A question about ozone coming from ESLs came up in another thread and I wanted to crowd-source thoughts about it. A quick search here wasn't helpful.
I know ozone is truly dangerous when strong - destroys your lungs not to mention rubber and other stuff. But you can smell it it in concentrations 10% of the OSHA harmful level.
The once popular high voltage ion generators and electrostatic cleaners have lost their appeal (partly because of cheap HEPA-like filters being available).
Of course, that after-thunderstorm ozone smell is viewed as a nice. And ozone does have use as a disinfectant and water purifier.
If you smell some ozone, are you ESL panels doing something wrong or is that normal?
My 2-cents.
Ben
I know ozone is truly dangerous when strong - destroys your lungs not to mention rubber and other stuff. But you can smell it it in concentrations 10% of the OSHA harmful level.
The once popular high voltage ion generators and electrostatic cleaners have lost their appeal (partly because of cheap HEPA-like filters being available).
Of course, that after-thunderstorm ozone smell is viewed as a nice. And ozone does have use as a disinfectant and water purifier.
If you smell some ozone, are you ESL panels doing something wrong or is that normal?
My 2-cents.
Ben
ESLs should NOT be generating ozone. Ozone is bad for you and the health of your ESL coatings and insulators.
If they generate ozone even when not playing music the bias voltage is set too high for the air gap size and stator construction type, or there is a leakage path.
Generally ozone production is accompanied by soft blue glow of corona visible in total darkness after waiting 15 minutes for your eyes to adjust. Alternatively, you can use a microphone/amplifier/headphones setup to listen for the tell tale wooshing sound of corona discharge.
Thanks.
Ozone is not produced unless there is voltage discharge? There are no discharges except when you blow moist breath at the ESL panel? No random discharges?
Here's a scary article on ozone from EPA:
Ozone Generators that are Sold as Air Cleaners | Indoor Air | US Environmental Protection Agency
Ben
Ozone is not produced unless there is voltage discharge? There are no discharges except when you blow moist breath at the ESL panel? No random discharges?
Here's a scary article on ozone from EPA:
Ozone Generators that are Sold as Air Cleaners | Indoor Air | US Environmental Protection Agency
Ben
To the best of my knowledge, ozone is only generated when the voltage potential between diaphragm and stator is such that ionization in the airgap occurs and the air becomes conductive. It might be just slightly conductive, like when you blow moist air into the airgap and hear hissing. But, that is enough.
Often ionization only occurrs in the middle of the panel where the diaphragm is closer to one of the stators, or in a localized area where there are particularly sharp edges on the stators. In my experience, smooth wire stators are much less prone to ozone generation.
It can also be conduction through surface leakage paths along foam spacers or stator frames.
Often ionization only occurrs in the middle of the panel where the diaphragm is closer to one of the stators, or in a localized area where there are particularly sharp edges on the stators. In my experience, smooth wire stators are much less prone to ozone generation.
It can also be conduction through surface leakage paths along foam spacers or stator frames.
I'm not sure what comes first. But voltage flows through air when the voltage gradient is great enough to ionize the air molecules, esp. oxygen. That means it is making ozone. So there is no current flowing and no breakdown at lower voltages and no ozone?
But when you breathe moist air, the breakdown voltage becomes very low but I suppose it is still ionizing the molecules between the water droplets. So it is making a little bit of ozone.
I guess I am wondering if an ESL panel can be entirely free of ozone generation, even when mild bias voltage is used?
Ben
But when you breathe moist air, the breakdown voltage becomes very low but I suppose it is still ionizing the molecules between the water droplets. So it is making a little bit of ozone.
I guess I am wondering if an ESL panel can be entirely free of ozone generation, even when mild bias voltage is used?
Ben
I used to have a pair of Quad ESL 57 and never smelt ozone in the 15 years of ownership.. I believe that the QUAD used covers to prevent dust getting in which would also prevent ozone getting out. I never had any problem or took them apart so I can't confirm that though.
I would have thought that any ozone production is low though because the resistive coating was such that the bias had to be on for many minutes before the speakers worked properly.
I would have thought that any ozone production is low though because the resistive coating was such that the bias had to be on for many minutes before the speakers worked properly.
You either have broken/covered with dust isolator and patial:
http://upload.wikimedia.org/wikiped...eep.svg/461px-Corona_discharge_upkeep.svg.png
or barrier discharge:
http://upload.wikimedia.org/wikipedia/commons/thumb/e/e6/DBD.png/800px-DBD.png
The first one would occur without audio signal applied - old TV sets and computer monitors generate ozone due to HV leakage
The second one is due to displacement current, AC only (like the one through the capacitor).
Both types will erode whatever material nearby so it's quite easy to spot the bad spot (sorry, can't help it). Both will make things worse over time.
You need to identify the source and fix it: cleaning, resorting isolators etc.
As others mentioned before energize your speakers in absolute darkness. Take time to adapt your vision: it may be very dim.
With and without signal applied.
Barrier discharge is kinda pinkish and does produce unmistakable crackling sound, partial discharge is rather bluish and has it's own unmistakable whistling sound, very subtle.
In really bad cases one can get spark discharge - easiest to identify due to loudness.
Hope this help
P.S. I would check the web to see how these phenomenas look and sound if you have never seen it before...
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Wow, a hard question to answer with words. Doesn't seem to be an issue for others and you seem to be on the trail of it, so maybe that's the first answer. A clean, after the thunderstorm smell but not quite like chlorine... dunno. Most other "electrical" smells resemble burning stuff, eh.
As the thread OP says, you can smell it at concentrations FAR below the threshold deemed dangerous by our duly authorized authorities, at least last time I checked or had any reason to doubt their authority. That's a big problem: how can you judge when the concentration of ozone is getting close to 10X the level you first could detect it at????
Ben
There was some discussion in another thread that a lot of the smell we generally associate with ozone is actually due to negative ions(ie not harmful)
http://www.diyaudio.com/forums/planars-exotics/146008-esl-bias-supply-polarity.html#post1860525
http://www.diyaudio.com/forums/planars-exotics/146008-esl-bias-supply-polarity-3.html#post2223925
We used to use ozone detection cards back in the lab...had different sections of the card that would change colors at different concentration levels.
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