plus the ozone problem is still there).

Here's a link that may give you some more info.

Bob

Here:

All efficient speakers will use a diaphragm. If efficiency can be sacrificed, then the bare piezoelctric can be used.

It is my undersanduing that electrostaic speakers are flat and are all transducer (or all diaphragm if you declare that the element itself is a diaphragm).

Ang. C.

Hadn't Elac a plasma tweeter? Not cold, of course. And after playing Dark side of the Moon there was so much ozon in the room it caused lung diseases. :-). Why are we taking this Radium serious?

Angelo Campanella wrote:

The device was born as an "ionophone"; a classmate in the '50's (Fuji Oda) built and evaluated one as his masters thesis around 1955.

He had to make the transducer itself from fused quartz because it ran white hot (about a kilowatt of input power; as an RF carrier at 27 mHz.

The transducer shape was basically like an eyw cup with an electrode on either side wall, connected dorectly to the output transmission line from an RF transmitter. Amplitude modulation (AM) of the rf carrier produced sound and some light from the plasma and hot quartz at the time for that coonfiguration.

Ozone; yes.. smelled it often.

Plasma TV screens use a low pressure gas sealed in an envelope. The gas glows when milliamps of current flow through it. The place where the glow occurs is around the cathode or anode (I forget which) in the case of DC current. If AC current is used, both glow alternately. Such gas discharges are highly nonlinear; there being no current until breakdown occurs, the abundant current and light. That's why an AC carrier, which can be modulated at an audio rate, was used in the beginning.

The audio performance is entirey due to the expansion of the gas being heated by the quantity of current flowing through it (I^2*R heating). On an audio wave peak, the temperature and volume are greatest; on an audio wave valley, the tempreature and volume are least. I think it is really a clumsy way of productings ound, inherently nonlinear for moderate to loud sound levels.

That's what Fuji concluded.

Yup.

It's just a toy.

Ang. C.

Normally one doesn't.

Graham

Guys, he's a troll, ignore him!

I am not sure I should be posting on this thread but just a couple of points that may be of interest.

Plasmas in air have two mechanisms for directly producing sound. The first is a monopole caused by expanding/contracting due to a varying temperature and the second is a dipole caused by varying the stream of charged particles rapidly moving between the electrodes and transferring some of their momentum to the particles of air.

There have been a number of commercial designs of plasma speakers over the years and several DIY projects which can be found on the web. I believe a hifi company in Germany is still producing a tweeter for the "audiophile" market:

The principle of operation is nonlinear but then so is electrostatic attraction/repulsion. If the pros outweighed the cons I suspect engineers would find ways of handling the nonlinearity. However, it is hard to see an application where the cons do not outweigh the pros.