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In Reply to: RE: Plasma has mass. ????? posted by Ugly on March 15, 2008 at 21:59:55
"n some cases it might be low mass as in the case of air. It's still the same molecules there just now the nuclei have had the bond with all their electrons overcome. It's not like they suddenly get zapped out of existence. "
Obviously but for all practical purposes it has essentially no mass. A flame of 8 mm is roughly cylindrical with about 3mm diameter giving a volume of 56.54 mm2. Given 1 atm pressure and room temperature (298K) and using the ideal gas law, PV=nRT we can calculate the number of moles of air molecules (obviously air is a mix of gases but we can estimate this way). The calculation gives about 82 ng mass if you assume the mass of nitrogen molecule (28 N2). So if that is not close enough to zero mass for you then I am not sure what is.
Follow Ups:
"So if that is not close enough to zero mass for you then I am not sure what is."Close enough to zero for me? WTF does that come from? Are you mad at me?
No actually it is not at all close enough to zero for me. In fact finite mass is exactly what makes these plasm speakers interesting. The finite mass of the plasma is quite important in the case of the performance of a flame speaker, or any other type of speakers for that matter, due to the level of impedance matching in the driver to air interface. Luckily for flame speakers they have the same mass as the air surrounding them and therefore have nearly perfect impedance matching with the air. This is an extremeley important distinction in that with perfect impedance matching you could theoretically get get maximum power transfer whereas with a zero mass driver trying to drive finite mass object such as air you will get zero power transfer. You could say this detail is the difference between the loudest speker ever created and one that can't be heard by even the most sensitive measuring devices.
Edit: obviously there are more benefits to matched impedance than max power transfer, but that is one example of a possible "improvement" which might be had with this tech.
No I am not mad, sorry if it came across that way. I see the point you are driving at now and I would tend to agree with you. My point was that it is much lower mass than any other kind of driver so this is a good thing. Also, since it has essentially no structure it has essentially no resonance either. You are right about the coupling but also I have noticed that the majority of the plasma drivers are horn loaded, which can color the sound and is obviously necessary to achieve an adequate sensitivity.
Have you heard speakers with ion tweeters? When driven with really good tube gear the highs are simply the best you will have ever heard.
"No I am not mad, sorry if it came across that way."
cool!
"Have you heard speakers with ion tweeters? When driven with really good tube gear the highs are simply the best you will have ever heard."
No I haven't but I wish to do that one day. The whole idea, which BTW I've only just read a little about, sounds good enough to my only knowing enough to be dangerous self that I can believe they must be pretty good for upper band sounds. This thread has been causing me to wonder why this isn't more popular as a tweeter tech. Obviously there are tradeoffs preventing them from being full range but then what driver doesn't have it's own tradeoffs? The benefits of the the percieved performance in areas that conventional technologies really fall apart badly seems to make them to good to ignore, eh?
"This thread has been causing me to wonder why this isn't more popular as a tweeter tech"
Well as it is not really a driver in a physical object sense then the resaon boils down to the electronics involved in generating a plasma. It is essentially a high voltage RF torch that is driven by tubes and needs a much higher degree of knowledge than a conventional driver to design, build and implement. As an end user of course there or off-the-shelf options but they become prohibitively expensive meaning that they won't find wide acceptance into lower priced systems.
You guys have formed an interesting thread and clearly both know far more than I about ion tweeters. I did a quick Google and what I found were modulated Tesla coils. At least I understand part of that technology having built spark-gap excited ones as a teeny. Talk about EMI generators...
Is it correct that the coupling mechanism of the tweeters is heat? I remember that some used to use He which I think was to keep the plasma away from O2 to avoid generating ozone. If that's the case it seems to me that the interface of the He to air interface which has ~ a 3:1 density mismatch would cause reflection problems.
If indeed the mechanism is heat then why isn't the drive asymmetrical due to the Carnot efficiency being higher in the expansion phase?
I'm not likely to actually use them but I am curious.
Thanks, Rick
They are working in a very similar manner to a type of scientific instrument called an inductively coupled plasma (ICP). It is essentially a high frequency/high voltage power supply exciting a gas to make a plasma. The intensity of the flame is modulated by the audio signal.
I'm afraid I'm not familiar with any devices of that nature.
What is the mechanism that couples the modulated flame to the air?
Thanks, Rick
howdy Rick. Now don't be to hasty with your assumptions about me being knowledgable about stuff cause that'll leave you looking silly. I really wasn't aware of commercially available products until morricab brought it upand had just had my interest piqued many years ago fresh into my first position. One of the guys that was sort of mentoring me at the time was a bit eccentric and told me about flame speakers and showed me a short article on them. I'll definitely have to defer to morricabs greater experience with the commercially available stuff and the designs they use but I did find this old popular electronics article when I did a search.
I'm going out into not well understood territory her so please bear with me. High voltage induced spark gaps always have a bunch of acoustic noise with them even unmodulated. Why? I am unsure. Probably due to some rearranging of molecules for thermal reasons...don't know for sure. On the other hand chemical reaction flames can be pretty quiet when unmodulated. When the flame is something like burning wood you even get great impedance matching with the surrounding air. I can't explain why one flame type is quieter than the other but it seems obvious why one type might yield more pleasing results.
Here's a link to a DIY plasma tweeter:
http://www.ee.vill.edu/~cdanjo/plasma.html
Below is a link to Ulrich Haumann's DIY plasma tweeter too!
Thetubeguy1954
A Rational Subjectivist
This is not only a horse of yet a different color, but one I've never heard of. Or heard. Thanks for the article! I guess there must be a huge number of things that can be be modulated to make sound if one sets one's mind to it.
I'm thinking of your noisy arc comment. My experiences are limited but I think the most typical reason is that they are usually intermittent. Rather than a continuous arc, they are individual ones with negative resistance dropping the source voltage below the ionization level then stopping until it's exceed again. I've made arc lamps using projector carbons and they weren't very noisy, just a moderate frying sound. I was running them from AC and so don't know how they would have sounded with DC.
Somehow I think I'm going to stick with film or dome tweeters, and not Be ones at that. I don't like the idea of things that can easily burn the house down or contain toxic substances if it's avoidable. Even if they don't escape in normal usage they create a permanent waste-stream problem. But the concept of a wood-burning speaker is definitely fun. Excuse me, I've gotta go stoke the sound.
Rick
The ones I have heard from Acapella and Lansche Audio are quiet when there is no signal and as they are horn loaded there would be ample opportunity for them to be audibly noisy!
Truly the best highs I have heard...or not heard as you only notice how relaxed and effortless the highs are.
For a Chemist who thinks that an combing, acoustically large panel ES has good treble, a crackling ozone generator might just sound great :-).
The things that generate "good" sounds when audiophiles see how cool they look...
cheers,
AJ
This post will last approximately 2 minutes. 120,119,118,117...
That whole panel has less moving mass than your so called tweeeter. Add to the fact that high frequencies are only excited in a narrow band and beaming isn't a real issue either.
Electrostatic panels and make superb high frequencies with very low distortion, this is a fact. Now if you want to talk about dispersion this is another issue so please don't get the points confused.
That whole panel has less moving mass than your so called tweeeter.
Who mentioned mass? What so called tweeter? You don't understand the term acoustically large do you? Think diaphragm size vs wavelength.
Add to the fact that high frequencies are only excited in a narrow band and beaming isn't a real issue either.
Say what?
Electrostatic panels and make superb high frequencies with very low distortion, this is a fact.
Umm, ok. Because you say so? Or because you have measured the distortion of your panels? If so, can you post them? Might be understandable, given the radiating surface and required displacement.
Now if you want to talk about dispersion
We best not.
this is another issue so please don't get the points confused.
Thanks for clarifying everything for me :-).
cheers,
AJ
This post will last approximately 2 minutes. 120,119,118,117...
"You don't understand the term acoustically large do you? Think diaphragm size vs wavelength"
I know exactly what you are talking about and this is why I pointed out that MY electrostats narrow the radiating area with increasing frequency thus keeping dispersion relatively even.
"Umm, ok. Because you say so? Or because you have measured the distortion of your panels? If so, can you post them?"
I have measured the distortion but no I won't post it just to satisfy you. Its not my job to educate you.
"Might be understandable, given the radiating surface and required displacement.
"
Surface area is extremely large and needed excursion is small. Add to that symmetrical drive evenly over the whole surface and FLAT panels (none of this curved panel nonsense which just makes distortion) and you have very low distortion.
"We best not"
Why not? I told you my in-room FR and it is clear I have no serious dispersion issues despite the large panel size because of the cleverness of the design. Care to mention your speakers in-room response??
I know exactly what you are talking about
No, you clearly don't.
this is why I pointed out that MY electrostats narrow the radiating area with increasing frequency thus keeping dispersion relatively even.
Really? How? How does the single, coherent membrane do this?
Let me guess, you had polar data, but were destroyed in a chemical spill (or were smoked perhaps)?
I have measured the distortion but no I won't post it just to satisfy you. Its not my job to educate you.
Either that or you are lying. It's a typical reaction when a delusional person is called out about their hallucinations.
I told you my in-room FR and it is clear I have no serious dispersion issues despite the large panel size because of the cleverness of the design.
Your "in-room FR" at a single point makes it "clear I have no serious dispersion issues"? Thank goodness your chosen profession is chemistry.
Stick with it.
Care to mention your speakers in-room response??
To draw attention away from the falsified claims about your panels?
cheers,
AJ
This post will last approximately 2 minutes. 120,119,118,117...
"Really? How? How does the single, coherent membrane do this?"
Well if you would bother to read what I write you would know that it is done electrically through the stators, which are individually insulated wires and not a metal sheet like Martin Logan. This means that signal can be distributed differently at different parts of the stator. Getting any clearer? Honestly this information is out in the public domain so educating you on it is not my top priority. It is a pity that you know so little about the history of speaker design. Heres a hint; go to audiocircuit and look under electrostatic speakers and then Acoustat. Then look at the spectra series information.
"Either that or you are lying"
No, its my petulant reaction to your unending petulance.
"Your "in-room FR" at a single point makes it "clear I have no serious dispersion issues"? Thank goodness your chosen profession is chemistry.
Stick with it"
I guess its good that you are not a scientific person at all or I would write something nasty. You are simply too ignorant to understand what an in-room measurement says about dispersion.
"To draw attention away from the falsified claims about your panels?
"
No falsified claims just measureable proof of smooth flat frequency response in-room at 3.5 meters distance.
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