this is just one of those "food for thought" postings. I have an idea and I have not tried it out so have no hard proof as to will it or won't it work but I can see no reason why this would not be a very interesting experiment. So if you try this and it works just give me credit for the idea and if it does not work just forget i ever mentioned it.
The Maggie is a very popular speaker and those who love it do so with a passion. Maggies are in fact high mass drivers and their dirve system is extreemly non linear (read never ever linear). That said they can and do sound very wonderful. So we have compared to an esl which is very very linear and low distortion ultra low mass a speaker that generates a ton of second order harmonic distortion. This pretty much amounts to the difference between a high % distortion tube amp and an ultra low distortion SS amp. People fall in love with lots of second harmonic distortion.
So I suggest that some one build up a flat ESL panel with different thickness stator spacers. I should think that if there was a difference in thickness of about 25% front Vs back stator spacers that should generate some second harmonic distotion and sweeten thins up so the ESL does not sound so sterile. Then you can also play the game of front side Vs back side listening as they will both be different (with maggies some folks prefer one way to the other). That it so if anybody tries this idea please let me know what you find out.
The Maggie is a very popular speaker and those who love it do so with a passion. Maggies are in fact high mass drivers and their dirve system is extreemly non linear (read never ever linear). That said they can and do sound very wonderful. So we have compared to an esl which is very very linear and low distortion ultra low mass a speaker that generates a ton of second order harmonic distortion. This pretty much amounts to the difference between a high % distortion tube amp and an ultra low distortion SS amp. People fall in love with lots of second harmonic distortion.
So I suggest that some one build up a flat ESL panel with different thickness stator spacers. I should think that if there was a difference in thickness of about 25% front Vs back stator spacers that should generate some second harmonic distotion and sweeten thins up so the ESL does not sound so sterile. Then you can also play the game of front side Vs back side listening as they will both be different (with maggies some folks prefer one way to the other). That it so if anybody tries this idea please let me know what you find out.
JB: no not OT at all that was the point. ESL's and planar magnetics seem to share the same issues as tube amps and SS amps. The ESL (on paper) is light years ahead of any Planar magnetic loudspeaker. But just look at the huge body of died in the wool maggie users. I admit that the first time I heard a paie od SMGa's running on a Linn and all ARC electronics I was prepared to be very unimpressed and instead I was very impressed. In the same way that I was impressed by a tiny SE 3.4 watt amp (with bags of even order distortion). This hobby is not about right and wrong it is about the illusion of real music the emotion of music. Its kind of like we have been saying that HIFi speakers are better than PA speakers but it is not the case. The two are different that all they do different jobs. I have come across amplifier circuits that were intended to generate some extra even order distortion for just this very purpose. So why not sweeten up a set of ESL's a little and pump the illusion of the sound some?
Hello Morray!
Maybe that is even true when you compare the Maggies with "better" planar magnetics. I had the chance to listen to Magnepan and Analysis Audio speakers at the Highend in Munich this year and last year. I didn´t stay in the Analysis Audio room long enough last year, but this year I had the impression that the Analysis speakers are a class of their own in terms of dynamics (my recommendation for drum solos), but tonally a bit on the synthetic side compared to the Magnepans. I know I listened to the Maggies with Jeff Rowland electronics, while not having looked at the electronics in the Analysis room very carefully, but I think it was nothing well-known. A maggie critic at audioasylum (things exist between heaven and earth) told me it must have been the electronics.
About the asymmetric ESL: I played a bit with FEMM and the only way I see is building stators with different geometries and conductors on the diaphragms like in a magnetic planar to use the local non-linearities. My math teacher would have said: You can also drill a hole in your knee and fill it with jam. Why not get some nicely colored strong power amp? The Electrocompaniet NEMO is very nicely colored, I never heard their smaller ones.
regards,
Oliver
Maybe that is even true when you compare the Maggies with "better" planar magnetics. I had the chance to listen to Magnepan and Analysis Audio speakers at the Highend in Munich this year and last year. I didn´t stay in the Analysis Audio room long enough last year, but this year I had the impression that the Analysis speakers are a class of their own in terms of dynamics (my recommendation for drum solos), but tonally a bit on the synthetic side compared to the Magnepans. I know I listened to the Maggies with Jeff Rowland electronics, while not having looked at the electronics in the Analysis room very carefully, but I think it was nothing well-known. A maggie critic at audioasylum (things exist between heaven and earth) told me it must have been the electronics.
About the asymmetric ESL: I played a bit with FEMM and the only way I see is building stators with different geometries and conductors on the diaphragms like in a magnetic planar to use the local non-linearities. My math teacher would have said: You can also drill a hole in your knee and fill it with jam. Why not get some nicely colored strong power amp? The Electrocompaniet NEMO is very nicely colored, I never heard their smaller ones.
regards,
Oliver
Hello Morray!
As far as I know FEMM only allows defining lines as conductors, not blocks (I am currently using it for designing a magnetostatic speaker, not for electrostatic problems). A third outer stator with the voltage of the adjacent/opposite stator, as well as a dielectric on one side give only very slight non-linearities.
BTW, what I find boring about ESLs is mainly the transients and the poor integration with a dynamic bass. I would like to listen to a magnetic planar (not a muddy maggie) with ESL midrange.
Regards,
Oliver
As far as I know FEMM only allows defining lines as conductors, not blocks (I am currently using it for designing a magnetostatic speaker, not for electrostatic problems). A third outer stator with the voltage of the adjacent/opposite stator, as well as a dielectric on one side give only very slight non-linearities.
BTW, what I find boring about ESLs is mainly the transients and the poor integration with a dynamic bass. I would like to listen to a magnetic planar (not a muddy maggie) with ESL midrange.
Regards,
Oliver
Perhaps I'm missing something, but I don't see how having different front-stator-to-diaphragm and rear-stator-to-diaphragm distances would introduce second harmonic distortion into an ESL's operation. The electric field strength experienced by the diaphragm should be independent of the diaphragm's position between the two stators. The electric potential varies with position, but the field strength does not. (The electric field lines between two ~infinite plates are parallel.) If that weren't true the ESL would not be capable of the low distortion output pointed out in the original post.
Second harmonic distortion can be a problem in a curved ESL panel because the forces associated with forward and backward motion of the diaphragm are not symmetric: diaphragm motion in one direction stretches the diaphragm while motion in the other direction reduces its tension. With a flat, two-stator ESL, though, the second harmonic distortion should be low no matter what you do with the diaphragm-stator distances.
Few
Second harmonic distortion can be a problem in a curved ESL panel because the forces associated with forward and backward motion of the diaphragm are not symmetric: diaphragm motion in one direction stretches the diaphragm while motion in the other direction reduces its tension. With a flat, two-stator ESL, though, the second harmonic distortion should be low no matter what you do with the diaphragm-stator distances.
Few
An unbalanced drive will generate distortion...
as long as the diaphragm to stator spacing is balanced (identical) from one side of the speaker to the other then regardless of where in between the two stators the diaphragm is the combined forces pushing and pulling will always be the same. If you make one set of stator spacers thicker or thinner than the other side then the drive is off balance.
With curver ESL's yes you have some differing tensions forward to backward but for the most part you have tension in the length of the diaphragm which keeps it centred. Don't forget that you also have different front to back stator thicknesses. This is to accomodate large excursions where horizontal tensions will increase and so pull the diaphragm more flat thus drawing it closer to the rear stator. Push pull is low distortion because things are balanced and symmetrical. Skew the symmetry and the distortion goes up.
as long as the diaphragm to stator spacing is balanced (identical) from one side of the speaker to the other then regardless of where in between the two stators the diaphragm is the combined forces pushing and pulling will always be the same. If you make one set of stator spacers thicker or thinner than the other side then the drive is off balance.
With curver ESL's yes you have some differing tensions forward to backward but for the most part you have tension in the length of the diaphragm which keeps it centred. Don't forget that you also have different front to back stator thicknesses. This is to accomodate large excursions where horizontal tensions will increase and so pull the diaphragm more flat thus drawing it closer to the rear stator. Push pull is low distortion because things are balanced and symmetrical. Skew the symmetry and the distortion goes up.
That is my point....
having balanced push and pull force is as far as I know subject to having the two stators equal distance from the diaphragm (at rest). So if the system is symmetrical then the drive force is always equal regardless of where in between the two stators the diaphragm is positioned. As soon as the system balance is skewed it all falls apart.
having balanced push and pull force is as far as I know subject to having the two stators equal distance from the diaphragm (at rest). So if the system is symmetrical then the drive force is always equal regardless of where in between the two stators the diaphragm is positioned. As soon as the system balance is skewed it all falls apart.
The simple electrostatic model - a charge situated within a parallel plate capacitor would suggest that the force is independant of the charge's proximity to either plate.
I think to add distortion via electrostatic design, one would have to engineer a design wich incorporated a non-zero electric field gradient between the stators. in this way, field strength and hence driving force would vary with diaphragm displacement.
Ed
I think to add distortion via electrostatic design, one would have to engineer a design wich incorporated a non-zero electric field gradient between the stators. in this way, field strength and hence driving force would vary with diaphragm displacement.
Ed
Thanks for joining in Ed...
can you provide the english Coles Notes defination of this statement? "a non-zero electric field gradient between the stators"
Seems very logical to me that if you move away from a force be it magnetic or electroststic the affect of that force is diminished. So if you shift one stator farther away from the diaphragm than the other stator you have reduced the force of that stator on the diaphragn with respect to the closer stator. The combined balanced pushing and pulling force is lost. My understanding is that the two parallel stator plates must be equally spaced from the diaphragm at rest to make this trick work. Thanks Moray James.
can you provide the english Coles Notes defination of this statement? "a non-zero electric field gradient between the stators"
Seems very logical to me that if you move away from a force be it magnetic or electroststic the affect of that force is diminished. So if you shift one stator farther away from the diaphragm than the other stator you have reduced the force of that stator on the diaphragn with respect to the closer stator. The combined balanced pushing and pulling force is lost. My understanding is that the two parallel stator plates must be equally spaced from the diaphragm at rest to make this trick work. Thanks Moray James.
OK I'll try... The old physics is a bit rusty though 
Simple case. A paralel plate capacitor, i.e. our two stators separated by distance d. Say there is a peak in the music signal at some instant in time, and the stators have a potentlial difference V between them. If they are parallel, an electric field E =V/d, extends between them and is uniform. Thus a point charge Q placed within this field experiences a force F=QE. Since the field is uniform, the force does not depend upon the position of charge Q. i.e. in this case, you can't move away from the force.
Ed
Simple case. A paralel plate capacitor, i.e. our two stators separated by distance d. Say there is a peak in the music signal at some instant in time, and the stators have a potentlial difference V between them. If they are parallel, an electric field E =V/d, extends between them and is uniform. Thus a point charge Q placed within this field experiences a force F=QE. Since the field is uniform, the force does not depend upon the position of charge Q. i.e. in this case, you can't move away from the force.
Ed
I'll tack this on to the end of Ed's response:
The electric field is a "vector field." At each point in space we can define the electric field's magnitude and direction. Here's an example taken from Wikepedia:
It shows the electric field surrounding a positive charge (red) in the neighborhood of a negative charge (cyan). The blue arrows indicate the direction and magnitude of the electric field at many points in space (the locations of the arrows' tails). At a given location a positively charged particle would feel a force in the direction indicated by the arrow and the magnitude of the force would be proportional to the arrow's length. Since in this example the arrows have different lengths and directions, the electric field is not uniform. Ed's gradient (I think, strictly speaking, it ought to be the Jacobian since the electric field is a vector field) measures how the electric field changes from one location to its neighboring locations. If the gradient (Jacobian) at some point "A" is large then the electric field's magnitude and/or direction at some of the points surrounding "A" must be quite different from the electric at "A". In the example above the Jacobian would have large magnitudes near the charges because that's where the electric field changes most rapidly.
The electric field between two infinite parallel plates (ESL stators) would be indicated by an array of arrows all pointing in the same direction (from positive stator to negative stator), and all with the same length (proportional to the voltage difference between the stators). In other words, the electric field is uniform. Since all points have identical electric field magnitudes and directions, the Jacobian is zero at all points. Since the arrows are all identical, and they indicate the force felt by a positively charged particle at the various points in space, we see that a charged particle placed anywhere between the plates feels the same force as it would at any other place between the plates.
Moray James, if it troubles you that the force does not vary with distance, consider that as you move farther from one stator you move closer to the other, by exactly the same amount.
Or, if that doesn't help try an audio example. The SPL from a point source of sound drops off as 1/distance^2. It drops off as 1/distance as you move away from an infinitely long linear source. It doesn't drop off at all as you move away from an infinitely large planar source.
I hope I haven't just further muddied the waters...
The electric field is a "vector field." At each point in space we can define the electric field's magnitude and direction. Here's an example taken from Wikepedia:
It shows the electric field surrounding a positive charge (red) in the neighborhood of a negative charge (cyan). The blue arrows indicate the direction and magnitude of the electric field at many points in space (the locations of the arrows' tails). At a given location a positively charged particle would feel a force in the direction indicated by the arrow and the magnitude of the force would be proportional to the arrow's length. Since in this example the arrows have different lengths and directions, the electric field is not uniform. Ed's gradient (I think, strictly speaking, it ought to be the Jacobian since the electric field is a vector field) measures how the electric field changes from one location to its neighboring locations. If the gradient (Jacobian) at some point "A" is large then the electric field's magnitude and/or direction at some of the points surrounding "A" must be quite different from the electric at "A". In the example above the Jacobian would have large magnitudes near the charges because that's where the electric field changes most rapidly.
The electric field between two infinite parallel plates (ESL stators) would be indicated by an array of arrows all pointing in the same direction (from positive stator to negative stator), and all with the same length (proportional to the voltage difference between the stators). In other words, the electric field is uniform. Since all points have identical electric field magnitudes and directions, the Jacobian is zero at all points. Since the arrows are all identical, and they indicate the force felt by a positively charged particle at the various points in space, we see that a charged particle placed anywhere between the plates feels the same force as it would at any other place between the plates.
Moray James, if it troubles you that the force does not vary with distance, consider that as you move farther from one stator you move closer to the other, by exactly the same amount.
Or, if that doesn't help try an audio example. The SPL from a point source of sound drops off as 1/distance^2. It drops off as 1/distance as you move away from an infinitely long linear source. It doesn't drop off at all as you move away from an infinitely large planar source.
I hope I haven't just further muddied the waters...
Thanks, Few.
Yes, what I meant by gradient should really be termed divergance, to use accepted definitions.
The electric field between parallel stators has zero divergance, but is established by a potential gradient (the difference in voltage between the electrodes).
To create a field divergance, it would be necessary to devise some non planar stator electrode geometry. I envisage all sorts of technical difficulties with this...
Of course another way to introduce distortion would be to add a little music signal to the diaphragm, thus changing the charge level (I know about the high surface resistivity etc...)
Ed
Yes, what I meant by gradient should really be termed divergance, to use accepted definitions.
The electric field between parallel stators has zero divergance, but is established by a potential gradient (the difference in voltage between the electrodes).
To create a field divergance, it would be necessary to devise some non planar stator electrode geometry. I envisage all sorts of technical difficulties with this...
Of course another way to introduce distortion would be to add a little music signal to the diaphragm, thus changing the charge level (I know about the high surface resistivity etc...)
Ed
You are right... and I was wrong...
I cannot find anything that would support my belief that the stators have to be equally spaced from the diaphragm for the force vectors to always add up the same. I asked a buddy who knows better than I and he told me the same. I still have to imagine that at some distance things stop working the same way but I have no idea how much different the stator spacers could be and still have things equal out. I made the assumption a long time ago and just ran with it. Live and learn.
So what would be an easy way to introduce some second order harmonic distortion short of a single ended esl?
I cannot find anything that would support my belief that the stators have to be equally spaced from the diaphragm for the force vectors to always add up the same. I asked a buddy who knows better than I and he told me the same. I still have to imagine that at some distance things stop working the same way but I have no idea how much different the stator spacers could be and still have things equal out. I made the assumption a long time ago and just ran with it. Live and learn.
So what would be an easy way to introduce some second order harmonic distortion short of a single ended esl?
As I mentioned in my previous post - addition of some music signal to the diaphragm would achieve this.
This would modulate the static charge (achieved by the DC bias). Say the diaphragm is biased at some positive DC voltage + 10% music. On positive portions of the waveform, bias is increased, hence diaphragm driving force is increased. The reverse is true on negative going portions of the music signal.
It is simple to show that this would in theory add a perfectly controllable amount of 2nd harmonic distortion.
The problem would be in actually delivering music signal to the diaphragm, as the sheet resistivity is usually high to restrict charge flow on the surface...
Ed
This would modulate the static charge (achieved by the DC bias). Say the diaphragm is biased at some positive DC voltage + 10% music. On positive portions of the waveform, bias is increased, hence diaphragm driving force is increased. The reverse is true on negative going portions of the music signal.
It is simple to show that this would in theory add a perfectly controllable amount of 2nd harmonic distortion.
The problem would be in actually delivering music signal to the diaphragm, as the sheet resistivity is usually high to restrict charge flow on the surface...
Ed
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