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Old 15th January 2013, 06:39 AM   #11
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You must also remember that when using power toroids in reverse for ESL that you must limit the lowest frequency operation per volts input as well to avoid saturation of the core causing distortions of the signal and extreme overloads to the amplifier.

This is a very simple rule as most ESL setups are of a hybrid design and goes as follows,

Being that the transformers are designed for 60HZ (or some that are for 50Hz as well) you can't put more voltage in to any winding than what it is rated for at 60hz.
otherwise you will saturate the core.
This goes for primary and secondary winding's alike.

No more than 240v into the 240v winding ( or two 120v's in series) and no more than 6Vrms into the 6v winding at 60Hz or 50hz for some.

But you ask " Then how do I put 60Vrms into the 6v winding and get 2400Vrms out of the 240v winding?".

Here is why,

If you double the frequency going into the winding of the transformer then you can double the voltage across the winding as well without saturating the transformer's core.

Therefore in order to be able to input 12Vrms into the 6V winding you must make sure that the frequency of the signal that goes into the winding must not be less than 120Hz.
Then you can safely input 12v into the 6v winding without cuasing any core saturation issues and this will double your output voltage on the 240V winding to 480vrms as well.

Then 24v at no less than 240HZ as well and so on.

This is a linear function of reciprocals so for 30Vin/6V for the winding =5, 5 * (the winding frequency of) 60hz = 300hz.
So for your average amplifier of 100watts (28Vrms) you must never let any frequency's lower than 300Hz enter into the transformers 6V winding at a 30V level.

The same goes for the above example of 60Vrms into the 6V windng and that frequency of course would 600Hz.

That is how we get away with using these types of transformers as a woofer covers the lower frequency's below that point of cutoff.

Read through this thread,

Step-up transformer design

It will help you to have a better idea of how this technique works as I go through the analysis of one of my cores that I had purchased a bunch of for cheap.
It also goes well into the theory and the hows and why's as well as many other factors besides the transformation ratio in how to make them work properly.

I found out as well that they work pretty good if one chooses not to want to wind from scratch.

I also show how to add your own custom primary winding to change to a custom transformation ratio following the same rules I just described.
It may be possible to get by with a single core instead of two per panel using this technique.
I have done this but there are limitations and the reasons are explained in the thread and I will explore this more in my next article.

I am working on a newer up too date article using the Antec AS-1206 power transformer for ESL's.

It won't be as confusing and will be more straight forward then that last thread because I was still learning myself at the time.
Also I had run into a few issues in testing that I had since worked out.
I will try to explain what those issues are again in the new article as I have described them on occasion in other threads.

Cheers !!

Jer

Last edited by geraldfryjr; 15th January 2013 at 06:57 AM.
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Old 15th January 2013, 10:38 AM   #12
sreten is offline sreten  United Kingdom
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Hi,

Yes for a constant charge push pull the diaphragm is charged
and the signal in antiphase across the stators, hence push pull.

Voltage depends on the spacing, the original Quads are
1.5KV for the treble panel and 6KV for the bass panels.

rgds, sreten.
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Old 21st January 2013, 10:39 AM   #13
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Here is a neat little chart that I found somewhere that can give you an idea of the voltages involed in powering an ESL as per D/S and amp power size.

It doesn't take into account for panel size or added transformer capacitance as it is just a generalization of typical parameters.

Enjoy!!

jer
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Old 22nd January 2013, 04:18 PM   #14
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Quote:
Originally Posted by geraldfryjr View Post
Here is a neat little chart that I found somewhere that can give you an idea of the voltages involed in powering an ESL as per D/S and amp power size.
The chart was posted here:
Current vs voltage drive ESL?


It was created based on Section 3.2.9 of Baxandall's chapter on ESLs where he derives values for Vbias and Vstator to maximize ESL output.
What limits the efficiency of ESLs is the the breakdown voltage for air. Emax is a function of D/S spacing and stator smoothness.
He used a value of Emax=4kV/mm for calculations on the QUAD ESLs.

For a given diaphragm spacing d, the optimum Vbias and V(stator-stator) are:
Vbias = Emax x d / 2
V(stator-stator) = Vbias x 2

For example, an ESL with 2mm spacing between diaphragm and stator you will maximize peak SPL with:
Vbias = 4000 V
V(stator-stator) = 8000 V

If you plan to use a 100Watt amplifier(28.3Vrms = 80Vpp) you will need a transformer with a step-up ratio of 100:1 to achieve the maximum possible SPL.Using a larger step up ratio will not increase the peak SPL, it will only allow you to achieve the peak SPL with a lower voltage from your amplifier. Trying to increase the stator voltage beyond 8000V with 4000V bias will result in the air conducting(arcing-hissing) and not an increased SPL. If your maximum stator voltages are <8000V then you can increase output and sensitivity by dialing up your bias voltage.

The way to make ESLs louder is to increase the area. Equations for required Area given a desired SPL is covered in Section 3.3.9


Here is the reference.
P. J. Baxandall, “Electrostatic Loudspeakers,” in
Loudspeaker and Headphone Handbook, J. Borwick, Ed.
(Reed Educational and Professional Pub., Woburn, MA,
1998), pp. 106–195.
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Old 22nd January 2013, 07:03 PM   #15
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Thanks Boserst!!!

I had found it while I was sorting through some files and I had no label on it.
I figured it was based along the lines you describe.

I have ran bias voltages as high as +10kv and transformation ratios as high as 1: 200 to 400.
This greatly increased the sensitivity to where a 10v to 20v p-p input was more than enough to make may little panel to get very loud at +106db at 1meter ( and about nearly 110db at .5meter).

I can't even imagine what a larger panel is going to be like,But I will soon.

I have found that getting voltages above 8kv proves to be very difficult to contain although not impossible.
I have a new build that should sustain these voltages better than the last one.

My last panels with a diaphragm size of 3.25" X 9.75", I had pushed them to ionization of the air in the gap and they were so loud that I couldn't notice any distortions caused by the ionizing.

What was nice was that it took less than 4V p-p to have a comfortably loud SPL for normal listening using my smaller 80watt cheapy amp.
Suitable for maybe a small class A amp of some sort and still provide plenty of SPL's for enjoyment.

Getting a woofer ( not to mention a small one) to keep up is the new challenge!!!

Cheers !!

jer

Last edited by geraldfryjr; 22nd January 2013 at 07:09 PM.
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Old 28th September 2013, 08:39 PM   #16
galop is offline galop  Slovenia
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Hello.I was order and plug to panels 2x 2x110v 2x6v 50VA toroids and with fullrange signal and highest levels have alot of distorsion.If i understand if i want to plug amplifier with 30v pp transformer will be around 2x30v 2x300v for full range?So if i want drive full range panels what to tell transformer manufacturer?Regards

Last edited by galop; 28th September 2013 at 08:55 PM.
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Old 29th September 2013, 09:52 AM   #17
Calvin is offline Calvin  Germany
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Hi,

it has been stated quite repeatedly -lastly in #3 of this thread(!)- that the standard power toroids are not useably for fullrange-ESL useage.
They are designed for efficient useage of their core material and wire at the power line frequency, hence 50Hz or 60Hz. To allow for higher input voltage the signal frequency must be raised.
Also, the summed resistances of amp and transformer combined with the inductance of the transformer defines the lower bandwidth limit.
A lower bandwidth limit requires a higher inductance.
This in turn requires more windings, which in turn requires a larger core.
Larger panels with higher capacitance require larger cores.
I suggest at least 50VA for a 1nF panel @>300Hz. 80VA seems optimal.
A 2nF panel may be driven by 120VA core toroids from >150Hz on.
Iīd like to point out that I donīt recommend the useage of toroids with dual primaries and dual secondaries, but single prim/single sec instead.
It was an experiment by Charlie which went ok with the trannies he chose, simply because he couldnīt source 230V/6V toroids easily.
While the flashover treshold of single windings trannies is clearly defined/specified and sufficently high (4kVrms and more), the multiple windings toroids flashover treshold between the two secondaries(!) may be as low as 500Vrms.
Another point to keep in mind regards the transformation factor.
Mostly the transformer is viewed as a voltage/voltage and current/current converter. But its also - and I dare to say even more so, due to the quadratic relationship- a impedance converter.
Its of low reward to only calculate voltage or current relationships if the impedance values donīt blend. Standard amplifiers are optimized to drive load impedances between 4 and 8 Ohms and depending on their stability within a phase angle range of ~+-45° (with a certain tolerance for lower and higher values). The transformer is now asked to transform the very high valued and very high phase-angled impedance of the panel to a lower and amp-acceptable range of values.
Beeing closer to ideal than other transformers, toroids present the amlifier more of the īreactiveīnature of the panel, i.e. the phase angle the amplifier has to cope with may reach very high values, close to the theoretical 90°.
Itīs this phase angle that many amplifiers canīt cope with, not the low impedance at the upper bandwidth limit (where the phase tends to 0° again), as it may drive the amp into a ringing step response and even oscillation.
So take a moment and think about Your amps capablities with regard to stability into reactive loads.

Fortunately it seems, that if certain basic design parameters -namely efficiency of the panel- are chosen correctly, most other important design values fall into the right place like in a mechanical watch, at least for non-segmented metal-sheet panels. Segmented wire stators typically require higher transformation factors (>1:100) which would ask for 2x2 secondary lowvoltage windings with standard power trannies.
Afaik nobody has reported about such a setup yet.
I only tested wire stators positive with arrays of simple EI 230/6V trannies, but that could be a hint that the toroids will work in this application also.

jauu
Calvin
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Old 29th September 2013, 09:21 PM   #18
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Quote:
Originally Posted by galop View Post
So if i want drive full range panels what to tell transformer manufacturer?Regards
Are you asking what specifications to give a transformer manufacturer for them to build you a custom transformer for full range operation of your ESLs? If so the starting point, as Calvin mentions, is to define what power amplifier you will be using, and what the impedance of the ESL panel is. How big is it? What is its capacitance, is it segmented?
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Old 30th September 2013, 02:16 AM   #19
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Hi I have a industrial transformer, it steps down from 6000v to 120v, would it be useable on an esl ? curious
Al
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Old 30th September 2013, 09:32 AM   #20
galop is offline galop  Slovenia
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I didnt do measurements yet.Will be 2 panels per channnel size 100cm x 25cm with perforated metal.
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