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Plasma Speaker, Plasma Chamber

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GhostNull

Thu Sept 09 2010, 11:31AM

Registered Member #2648 Joined: Sun Jan 24 2010, 12:45PM
Location: Australia
Posts: 291

Hey

How are plasma chambers made?
What is structure of a plasma chamber like?

I've done reasearch on commerical plasma speakers and have found that higher quality plasma speakers utilise a helium filled charmber for the ionisation of gas. This I think means that they do not give off much if any ozone. It also I think means that they are better at producing sound, due to the lower break down voltage of Helium and the chamber helping to amplify and direct the sound. I'm going to be making a plasma speaker and I'm considering maaaaybe making a plasma chamber. Problem is, I haven't been able find any information on how plasma chambers work.
I've attached my idea for a plasma chamber.

Corrections would be welcome

Thanks
-Ken

Patrick

Thu Sept 09 2010, 05:10PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

from my high school research i believe plasma is used for tweeter apps, due to low inertia, and therefore fast freq response, i dont know of an application of mid or low range freqs, it may be possible. you may be in uncharted territory. good luck!

Sulaiman

Thu Sept 09 2010, 05:37PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

I'm pretty sure the helium would diffuse away quite quickly,
you'd need some kind of helium-proof membrane across the open end to stop that.
The movement of the membrane would probably be less than one mm at practical frequencies.

Patrick

Thu Sept 09 2010, 08:36PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

my chemistry book reveals: He to have a average speed of 1350 m/s @ STP
N2 = 520 m/s
O2 = 490 m/s
thus, his "horn" must be quite long to keep them from effusing, remember K-M theory suggests that the rate of effusion is inversely proportional to the square root of its mass. but he should try anyway.

based on hiscurrent idea, with short horn, the He may dissipate in a few seconds or a few hours, its hard to calculate.

also, including a membrane defeats the whole purpose of a low inertia speaker device.

radiotech

Thu Sept 09 2010, 08:47PM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

The corona wind loudspeaker Gerald Shirley- June 11 1956 AES New York Section

DM Tombs Nature 176 923 ((1955) Dr Tombs thought radioactive needles would work best. Look at Shirleys curves. It was the 50's

Perhaps the internet will cough up these papers

Patrick

Thu Sept 09 2010, 09:27PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

radiotech wrote ...

Dr Tombs thought radioactive needles would work best... It was the 50's

geez radiotech, you say "Radioactive" and "the 50's" like its a bad thing, love canal (pcb's), rivers burning (benzene) and Dr. Strangelove (nuclear war), you worry to much radiotech.

hmmm...radioacive needles...

EDIT: thats a great scan doc, the corona speaker is like a DeSeversky lifter, but made to be by directional.

radiotech

Thu Sept 09 2010, 11:25PM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

The needles are fun as sources in cloud chambers. The Plasma design that GhostNull proposes is a horn and a horn is an acoustical transformer with throat loading issues.

We are not suggesting a nuclear powered Klipschorn to solve the response issues.

Adam Munich

Fri Sept 10 2010, 03:43AM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

Often small neon bulbs will have thorium coated electrodes. You should also try thorated tungsten welding rods. It won't melt and may make a difference, be it ever so slight.

Patrick

Fri Sept 10 2010, 04:24AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

radiotech wrote ...

The needles are fun as sources in cloud chambers.

This is a great point, I forgot that radiotech!

GhostNull

Fri Sept 10 2010, 09:58AM

Registered Member #2648 Joined: Sun Jan 24 2010, 12:45PM
Location: Australia
Posts: 291

Thanks for the Replies,

Looks like the helium diffusing would be the biggest problem, but in the final product there would no problem having a canister of helium to countinually top up the helium in the chamber unless I get heaps of helium diffusing.

And as for thorated tungsten welding rods, I think it would be more trouble than it's worth. From what I've seen tungsten, espcially with impureities is very hard to work and I haven't done any real metal work before. My plasma speaker it's probally going to be Dr. Kilovolt's circuit and even if it's not I doubt I'll go over 200w, it's not going to be a kW SGTC, so I don't think melting will be a problem. The amount of thorium in weld rods will most likely have little effect as you said, Grenadier. So thorated tungsten welding rods would be more trouble than it's worth. but hey, I could be wrong

My main concern is about the construction of the plasma chamber and making sure it sufficiently holds the helium.

I'm thinking of making the chamber by:
1. Making an open box out of some non-conductive material,
2. Lining it with plaster of paris
3. Drilling holes for electrodes and horn
4. Placing a piece of glass on for a veiwing window
5. Sealing it all up with...something, Suggestions?

My ideas for materials at the moment are:
Plexi for the structural box, since it's widely availible and easily workable. Any suggestions?
Steel for the electrodes, since it's tough, widely availible and workable. Any possible other metals that are easily workable and durable?

As for the horn I'm thinking one from a gramma phone with the curl in it would be good. The curl would help hold the helium and mean I could have the horn facing outward rather than down.

Could maybe another gas be used instead of Helium?

Suggestions would be great.

Thanks
-Ken

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