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Old 6th June 2009, 08:13 PM   #141
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Default Coating

Hi, Chinsettawong.

The distortion was probably due to other causes, many, well not so many, have used aluminized mylar with almost zero resistance
succesfully. The company Final for instance, uses a low resistance film with the stepped up signal connected to it. Beveridge Inc did exactly the same in the seventies with a three stator, two membrane driver. Aucostat Inc used aluminized film in early speakers.

And so on......

Regards, Jonas
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Old 6th June 2009, 11:45 PM   #142
Few is offline Few  United States
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But in the cases you've cited, Jonas, my understanding is that the stators had high resistance. The stators and diaphragm have just exchanged roles as far as resistivity is concerned. I believe either the stators or the diaphragm (not both) have to have high resistivity in order to ensure low distortion at low frequencies.
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Old 7th June 2009, 09:32 AM   #143
Calvin is offline Calvin  Germany
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Hi,

the distortion situation can be kept acceptably low if the stroke of the membrane can be kept small. So its a method which is quite usable for Midhigh-panels, but less so for Bass/FR-panels.
Finals ´inverted´technology has two advantages and these are easier and therefore cheaper construction and safety (still a very important one though). To have the lowcurrent- highvoltage bias on the stators means that in case the stator insulation breaks down, there will be no lethal potential. The possibly lethal potential on the membrane (highvoltage-highcurrent) is still ´encapsulated´ between the stators.
Signals are distorted with this constant voltage technology much more than with the constant charge technology. And time will tell how long this technology lasts. They wouldn´t be the first where the complete aluminized membrane burns down within seconds in a spectacular way.
The stators are of sheetmetal type, so no highimpedance values and constant or fixed charge here!

jauu
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Old 7th June 2009, 11:06 AM   #144
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When I think about a child playing with a metal object around an esl, I would prefer it beinig a conventional esl, not inverted. I really can't see any safety benefits in that inverted type.
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Old 7th June 2009, 12:34 PM   #145
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When I did the experiment on the low resistant diaphragm, I actually kept everything else the same and changed only the diaphragm. The distortion was very obvious.

Wachara C.
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Old 7th June 2009, 12:59 PM   #146
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Default Inverted system

Quote:
Originally posted by MJ Dijkstra
When I think about a child playing with a metal object around an esl, I would prefer it beinig a conventional esl, not inverted. I really can't see any safety benefits in that inverted type.
Hi MJ Dijkstra,

I second that!
It's lethal to have tensions of 3500v on plates that are not isolated like it should be. If I touch a panel of a leaking ESL I'll have shocks that follows the music.

Thus it's lethal for a child.


Just my 2 cents.

Best Regards,


Audiofanatic
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Old 8th June 2009, 07:39 AM   #147
Calvin is offline Calvin  Germany
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Hi,

the 3.5kV of bias should not lethal. You might get a slight shock, but it´s not harmful since there is not enough current flow possible. At least thats the way a bias supply schould be designed (remember its not the voltage that is dangerous but the current!)
So the dangerous part of the ESL is where the high voltage and high current meet, which are the Audio-tranny, the cabling to and from the stators and the stators (with a conventional ESL). With the inverted ESL its the Audio tranny, the cabling to the diaphragm and the diaphragm.
The conventional ESL is perfectly safe as long as the insulation barrier of the stators works. It becomes a potential danger, when the insulation breaks down. This is what I had in mind, when I said the inverting ESL would be safer. But as MJ correctly pointed out, the diaphragm of an inverted ESL carries the dangerous voltages/currents and since it can´t be isolated enough, every conducting object (pins, nails,etc) that reaches through the stator holes could provide for a massive, if not lethal shock. I wonder how Final managed to fulfil UL and other safety standard requirements.

jauu
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Old 8th June 2009, 09:06 AM   #148
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Default Lethal?

The Final speakers two bias supplies are fairly low impedance, otherwise you should end up with a low pass filter between
stator/film capacitance and bias supply. Thats why there is a 10nF cap parallelled at the bias output. I dont know if the 0.6 joule of energy stored in this cap its lethal....
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Old 9th June 2009, 01:14 PM   #149
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As a precaution to electrical shocks, what kind of guards or isolation materials do you put on the outside of the stators? As for my headphones, I use the same material as my diaphragm to put on the outside of stators. This not only prevents the possibility of electrical shock, it also protects the sweat. But what if it is a big ESL using painted, perforated metal sheet, what would you do to prevent?

Wachara C?
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Old 10th June 2009, 09:40 AM   #150
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Default Distortion

Wachara, the distortion you heard could be the fact that the metallized membrane has a kind of transient rich sound with more attack compared to a high ohm membrane. The later often,
I think, sound too soft. On the whole, the different sounds of various membrane materials is an unexploited field.....
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