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2.1 (Good) Sound System with Singing Arc

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Chip Fixes

Fri Apr 08 2011, 10:23PM

Registered Member #3781 Joined: Sat Mar 26 2011, 02:25AM
Location:
Posts: 701

I don't know where to start, but here goes. I built a plasma speaker with a 555 timer and it came out quite well. So I did some research and watched a lot of youtube videos and I have come to the conclusion that I could, and will, build a loud 2.1 loudspeaker with good (see post below for clarification) sound quality that encorporates a singing arc. Such as these do:
http://www.enjoythemusic.com/magazine/equipment/1002/acapellavoilin.htm
http://www.youtube.com/watch?v=F2n3uikCkQg&feature=related

Design:
I have some general ideas for the design, please feel free to add to them and to help me out!
For input power: I think 12v would be the easiest to run the circuits off of since 12v power supplys for miscellaneous electronics are very cheap.
I liked the LED strip lighting Trampro87 used in his video and I would like to do the same thing, except I would house the 'brains' of the operation in a wood case with a removable (plexiglass?) (top)?
I would like the 'Audio In' to be a 3.5mm headphone jack. I will add a headphone jack as well.
I would like a subwoofer output in the back with ~30 watts of power so it can run a small subwoofer but will still be able to be used as a preamp. It would also have an on/off switch and volume control (and an adjustable crossover frequency?). I suppose I should put in 2 midrange outputs as well unless the arcs are pretty big and are able to cover the lower frequencies.

Singing Arcs
There would be two seperate free-standing tweeters (with a midrange speaker attached below?) composed of an arc such as in the setup in the youtube video. (I would store the tansformer, driving the arc, directly below the tweeter, preferably out of sight). I would like to house the tweeters in something a little more classy then a plastic box. Such as a nice wood case with a plexiglass front so you are able to view the arc and maybe it could have a horn device attached to the top to further amplify the sound. I'm thinking the arcs would be driven by DC flyback drivers because they are cheap and easy to get. I found that an arc that went from point to hemispherical worked best. I would also really love to make it so the system can stay on but the arcs will cut out after a few minutes of not being in use, such as what Acapella does, (maybe it will only power on when there is electricity flowing through the 'Audio In'?)

The Circuit
I recieved a few FETs for free from Fairchild:
http://www.fairchildsemi.com/pf/FQ/FQP32N20C.html
http://www.fairchildsemi.com/pf/FQ/FQP17N40.html
http://www.fairchildsemi.com/pf/FD/FDP036N10A.html

Parts List
Deluxe IC Prototype PC Board - $3.75 ea. http://www.goldmine-elec-products.com/prodinfo.asp?number=G17129
(2) High Voltage Flyback Transformer - $4.00 ea. http://www.goldmine-elec-products.com/prodinfo.asp?number=G17744

Side Notes
There are conflicting sources that say the arcs produce a lot of ozone, if this is true, how much? and can it be filtered out?
I don't have a budget but cheaper is better as long as im not sacrificing anything that was stated above.
I will be updating this post so check back here every once in a while.
I plan to take detailed pictures/notes to post on Instructables and I will submit this to Popular Science when it is finished.

I apologize that I am not smart enough to figure out most of this by myself, as I am only 17 haha and I have never taken an electronics class (self taught) as they are not offered at my school :( but I do love to learn; I'm able to read schematics and I'm a fast learner. I hope to have this project completed within a year. You're help is very appreciated! Oh, i also have a LOT of electronics so I should not have to buy too many parts.

James

Fri Apr 08 2011, 10:40PM

Registered Member #3610 Joined: Thu Jan 13 2011, 03:29AM
Location: Seattle, WA
Posts: 506

Poke around on here, plenty of people are playing with this stuff.

The arcs do produce some ozone, I find that the higher the voltage you use, the more ozone.

Singing arcs are fun, but the sound quality is not great under the best of conditions. If you want a novelty then go for it, but if you want great sound, buy some cheap dome tweeters. Flybacks vary, but I get good hot arcs out of ones that came from old SVGA computer monitors and TV sets, especially larger ones.

Tightmopedman9

Sat Apr 09 2011, 02:51AM

Registered Member #3197 Joined: Tue Sept 14 2010, 04:56PM
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Posts: 19

Fundamental design flaw of the air-cored plasma speaker (such as tramppros) is that the core will saturate at a relatively low frequency, ~200kHz. Since you can't drive it above this frequency PWM will introduce some interpolation errors. Assuming 10kHz input and 200kHz driving frequency you should expect around -90db distortion.

Everything you outlined is aesthetic stuff, the easy stuff. There is lots of reading to be done on the internet, to build something well you'll have to be very familiar with all the components. Datasheets are you friends.

Ozone is not a noticeable problem, you should not be concerned unless you have it in a very small room for a very long time.

Chip Fixes

Sat Apr 09 2011, 03:34AM

Registered Member #3781 Joined: Sat Mar 26 2011, 02:25AM
Location:
Posts: 701

alright, thanks! what about wiring two flybacks in series to create a larger arc?

magnet18

Sat Apr 09 2011, 05:55PM

Registered Member #3766 Joined: Sun Mar 20 2011, 05:39AM
Location:

Posts: 624

I saw 3 things
1. If you use an AC flyback, there is no "point to hemisphere" It's AC
2. Most headphone jacks are designed so that when a jack is plugged it there is a contact that is broken, look at one sometime, you might be able to use this.
3. Make sure you do your homework with the ozone, the guy that invented the plasma speaker died of ozone poisoning, but it really depends on your arcs and the ventilation of the room.
You might consider a source of an inert gas such as argon which is heavier than air and doesn't create anything but argon when ionized, or helium which is lighter than air. If the room is calm a bowl of argon should last awhile before dissipating.

Chip Fixes

Sat Apr 09 2011, 07:29PM

Registered Member #3781 Joined: Sat Mar 26 2011, 02:25AM
Location:
Posts: 701

Ah yes, thanks for pointing that out, I changed it.

After some research i decided that I will use DC flybacks instead of AC.

Helium tanks tend to be quite big and must be refilled. What if I made the tweeter box a vacuum, wouldn't that stop the production of ozone? (the box would then have to be a sealed enclosure of course) I also found ozone filters but I believe they are for big factories so I am not sure how well they would work, I will look into it. Furthermore I found some cheap ozone meters which will report the amount of ozone in the air (the maximum amount established by OSHA is 0.08 ppm).

Also I think I should clarify the whole great sound quality I was talking about: It doesn't need to be audiophile good, or $23,500 good, I just need a set up that is loud enough to hear clearly from the other room without any crackling from the arc.

magnet18

Sat Apr 09 2011, 07:32PM

Registered Member #3766 Joined: Sun Mar 20 2011, 05:39AM
Location:

Posts: 624

Well, a vacuum would stop the ozone, but it's hard to have sound without something for it to travel through...

The filter is probably excessive, and ozone has a distinct odor, so you should be able to tell yes/no whether a significant amount is being created, but if the meter is cheap it might be a good idea.

Chip Fixes

Sat Apr 09 2011, 07:47PM

Registered Member #3781 Joined: Sat Mar 26 2011, 02:25AM
Location:
Posts: 701

Alright the ozone meter is out of the question, the cheapest one I could find was $100+
I have an air purifier that emits ozone and I can smell it even though it says it's a safe amount so if I am able to smell ozone off the arc it may not mean it's at a harmful level.

I updated the first post

James

Sun Apr 10 2011, 01:58AM

Registered Member #3610 Joined: Thu Jan 13 2011, 03:29AM
Location: Seattle, WA
Posts: 506

I don't think a bowl of Argon would last long. Even if the room air is completely still, the hot arc will create enough convection current to empty the bowl quickly.

I haven't found small amounts of ozone to be a problem, but then I don't normally have arcs running for hours at a time either.

Adam Munich

Sun Apr 10 2011, 02:29AM

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

Ozone is not much of a problem with high current low voltage arcs like a plasma speaker uses. I have not noticed any ozone at all from my speaker, even when I sit next to it for an hour.

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