Yup, my direct-driver amp was half-way between Brian Beck's glorious monster and a Sanders. Absolutely the way to go for a DIYer (if they have no children in the home) but not feasible for folks who sell ESLs (should be obvious who seems cool to the notion).
A lot of this discussion is over my head (and some comments are not coherent) but here are a few points which I believe to be true.
The spacing of the ESL parts is a mechanical choice driven, ideally, by the excursion you want which in turn is acoustic/mechanical at root. As spacing goes up, voltage requirements go up fast. But you want to be able to have high bias voltage which requires big spacing.
The bias voltage dramatically (square power?) increases the sensitivity of the speaker - a very good goal (good to have adjustable bias so you can crank it up in dry weather). Prolly also influences linearity - but a long time since I read the famous foundational book by Hunt, the guy from MIT. Bias voltage depends on spacing and air humidity.
We are talking about electrostatic forces (duh). You need hundreds of voltage of push-pull to traverse even millimeters of space to move the diaphragm with electrostatic forces.
So, aim for bigger spacing, very high bias (easy to make), and good signal voltage.
A lot of this discussion is over my head (and some comments are not coherent) but here are a few points which I believe to be true.
The spacing of the ESL parts is a mechanical choice driven, ideally, by the excursion you want which in turn is acoustic/mechanical at root. As spacing goes up, voltage requirements go up fast. But you want to be able to have high bias voltage which requires big spacing.
The bias voltage dramatically (square power?) increases the sensitivity of the speaker - a very good goal (good to have adjustable bias so you can crank it up in dry weather). Prolly also influences linearity - but a long time since I read the famous foundational book by Hunt, the guy from MIT. Bias voltage depends on spacing and air humidity.
We are talking about electrostatic forces (duh). You need hundreds of voltage of push-pull to traverse even millimeters of space to move the diaphragm with electrostatic forces.
So, aim for bigger spacing, very high bias (easy to make), and good signal voltage.
Hi,
Besides every microphone positioned in near field prooves the matter.
Microphone.. how old fashioned
Why not try the ESL simulator and set the speaker-mic to 1cm.
Actually I'm interested in how regular headphones (not electrostatic ones) behave.
If they have linear response when voltage driven, does that mean that they will have a non-linear one when current driven ?
Does that mean that a headphone amp for regular headphones cannot be a current drive ?
Voltage vs. current drive of dynamic speakers has been discussed at great length several times on this site (albeit in a different subforum). Insofar as consensus was reached, I think the gist of it can be summarized as follows:
"Since dynamic speakers are designed to be driven by voltage sources, it is suboptimal to use them with current sources. Current drive works very well but only when the speaker was specifically designed for this mode of operation. In other words, you need to design the entire system for current drive"
and
"If current drive were really superior to voltage drive, we would have more current drive speaker/amp systems out there in the market."
Kenneth
"Since dynamic speakers are designed to be driven by voltage sources, it is suboptimal to use them with current sources. Current drive works very well but only when the speaker was specifically designed for this mode of operation. In other words, you need to design the entire system for current drive"
and
"If current drive were really superior to voltage drive, we would have more current drive speaker/amp systems out there in the market."
Kenneth
Hi,
a dynamic speaker or headphone behaves differently with current-drive. Basically the voltage drive curve is overlayed with the impedance plot.
This means that the voltage-driven response curve is a bit elevated where the impedance plot rises and lowered where the impedance plot is lowered.
Damping of the driver is omitted with. So especially at the resonance point Fs the driver´s response peaks. Current drive makes sense when You want to implement motional feedback because it easens the FB loop design.
Otherwise there´s typically nothing really gained from current-drive...the same as it is with ESLs.
Ben, Your assumption that an increase of d/s is positive is wrong.
It is correct that the polarizing Voltage Vpol should be as high as possible, close to the limiting flashover level of air, since the Force acting upon the membrane rises with rising Vpol. But how do other parameters influence the Force, like membrane Area and the d/s?
The Force acting on the diaphragm consists of two parts, a static part and a dynamic part.
The static part simply leads to an offset x of the diaphragm from its middle position between the stators. We all know the effect from seeing the membrane flex when the polarizing voltage is switched on.
The dynamic part of the Force is the one that moves the membrane after the music signal.
Both parts add up independantely, because the superposition principle applies here.
After P.Baxandall the Force calculates to:
F= Eps0*A*[2*Vpol²*x/d³ + Vpol*Vsig/d²] with Eps0=8.854exp-12, A=diaphragm area, Vpol=polarzing Voltage, Vsig=signal Voltage, d=d/s-value and x=Offset of the diaphragm from its middle position.
We can rearrange the above equation in that Vpol/d is substituted by Epol, the polarizing field strength and a constant in this calculation, which is limited by the flashover level of air of approx. 2kV/mm
The formula then reads:
F=Eps0*A*[2*x*Epol²*(1/d) + Vsig*Epol*(1/d)] introducing the constant M=Eps0*A and the variables N=2*x*Epol² and P=Vsig*Epol, the formula reads easier.
F=M*[N*(1/d) + P*(1/d)]
This shows the 1/d-relationship of the Force in both, the static as well as the dynamic part.
So one should not aim for bigger spacing but just the opposite!
When designing a panel one needs to specify the dynamic range and the lower bandwidth limit. From this set of values one can estimate which volume of air is needed to fulfill the requirement.
This leads to a set of area-values A and excursion-values d. One should always choose the largest area allowed or possible and the smallest d. This increases the Force acting upon the diaphragm the most.
It is not that You choose a value of polarising Voltage first and adjust d accordingly, but quite the opposite. A chosen d-value allows for a certain maximum Vpol.
Besides the voltage levels quickly becoming unpractical and more dangerous to handle with rising d-values, the power requirements also rise proportional to d².
Since we are free in the design of the panel shape and since it is easy to design larger membrane areas than with comparably sized dynamic drivers the option should always be: "larger in A, smaller in d"
jauu
Calvin
a dynamic speaker or headphone behaves differently with current-drive. Basically the voltage drive curve is overlayed with the impedance plot.
This means that the voltage-driven response curve is a bit elevated where the impedance plot rises and lowered where the impedance plot is lowered.
Damping of the driver is omitted with. So especially at the resonance point Fs the driver´s response peaks. Current drive makes sense when You want to implement motional feedback because it easens the FB loop design.
Otherwise there´s typically nothing really gained from current-drive...the same as it is with ESLs.
Ben, Your assumption that an increase of d/s is positive is wrong.
It is correct that the polarizing Voltage Vpol should be as high as possible, close to the limiting flashover level of air, since the Force acting upon the membrane rises with rising Vpol. But how do other parameters influence the Force, like membrane Area and the d/s?
The Force acting on the diaphragm consists of two parts, a static part and a dynamic part.
The static part simply leads to an offset x of the diaphragm from its middle position between the stators. We all know the effect from seeing the membrane flex when the polarizing voltage is switched on.
The dynamic part of the Force is the one that moves the membrane after the music signal.
Both parts add up independantely, because the superposition principle applies here.
After P.Baxandall the Force calculates to:
F= Eps0*A*[2*Vpol²*x/d³ + Vpol*Vsig/d²] with Eps0=8.854exp-12, A=diaphragm area, Vpol=polarzing Voltage, Vsig=signal Voltage, d=d/s-value and x=Offset of the diaphragm from its middle position.
We can rearrange the above equation in that Vpol/d is substituted by Epol, the polarizing field strength and a constant in this calculation, which is limited by the flashover level of air of approx. 2kV/mm
The formula then reads:
F=Eps0*A*[2*x*Epol²*(1/d) + Vsig*Epol*(1/d)] introducing the constant M=Eps0*A and the variables N=2*x*Epol² and P=Vsig*Epol, the formula reads easier.
F=M*[N*(1/d) + P*(1/d)]
This shows the 1/d-relationship of the Force in both, the static as well as the dynamic part.
So one should not aim for bigger spacing but just the opposite!
When designing a panel one needs to specify the dynamic range and the lower bandwidth limit. From this set of values one can estimate which volume of air is needed to fulfill the requirement.
This leads to a set of area-values A and excursion-values d. One should always choose the largest area allowed or possible and the smallest d. This increases the Force acting upon the diaphragm the most.
It is not that You choose a value of polarising Voltage first and adjust d accordingly, but quite the opposite. A chosen d-value allows for a certain maximum Vpol.
Besides the voltage levels quickly becoming unpractical and more dangerous to handle with rising d-values, the power requirements also rise proportional to d².
Since we are free in the design of the panel shape and since it is easy to design larger membrane areas than with comparably sized dynamic drivers the option should always be: "larger in A, smaller in d"
jauu
Calvin
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Hello Calvin,
I agree that for practical reasons it is desirable to use large A with smaller d.
However, the “static” + “dynamic” force formula you rearranged does not support the conclusion that smaller spacing results in larger obtainable forces on the diaphragm. The spacing, d , is not actually involved in defining the obtainable force per unit area. Only the flashover field strength of air is involved.
Starting from your intermediate step where you had substituted Epol for Vpol/d:
F=Eps0*A*[2*x*Epol²*(1/d) + Vsig*Epol*(1/d)]
Looking at just the “dynamic” portion of the Force:
F = Eps0*A*Vsig*Epol*(1/d)
Substituting Esig for Vsig/d and solving for Force per unit area gives….
F/A = Eps0*Epol*Esig
So, the Force per unit area is proportional to the product of the Signal field strength and the Polarizing field strength. The spacing, d, only defines the signal voltage and polarizing voltage required to reach a given field strength . For the practical reason of minimizing the transformer step-up ratio it is desirable to select the minimum spacing required to handle the diaphragm excursions at the lower bandwidth limit.
Said another way:
For ESLs, maxSPL is NOT dependent on diaphragm to stator spacing, although the required Vsig & Vpol required to achieve it increase linearly with D/S. Note that this does not mean that you can use whatever spacing you want to go as low as you want. The spacing still must be defined to allow the required diaphragm motion for maxSPL at the LF breakpoint.
Looking at just the “static” portion of the Force:
F = Eps0*A*2*x*Epol²*(1/d)
Solving for Force per unit area and rearranging gives….
F/A = 2*Eps0*Epol²*(x/d) = (constant)*(x/d)
This is the linear negative stiffness term that results in a force proportional to the diaphragm displacement in the gap away from the central resting position x=0. For a given spacing, d, the larger the polarizing voltage, the larger the negative stiffness coefficent and the lower the fundamental resonance of the diaphragm.
See this thread for plots of resonance trends vs Vpol I posted before I had read the Baxandall paper.
http://www.diyaudio.com/forums/planars-exotics/147801-diaphragm-resonance-change-hv-bias.html
Since this thread is about current drive, I will add that Baxandall mentions in Section 3.3.2 that if the stators are fed from a current source the linear negative stiffness term drops out of the Force equation. This means that varying the polarizing voltage would have no affect on the fundamental resonance of a current source driven ESL. I haven’t verified this experimentally yet, but plan to in the near future.
Concerning Vpol selection:
It is true that for a given Vsig, increasing Vpol will increase the force on the diaphragm and increase the voltage sensitivity of the ESL. However, this does not neccessarily produce the maximum possible Force on the diaphragm and thus the maximum possible SPL peaks. From Section 3.2.9 of the Baxandall paper, for a given diaphragm spacing d, the optimum Vpol and Vsig(stator-stator) for maximum SPL are:
Vbias = Emax * d / 2
V(stator-stator) = Vbias * 2
where Emax = the flashover voltage for air usually taken to be 2kV/mm - 4kV/mm.
The reasons this is so is because the force is proportional to the product of the two voltages, but the break down is based on the sum of the two voltages. For example, suppose the airgap can sustain 10kV, and Force(for illustrative purposes) is just the product of the Vpol and Vstator.
Vpol...Vstator..Force
0........10.........0
1.........9.........9
2.........8........16
3.........7........21
4.........6........24
5.........5........25
6.........4........24
7.........3........21
8.........2........16
9.........1.........9
10........0.........0
You can see that if we are limited by 10kV across the airgap, we get maximum force(peak SPL) before breakdown in the airgap when we set Vpol= 5kV and apply 5kV of audio signal to each stator.(out of phase of course, so Vsig=10kV from stator to stator) This is consistant with the Baxandall equations.
In practice what you will find is that:
1) If your step up transformer can generate the optimum stator voltages, turning up your bias beyond the optimum Vpol value will result in higher sensitivity but reduce maximum SPL.
2) If your transformer generates less than optimum stator voltages, turning up your bias beyond the optimum Vpol value will result in higher sensitivity and increased maximum SPL.
Thanks for that in-depth treatment.
"2)"... right. Like Mike Wright said.
Seems to me there's not much doubt that big spacing and proportionally smaller diaphragm movement leads to cleaner results. A loafing big cone driver will outperform a stressed small driver and likewise for an ESL for similar reasons.
Calvin - while your math looked superficially impressive (at least until I read bolserst incisive critique), it would be far more helpful (or to use the current cliche, "inclusive") if you could put into plain language words what you are doing, finding, and concluding. Then the rest of us could judge what made sense and what didn't and how it relates to Hunt.
About current vs voltage, I've fooled some with motional feedback for cones and that is a matter of juggling positive and negative and voltage and current sourcing. In order to create an amp with a negative output impedance equal to the driver (no kidding). The dirty little secret (at least with cones) is that it is all a matter of balance between cone diameter and the radiation resistance of the air and some other acoustic parameters and there just isn't a "right" way to drive. By convention (and because of the need/convenience for negative voltage feedback around amps), the audio world universally agrees to market the kind of speakers that sound kind of flat in kind of ordinary homes and room when driven with constant voltage drive. By convention. Secondarily, you need various tricky and changing EQ with current drive and Rice-Kellogg drivers.
"2)"... right. Like Mike Wright said.
Seems to me there's not much doubt that big spacing and proportionally smaller diaphragm movement leads to cleaner results. A loafing big cone driver will outperform a stressed small driver and likewise for an ESL for similar reasons.
Calvin - while your math looked superficially impressive (at least until I read bolserst incisive critique), it would be far more helpful (or to use the current cliche, "inclusive") if you could put into plain language words what you are doing, finding, and concluding. Then the rest of us could judge what made sense and what didn't and how it relates to Hunt.
About current vs voltage, I've fooled some with motional feedback for cones and that is a matter of juggling positive and negative and voltage and current sourcing. In order to create an amp with a negative output impedance equal to the driver (no kidding). The dirty little secret (at least with cones) is that it is all a matter of balance between cone diameter and the radiation resistance of the air and some other acoustic parameters and there just isn't a "right" way to drive. By convention (and because of the need/convenience for negative voltage feedback around amps), the audio world universally agrees to market the kind of speakers that sound kind of flat in kind of ordinary homes and room when driven with constant voltage drive. By convention. Secondarily, you need various tricky and changing EQ with current drive and Rice-Kellogg drivers.
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If it were a simple matter to generate large signal voltages I might agree, but this is not the case. You have to think of the ESL as a system made of either (panel + transformer) or (panel + DD amplifier). In either case, you will find the quality and bandwith of the audio signal decreases as you attempt to increase the magnitude of the signal voltage with a higher step-up ratio transformer or higher voltage DD amplifier.
In short, I agree with Calvin's advice to use only as as large a gap as you need to.
This minimizes the magnitude of the required signal voltage which maximizes fidelity.
Unlike cone drivers, ESLs are capable of low distortion reproduction all the way to their excursion limits. I haven't found the concept of "loafing" to be applicable to ESLs.
Did you think I meant you should go to the lumber yard and buy the biggest spacers you can find?
I meant you figure out how big you can go within your capability, humidity level in your home, amp/transformer resources, etc. But, I think you start somewhat like with cones, with some notion of how low in frequency you want to go and work from there. I don't offer that thumbnail sketch as a prescription, just a rough from-the-hip shot at the kind of system thinking is part of initial planning.
Yes, aim for big spacing just like I think you should always aim for large woofers.
Weird special case: Mike Wright encased his speakers in sealed mylar. Then filled with inert gas. So right off (if you want to go to all this trouble and play through myler "grill cloth") you can jack up the bias voltage (easy to do) and have real sensitivity. An interesting place to start?
I meant you figure out how big you can go within your capability, humidity level in your home, amp/transformer resources, etc. But, I think you start somewhat like with cones, with some notion of how low in frequency you want to go and work from there. I don't offer that thumbnail sketch as a prescription, just a rough from-the-hip shot at the kind of system thinking is part of initial planning.
Yes, aim for big spacing just like I think you should always aim for large woofers.
Weird special case: Mike Wright encased his speakers in sealed mylar. Then filled with inert gas. So right off (if you want to go to all this trouble and play through myler "grill cloth") you can jack up the bias voltage (easy to do) and have real sensitivity. An interesting place to start?
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Hello Bentoronto,
What I understood you to say was that with an ESL panel of a given area and a given maximum diaphragm displacement you would prefer to use larger spacing since this would mean the diaphragm would be moving a smaller percentage of the total D/S airgap. That is what I thought you meant by ”proportionally smaller diaphragm movement”. Is this what you meant?
Just curious, wouldn't aiming for large ESL area be more comparable to aiming for large woofers? I keeping thinking that somehow I am not understanding what you are meaning by aim for big spacing.
Based on Baxandall analysis and my limited experience, you should aim for the largest area you can live with because the area is the only physical parameter other than the breakdown voltage for air that defines maximum SPL capability of an ESL panel. The D/S spacing merely defines how low in frequency you can output that maximum SPL.
Hi,
The formulas clearly show a anti-proportionality of attainable Forces to the distance d. It also shows that You need to increase the voltages to obtain the same Force-values when You increase d.
Since we must(!) stay below the maximum force which is defined by the flashover treshold, only the range below Fmax is of interest and here the 1/d proportionality applies. In other words. As long as the panel doesn´t flashover a decrease in spacing d will result in higher Force, hence higher SPL, if we keep Vpol and Vsig unaltered. On the other hand, if we increase d we need to increase Vpol and Vsig to rearrange for the same Force again. The choice of d should then only depend on the excursion needs. So, if we have chosen a value for d that meets the excursion demands, any further increase in d is not only obsolete, but actually counter productive, in that the required higher voltages (and associated with it increased Power) mean increased effort, inferior signal quality, less safety and speeded aging.
If I were to design a F1 car, I surely wouldn´t opt for a 125ccm Motorbike engine, but a 3.000ccm racing engine. Why
when You can 
?
A tranny that is incabable of supplying the optimal Vsig is simply not the right tranny for that certain application.
jauu
Calvin
That is just a part of the truth.
The formulas clearly show a anti-proportionality of attainable Forces to the distance d. It also shows that You need to increase the voltages to obtain the same Force-values when You increase d.
Since we must(!) stay below the maximum force which is defined by the flashover treshold, only the range below Fmax is of interest and here the 1/d proportionality applies. In other words. As long as the panel doesn´t flashover a decrease in spacing d will result in higher Force, hence higher SPL, if we keep Vpol and Vsig unaltered. On the other hand, if we increase d we need to increase Vpol and Vsig to rearrange for the same Force again. The choice of d should then only depend on the excursion needs. So, if we have chosen a value for d that meets the excursion demands, any further increase in d is not only obsolete, but actually counter productive, in that the required higher voltages (and associated with it increased Power) mean increased effort, inferior signal quality, less safety and speeded aging.
Turning the Vpol up will result in flashover as soon as the Vsig approaches the peak-value.
This is indeed correct, but who would design so in first place?
If I were to design a F1 car, I surely wouldn´t opt for a 125ccm Motorbike engine, but a 3.000ccm racing engine. Why
when You can ?A tranny that is incabable of supplying the optimal Vsig is simply not the right tranny for that certain application.
In comparison and similarity to dynamic drivers the superiority of the larger driver stems from its lower excursion needs. Increasing spacer thickness (which is how I interprete "big spacing" here) beyond what is needed to fulfill the dynamics requirements gains nothing and improves nothing.
jauu
Calvin
Bolserst - your questions indicate you are paying my rambling amateur thoughts more respect than they deserve. Thank you.
From my rambling thoughts, I would select "system" and "initial" as useful concepts. A person is sitting in their armchair thinking, "How to start....?" Their variables are things like what kind of mechanically stable panels can they make at home and, inter-relatedly, what kind of voltages for bias and drive. How big and wide? (Adding depth is, of course, very easy.) How high are the voltages that are practical for them?
I'd say hard to keep panels adequately stiff, especially as the surface dimensions grow. So there are hard limits a builder faces unless they can weld steel braces. But it is not too hard to increment voltages upwards with bigger spacing, if you have a solid mechanical base. With the high voltages around ESLs, I bet few people are rapping their knuckles on the panels or feeling them for vibration while playing - that's the way we always do it with speaker boxes. Ever wonder how badly the flimsy Quad panels rattle? Or sheets of perforated steel that everybody uses? You could trust your life to the strength of Dayton-Wright panels, by contrast. Why are we nutty about the solidity of speaker boxes but pay minimum attention to the rigidity of ESL panels?
Yes, going big in any dimension means proportionally and absolutely less diaphragm displacement - but easier to achieve with spacing. Which, I am pretty sure, means better performance. The mathematics of ESL forces are not pretty, as best as I can remember Hunt. That's why big-voltage bias HAD to be introduced, eh. I think as soon as you start serious movement, you get into exponential instead of linear forces.
From my rambling thoughts, I would select "system" and "initial" as useful concepts. A person is sitting in their armchair thinking, "How to start....?" Their variables are things like what kind of mechanically stable panels can they make at home and, inter-relatedly, what kind of voltages for bias and drive. How big and wide? (Adding depth is, of course, very easy.) How high are the voltages that are practical for them?
I'd say hard to keep panels adequately stiff, especially as the surface dimensions grow. So there are hard limits a builder faces unless they can weld steel braces. But it is not too hard to increment voltages upwards with bigger spacing, if you have a solid mechanical base. With the high voltages around ESLs, I bet few people are rapping their knuckles on the panels or feeling them for vibration while playing - that's the way we always do it with speaker boxes. Ever wonder how badly the flimsy Quad panels rattle? Or sheets of perforated steel that everybody uses? You could trust your life to the strength of Dayton-Wright panels, by contrast. Why are we nutty about the solidity of speaker boxes but pay minimum attention to the rigidity of ESL panels?
Yes, going big in any dimension means proportionally and absolutely less diaphragm displacement - but easier to achieve with spacing. Which, I am pretty sure, means better performance. The mathematics of ESL forces are not pretty, as best as I can remember Hunt. That's why big-voltage bias HAD to be introduced, eh. I think as soon as you start serious movement, you get into exponential instead of linear forces.
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I notice in this thread and others talk of the danger of the bias voltage. I understand this with regard to DD tube amps. Indeed you do not want to screw with that "spark" from a the likes of a Acoustat Servo amp. I might be wrong about that though. I have zapped myself many times however with the 5KV DC of a Acoustat Mk121 interface box. I have also touched a naked panel all over its surface and even poked a finger into the styrene grid and never received a shock. The fact is I regularly pull bare panels off the interface boxes and discharge them and have even touched the 5KV terminal by accident in the power supply and while it is damned unpleasant I can't vouch for "deadly" by any stretch. What am I missing with regard to this topic. Sorry to high jack the thread. I encourage the original discussion to commence promptly. Great stuff guys.
This comment is well informed!
The power supply in most electrostats charges to between 2 and 5 kv. That sounds like alot, and it is. So the natural questions is - can you fry youself? No you can't. There is not enough current available to create the internal burns that electrocution causes. Does that mean that working with electrostats is safe? No. This high voltage, despite the low current, can stop your heart, as your heart depends on the progression of electrical signals to coordinate timing - a fact that defibrillators exploit. In audiospeak, "fibrillation" is when different parts of the heart go out of phase. The defibrillator snaps them back, so that the timing re-aligns.
Where this is dangerous is when the high voltage hits a finger on one hand, and the ground hits a finger on the other - and you get high voltage acting across your chest. THIS CAN KILL YOU. The solution is to wear rubber gloves, or to keep one hand in your pocket while poking around. This is a fact that was confirmed by the inventor of the curved elecrostatic speaker, who also happens to be a medical doctor (Roger Sanders).
The power supply in most electrostats charges to between 2 and 5 kv. That sounds like alot, and it is. So the natural questions is - can you fry youself? No you can't. There is not enough current available to create the internal burns that electrocution causes. Does that mean that working with electrostats is safe? No. This high voltage, despite the low current, can stop your heart, as your heart depends on the progression of electrical signals to coordinate timing - a fact that defibrillators exploit. In audiospeak, "fibrillation" is when different parts of the heart go out of phase. The defibrillator snaps them back, so that the timing re-aligns.
Where this is dangerous is when the high voltage hits a finger on one hand, and the ground hits a finger on the other - and you get high voltage acting across your chest. THIS CAN KILL YOU. The solution is to wear rubber gloves, or to keep one hand in your pocket while poking around. This is a fact that was confirmed by the inventor of the curved elecrostatic speaker, who also happens to be a medical doctor (Roger Sanders).
Hi,
Walker´s and Baxandall´s calculations just provide for that.....estimation of the SPL against driving current. You just need to calculate the current values, depending on frequency, the panel´s impedance and the driving voltage. But as You can see from the Walker-equation-simulator, the results just give a hint about the range of possible results. Too many factors affect the end result. Factors like the shape of the panel, the use manufacture and type of insulation, building precision, diaphragm coating, transformer, etc. etc.
jauu
Calvin
ps. the curved Stator was ´invented´ before Sanders. And also way before ML adopted this technique, claiming it their intellectual property under the name "curvelinear stator". There´s at least one patent dated from 1957 (Austria) and one from 1961 (USA) and I really doubt that the applicants were the first who thought about curved stators. Most of all techniques were invented in the early days already. There are no really big News in ESL-tec since the 1960s.
Walker´s and Baxandall´s calculations just provide for that.....estimation of the SPL against driving current. You just need to calculate the current values, depending on frequency, the panel´s impedance and the driving voltage. But as You can see from the Walker-equation-simulator, the results just give a hint about the range of possible results. Too many factors affect the end result. Factors like the shape of the panel, the use manufacture and type of insulation, building precision, diaphragm coating, transformer, etc. etc.
jauu
Calvin
ps. the curved Stator was ´invented´ before Sanders. And also way before ML adopted this technique, claiming it their intellectual property under the name "curvelinear stator". There´s at least one patent dated from 1957 (Austria) and one from 1961 (USA) and I really doubt that the applicants were the first who thought about curved stators. Most of all techniques were invented in the early days already. There are no really big News in ESL-tec since the 1960s.
Call me a dullard but I just don't see it?
I'm trying to fit it all togeather but the physics is getting a little dense for me.
Wave popagation and energy transport wasn't really covered all that well in high school physics.
Is there an other equation by Walker and Baxandall that I have missed?
I'm trying to fit it all togeather but the physics is getting a little dense for me.
Wave popagation and energy transport wasn't really covered all that well in high school physics.
Is there an other equation by Walker and Baxandall that I have missed?
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