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Plasma Speaker, Plasma Chamber

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Patrick

Sat Sept 11 2010, 04:12AM

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

why did you fisrt specify helium? was your choice merely a desire for a noble gas to limit eletrode side reactions?

GhostNull

Sat Sept 11 2010, 07:05AM

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

I mentioned helium because that's what appearres to be used in most plasma speakers. I'm sure exactly why helium is used but I put my thoughts down on the orginal post

radiotech

Sat Sept 11 2010, 08:53AM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
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The sound, say 1 metre from the opening of your speaker is compression and rarefaction of air mollecules, as is all sound.

How does the He plasma modulated by the audio get coupled to the air in the horn throat?

GhostNull

Sat Sept 11 2010, 11:31AM

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

To be honest I never really understood precisely how plasma speakers work. Maybe someone with better knowledge could explain *looks at Dr. Kilovolt*

My current understanding is that plasma speakers work by varying current through the arc,
by doing this it causes the intensity of the plasma to change
The rapidly varying plasma/arc causes the compression and rarefaction of air molecules

The He molecules would interact with the normal air molecules passing on the sound. Ah I see, since the He is less dense than normal air it will give the sound a higher pitch, just like when people talk with helium.

Thanks =D

I guess that means I would need compensation kind of compensation =/ Any ideas?

radiotech

Mon Sept 13 2010, 02:40AM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
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Ghostnull Wrote.
The He molecules would interact with the normal air molecules passing on the sound. Ah I see, since the He is less dense than normal air it will give the sound a higher pitch, just like when people talk with helium.

I dont know if that follows.

An AC signal, like a sin tone has to find a way to move the
air in a bipolar way. In a moving coil loudspeaker the polarity
comes from the attraction/repulsion of the magnet to the moveable coil. Leaving the iron pole piece in place, if the magnet is taken away, the speaker will still work but double frequency of the the
acoustic.It goes into a square law mode where the current has to both generate a field in the pole as well as in the coil. The electrostatic speaker analogy is similar, only the polarizing is done by the DC bias onto which the AC is modulated.

So that would be a starting point, what mode of induction heats the gas? Now you have a gas on ions. That is an electrical conductor. From there you could reverse engineer a magnetohydrodynamic generator.

You could start with a propane jet, and a way to seed the flame and experiment with a MHD. to lay the foundations of making your plasma emit sound. The internet knows how these classlab kits work
if you can get it to tell.

btw Gramaphone horns sounded lousy untill telco types found out some physics and fixed them. Your's wont I hope.

Patrick

Mon Sept 13 2010, 03:15AM

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

radiotech wrote ...

Ghostnull Wrote.
The He molecules would interact with the normal air molecules passing on the sound. Ah I see, since the He is less dense than normal air it will give the sound a higher pitch, just like when people talk with helium.

I dont know if that follows.

yeah, the purpose of a tweeter is to give the high freqs as the mids, and woofers, find it difficult to move that fast. the plasma tweeter doesnt provide a difference in tone, its just like a piezo, you dont need compensation. ghost null failed to understant my point in the previous post. its not at all like inhaling a balloon's helium and getting a squirells voice.

okk

Mon Sept 13 2010, 08:45AM

Registered Member #2821 Joined: Fri Apr 23 2010, 04:57AM
Location: Beijing
Posts: 5

Hello all friends:
This is a good topic, that I interested in for a period.
As a sound source, the plasma flame enveloped by a chamber, connected to a horn, a plasma tweeter built.
In the traditional plasma tweeter with chamber (made in last 50-60's and used up to now), they did not fill any He. And the modern commercial plasma speakers(for example Acapella or Corona in europe) also did not fill any He. Actually they make O3 very little, because the voltage for keeping corona is very low (hundreds volts), so they can be survival.
But the tesla coil project gives much higher voltage, so it'll make much more O3.
I think the key-point of chambered plasma tweeter is chamber itself. I have not find any Patent about chamber of modern commercial plasma speakers. Somebody can recommend something to me?
Thanks.

GhostNull

Mon Sept 13 2010, 10:22AM

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

Patrick wrote ...

How did I misunderstand it? ='(

Patrick

Mon Sept 13 2010, 02:24PM

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

its not the He that gives influences the sound, dont bother using it.

GhostNull

Tue Sept 14 2010, 08:25AM

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

Then why do they use it in some commerical speakers?
I guess it's not worth the trouble in that case.

Thanks...

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