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Old 1st April 2010, 03:24 PM   #171
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thanks Calvin for the reply ,I feel alot better now.
yes I see that you are very busy with alot of different things as i have been doing alot searching and reading of earlier posts and threads trying to figure out if i have done somehing wrong or if i am asking too much (using such a small panel) that the laws of physics will allow.
I too was shocked when I had realized the quadstack setup was 480:1 and greater depending on the number of primary turns chosen.
However it did give me the best effeciantcy.
due to my measuring disabilities at the moment i cannot investagate this any further until a later time.
So, my question is that ,at which piont does the drive voltage become too much for a given bias voltage to yeild any more output for given panel and what is the maximum percentage of diagphram movement allowable within a given d/s spacing before the possibilty of discharging the diagphram from being too close to the stator.
I'm sure frequency has alot to do with this.
I have a variable bias supply and can set it to a maxium voltage that the panel will allow wihtout acring.
for instance was able to maintain a 40volt p-p sine with a 1:480 (19,200volt p-p) ratio with a bais voltage (I'm guessing )around 5kv with a d/s of .0625" and it was extremely loud with a sinewave of 300 hz and up.
Any more voltage demand than this especialy above 10 khz the amp could not deliver the current and distort and do funny things until it finaly over loaded and shutdown.
This proved to be true when playing music and sharp peaks would occur and shutdown the amp.
This was also the case with lower ratios, as i stated in a earlier post.
No where in my research has anybody stated what it takes (or tried) to reach their maximum limits and only some simple guide lines of how to get one working.
However there has been a few that has attemped such a feat and gave up easily.
I just happen to be one that doesn't give up very easily.
When one says that you shouldn't do it this way but I do anyway and find it gives me better results than the old way.
I then start asking questions and want to know why it is not supposed to work ,when it does.
sorry,for being so long winded. jer
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Old 1st April 2010, 04:08 PM   #172
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Please be careful with these voltages, they are deadly!
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Old 1st April 2010, 04:18 PM   #173
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Default Vbias and Vstator for maximum ESL output

Quote:
Originally Posted by geraldfryjr View Post
No where in my research has anybody stated what it takes (or tried) to reach their maximum limits
If you haven't read it already, Section 3.2.9 of Baxandall's chapter on ESLs derives values for Vbias and Vstator to maximize ESL output.
What limits the efficiency of ESLs is the the breakdown voltage for air. He uses a value of Emax=4kV/mm for dry air.

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 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.

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 1st April 2010, 04:31 PM   #174
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Quote:
Originally Posted by geraldfryjr View Post
I too was shocked when I had realized the quadstack setup was 480:1 and greater depending on the number of primary turns chosen.
How did you measure this 480:1 step up ratio?
The only way to get this ratio is if each of your 4 transformers have individual 10 turn primaries and they are all wired in parallel.

From your pictures you are wrapping 10 turns of wire through all 4 toriods at once. When you do this you create 4 parallel paths for the flux, one in each of the cores. Since only 1/4 of the total flux travels in each core, you effectively divide the turn ratio for each transformer by the number of cores you have inside the 10 turn primary.

For one of your transformers with the secondaries in series and a 10 turn primary you get 120:1 step up ratio.

If you stack two of your transformers and put a 10 turn primary around both cores, you will get 60:1 step up from the primary to each of the transformer series connected secondaries. Putting both sets of transformer secondaries in series and you will get 120:1. Same as for a single transformer, but you now have the 10 turns wound around twice the core area so your saturation capability is doubled.

With a quad stack and 10 turn primary around all four cores, your total step-up with all secondaries in series should still be 120:1. But your saturation capability is now quadrupled.

Last edited by bolserst; 1st April 2010 at 04:45 PM.
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Old 1st April 2010, 05:28 PM   #175
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thank you jonas, I am well aware of the dangers involved when working with high power high voltages.
I have many years working with high power tube rf amplifiers and television H.V. circuitry.
My worst experience ever was when I accidentally touched one leg of a 4 foot jacobs ladder powered by a large 15kv neon transformer ten years ago.
How I survived that one is beyond me,luckily it didn't render me unconscious.
Becuase I lived 23 miles from nowhere and lived by myself at the time.
So please don't worry.
And I thank you very very much for your concern. jer
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Old 1st April 2010, 06:48 PM   #176
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Thanks Steve,as it is all becoming very clear to me now.
Do remember reading that(post #173) and have a copy of Baxandals papers some were in my archives.
Having the bias set close to the edge would result in breakdown on some single tone test.
So then i would just back it down slightly until it went away.
That puts alot of light on the subject.
The 1:480 ratio was a straight foward asumption calculation.
I was getting ready to start reading up on magnetic circuits again and figured this being the case of why I was only able to calculate a 1:130 ratio on the quad stack.
I think that in all of my different combination test it was the 1:120 ratio in both single, double stack and dual single stack that gave me the best results in dynamic range except for low frequency handling which was understood due to core size.
This is when I realized that my amp isn't going to cut it in the final configuration although it allows me to just listen to them.
I had the same problem 7 years ago when I first powered them up using using some 6v6 pp output transformers and this same amp.
And if I remember correctley,when I took them back to florida to my friends place were we had the studio,I hooked them up to an alesis RA100 amplifier and it was the best I had ever heard them sound at that time ,even with the crappy transformers!
So,with that being said these transformers made a big big world of difference.
I don't have any decent amps running at the moment as two are still in florida powering the appogge dueta's ,one got stolen from my garage last summer and the other a bgw that has a bad channel and my two sunn concert slave amp need a go'in over also.
I guess I've got some repairing to do!
Or I have five lm4780's laying around doing nothing but sitting on my bench.
I thinking 4 opamps in a parallel or bpa configuration just might due the trick and get me by for now until I get my bigger panels and transformers made.
Anyway, How does this all figure into the variable transformation ratio of 1:130 to 1:160 I was measuring at one frequency by varying the voltage level only?
As always yours and everone elses thoughts and opinions are welcome.

jer

Last edited by geraldfryjr; 1st April 2010 at 06:52 PM.
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Old 1st April 2010, 07:00 PM   #177
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Also,I forgot to mention,This must be the reason why I would get that nasty little pulse a above 20volts peak. jer
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Old 2nd April 2010, 01:59 AM   #178
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Quote:
Originally Posted by geraldfryjr View Post
Anyway, How does this all figure into the variable transformation ratio of 1:130 to 1:160 I was measuring at one frequency by varying the voltage level only?
jer
In case you missed my comments on this topic buried in the middle of post # 158
Step-up transformer design


>>>>>>>>>>

I'm not sure the cause of your turns ratio discrepancies without more information.

1) What frequency were you doing the measurements? To avoid contaminating your measurements with the resonant interaction of leakage inductance and winding capacitance I'd recommend using a low frequency of 100 to 500 Hz. If you use a frequency near the resonant frequency mentioned above and are not using a series damping resistor you can measure an "effective" turns ratio of 2 to 3 times that at low frequencies. This is the cause of the SPL peak seen at the top end of the audio band on most ESLs. You need to choose a damping resistor to tailor the response to your liking. You will see increasing values of "effective" turns ratio as you approach the resonance. At the frequency of maximum peaking, you will measure the minimum impedance, and the maximum current drawn from your amplifier. Just below this frequency is where many amplifiers have stability issues as the impedance is still quite low, and the phase can be -60 deg or more.

2) Were you using a series resistor? If yes: Were you measuring the input voltage for the ratio calculation before or after the series resistor. You should measure after the resistor, directly across the primary winding.

3) Were you watching the waveform on the oscilloscope to make sure that distortion or clipping would not affect the voltage reading of your meter?

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Old 2nd April 2010, 04:01 AM   #179
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I tried all kinds of different freqeuncy's.
Freqeuncy did seem to affect the effect.
Although I didn't check to see if the amount the effect was affected by the frequency.
Follow me ?
If not will try to explain in a different way.
Yes I was using a sereis resistor of 10 ohms.
My setup up was as follows:
10 ohm resistor in series with 10 turn primary on the ground side.
Scope directly connected the output of the amplifier(input to the circuit) to make sure the input voltage was maintained contstant as the frequency was changed and to make sure I had a nondistorted sine wave.
One volt meter across the resistor and a second seperate voltmeter across the primary winding.
So, I could monitor all three at the same time.
I"m not sure if it was the quadstack or ,one single core as to get a baseline figure.
I'm thinking that both exibited the same effect.
so, I started to do a compleate set of measurements.
After realizing that I wrote one of the results in a wrong place,I back tracked to properly record the result.
While doing this discoverd that the two 120v windings were connected in series and disconneceted them.
This changed the results I had already recorded.
I then decided that I would make a new chart to included the second set of parameters,later.
So,with this problem still rolling around in my head.
I tuned to a frequency were the voltages across the winding and the resistor were equal and checked to see if the variable ratio effect still exsisted and it did.
Thats when I realized I had even more different sets of parameters to contend with.
So, I said to myself okay it is late I'm tired and I'll deal with that tommorrow as this would give me time to replan a new chart.
Meanwhile ,lets back track and check a few things.
It was at this piont the meters were not being very cooperative as the battery's were getting pretty low and needed to be changed out.
Just as I had this third one measuring the 120v winding it was acting squirrely and died just as I was turning up the voltage.
The pulse appeared on the scope and fried the meter.
The next day, I found some new battery's and it just got worse.
As I have already explained.
So now here I am meterless.
Somedays you just have to laugh!
Reguardless of the circumstance or circumstances.
Thats how that went.
I hope that I answered your questions,okay.
I can always duplicate some parts of the process but not the ones were the meters burned because they are already done!(ha ha ha, oh boy)
What I ment was I can still go back and duplicate a certain setup for some measurement in question. jer

Last edited by geraldfryjr; 2nd April 2010 at 04:07 AM.
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Old 2nd April 2010, 02:44 PM   #180
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Quote:
Originally Posted by geraldfryjr View Post
Perhaps I don't understand the ratio that you are talking about. The setup you describe, measuring voltage across primary and series resistor, is a measurement setup for impedance not step-up ratio. You would need to measure the voltage at your series connected secondary windings to get step-up ratio.

1) Impedance does change with input voltage magnitude and frequency as I've mentioned before.
2) Impedance does change depending how you have your secondary windings connected as this is changing how the winding capacitance is loading the transformer.
3) Changing impedance will change the ratio of the voltages measured across the series resistor and the transformer primary.
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