Seen positively, you no longer seem to accuse me being possibly malicious "per se"
I often find people having trouble to switch points of perspective – not seldom even experts like you - to my constant surprise.
What I bring into the discussion is not really what already is carved in stone (being wrong from time to time isn't really a shame IMO) but rather a way of approaching problems not yet solved in an multidisciplinary manner.
This can confuse people but more often brings up interesting aspects and a flexibility of thinking that is beneficial to illuminate a possible trail in unknown territory -*if* people are willing to stretch discussion.
🙂
Michael
Sorry about this, everyone
Okay. This is Keith's thread, not mine, but I feel sort of protective of him and the other nice people posting here. You have asked for it enough times, already. Here it is, even though you so far appear to be immune to the point I will try to make.
You see people painting a picture, simply must vomit on it, and then credit yourself for how interesting the conversation has become. There is no end to the amount of goo guys like you can project onto the boards, and you have a keen eye for prime regurgitation targets. I certainly do have trouble getting used to it.
Anyone can adopt any perspective they wish for excusing a mix of bizarre, often self-aggrandizing, upside down or plainly off the mark statements with bits of truth. In your own mind, doing whatever comes naturally to you may make sense to you, but I think it is a disservice to contributors who are mainly hobbyists with moderate technical backgrounds, who are genuinely interested in expanding their knowledge, and your approach to discourse will just confuse and mislead them. How are they supposed to discriminate between the edible and inedible components?
You may just be helpless to limit your statements to what you know, or to even differentiate what you know from fancy, or just imagine it is going to be clear to everyone when you are just making stuff up, but whatever the case, you are a net negative influence, I'll bet you know this is true, and I wish you would exercise a bit more good citizenship.
Okay. This is Keith's thread, not mine, but I feel sort of protective of him and the other nice people posting here. You have asked for it enough times, already. Here it is, even though you so far appear to be immune to the point I will try to make.
You see people painting a picture, simply must vomit on it, and then credit yourself for how interesting the conversation has become. There is no end to the amount of goo guys like you can project onto the boards, and you have a keen eye for prime regurgitation targets. I certainly do have trouble getting used to it.
Anyone can adopt any perspective they wish for excusing a mix of bizarre, often self-aggrandizing, upside down or plainly off the mark statements with bits of truth. In your own mind, doing whatever comes naturally to you may make sense to you, but I think it is a disservice to contributors who are mainly hobbyists with moderate technical backgrounds, who are genuinely interested in expanding their knowledge, and your approach to discourse will just confuse and mislead them. How are they supposed to discriminate between the edible and inedible components?
You may just be helpless to limit your statements to what you know, or to even differentiate what you know from fancy, or just imagine it is going to be clear to everyone when you are just making stuff up, but whatever the case, you are a net negative influence, I'll bet you know this is true, and I wish you would exercise a bit more good citizenship.
I have to say I find the agrevation here rather disappointing and distracting from the learning process. I believe I am getting my head around the central issue, which is that we have a slug of air bounded by five surfaces and the two largest ones are trying to move it in or out. Motion wise we have leverage in that the air is moving more than the membrane, which is unfortunate when we have a weak motor. This gets compounded because while the motor is compressing air on one side it is rarifying it on the other side, also in an adversely leveraged way.
Have been working on construction and will stay with the idea of metal posts either side of a plastic baffle. The posts on one side will not be bonded to the baffle but to a thinner sheet of plastic surrounding the cut out, but not glued to it. This way shims can be inserted between the baffle and this second sheet to adjust membrane tension without disturbing the post spacing. The posts are 2.8mm diameter which is about 1/9th of an inch. The pleat depth to spacing ratio will be around 5 which is similar to EM AMT's. As I have liquid resistive coating as well as graphite I will be using the former as it will not involve much more work (compared to all conductive pleats) and with masking, should not get all over the place. The open ends could be sealed by injecting epoxy with a syringe.
The opinion that perforations reduce the ES field was Roger Sanders view. Towards the end of Sanders book he proposes a compound ESL, which interestingly, has adjacent membranes supplied with oposite bias polarities and likewise the stators re audio drive. He seems to have the makings of an ES AMT without realising it.
Keith
Have been working on construction and will stay with the idea of metal posts either side of a plastic baffle. The posts on one side will not be bonded to the baffle but to a thinner sheet of plastic surrounding the cut out, but not glued to it. This way shims can be inserted between the baffle and this second sheet to adjust membrane tension without disturbing the post spacing. The posts are 2.8mm diameter which is about 1/9th of an inch. The pleat depth to spacing ratio will be around 5 which is similar to EM AMT's. As I have liquid resistive coating as well as graphite I will be using the former as it will not involve much more work (compared to all conductive pleats) and with masking, should not get all over the place. The open ends could be sealed by injecting epoxy with a syringe.
The opinion that perforations reduce the ES field was Roger Sanders view. Towards the end of Sanders book he proposes a compound ESL, which interestingly, has adjacent membranes supplied with oposite bias polarities and likewise the stators re audio drive. He seems to have the makings of an ES AMT without realising it.
Keith
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Hi,
the single most important advantage of an ESL-AMT I could think of is smaller build width, hence a widened distribution character. Anything else?
jauu
Calvin
the single most important advantage of an ESL-AMT I could think of is smaller build width, hence a widened distribution character. Anything else?
jauu
Calvin
Keith, good to hear you give it a go.
I don't share your concerns regarding low force of the electrostatic principle and its expected adverse outcome in your AMT variant.
In contrary - I see your ESAMT concept as a gorgeous sidestep to the usualy limited SPL capabilities of ESL's as outlined earlier.
Your prototype will show...
Which size for front area are you planning?
Calvin, as you certainly have read, there is a lot of guess working what the benefits may be - possibly it will only "propel the rider two meters straight up into the air" which would be useless in the original intend but fun as well
😉
My own point of view is that ESAMT will (hopefully) work beneficial.
Don't know why not - as relatively low force ribbons for example also can drive horns beautifully - but stability (collapsing membranes) I see the big issue together with setting the pleat depth right (cancellation issue)
Though, with Keith current dimensioning, collapsing - in the sense of film touching - would not be an issue as a membrane of only 15mm pleat depth would hardly reach out 1-2mm even with moderate tensioning IMO - thats quite a bow!
David, your "feedback" is been noticed - though I strongly doubt all *you* vomit there is related to *my* personality.
*and* you seem to not distinguish between my willing to get a good or at least neutral basis on tone of communication and what I criticize/ discuss from your statements that lack backup in specific and important parts as well - strictly on the subject of this thread.
Michael
I don't share your concerns regarding low force of the electrostatic principle and its expected adverse outcome in your AMT variant.
In contrary - I see your ESAMT concept as a gorgeous sidestep to the usualy limited SPL capabilities of ESL's as outlined earlier.
Your prototype will show...
Which size for front area are you planning?
Calvin, as you certainly have read, there is a lot of guess working what the benefits may be - possibly it will only "propel the rider two meters straight up into the air" which would be useless in the original intend but fun as well
😉
My own point of view is that ESAMT will (hopefully) work beneficial.
Don't know why not - as relatively low force ribbons for example also can drive horns beautifully - but stability (collapsing membranes) I see the big issue together with setting the pleat depth right (cancellation issue)
Though, with Keith current dimensioning, collapsing - in the sense of film touching - would not be an issue as a membrane of only 15mm pleat depth would hardly reach out 1-2mm even with moderate tensioning IMO - thats quite a bow!
David, your "feedback" is been noticed - though I strongly doubt all *you* vomit there is related to *my* personality.
*and* you seem to not distinguish between my willing to get a good or at least neutral basis on tone of communication and what I criticize/ discuss from your statements that lack backup in specific and important parts as well - strictly on the subject of this thread.
Michael
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Six factors
I am sorry, Keith. I should have anticipated that my aggravation would bother you. Will rein it in.
That seems to be the basic gist of one of the issues.
Not really an issue. If the posts are stiff enough to handle the membrane tension, the structure should be massive and stiff enough not to be propelled into motion by the ejection of air from one side and intake from the other.
I will try again to describe the situation as I see it:
An ESL membrane must be able to "instantly" assume a position that is proportional to the voltage (force). When radiating into the open air, as waves are generated and propagate away, there is only a small spring load from the local compressibility of the air, plus a small elastic restoring force from membrane tension. The only work done is in compressing the air at the membrane's surface, which is carried away on the sound wave. This is one of the main reasons why well designed ESLs are the most accurate sound transducers.
Imagine a big spring attached to a wall. Think about pushing and pulling on the free end. Pretend the spring and your hand/arm/etc. have no mass. As you push and pull, the compression of the spring follows the force exactly. The moment you increase or decrease the force, the position changes. ESLs and plasma speakers are like that, and are the only examples. Magnetostatic planar transducers come a lot closer than cone speakers do, but are still a pretty far cry.
Now put a big weight on the floor and attach it to the spring. Assume the weight can slide easily on the floor. An exact coincidence between a change in force and a change in position can no longer happen. In this case, you have to do work to accelerate and decelerate the mass, and force is only gradually applied to the spring as the weight moves.
Also, the mass gains momentum -- once you get it moving one way, if you want to get it going the other way, it takes time and energy to decelerate, stop, and accelerate it again in reverse.
If the mass is very big and you decide to change directions very quickly/often, it might never really get started between each time you decide to change directions.
Also, if you let go while it is in motion, it will start bouncing, because the mass will resonate with the spring force.
If you don't want it to bounce, you need a damper, like a shock absorber, a big sail, or just friction with the floor. This consumes even more energy to move.
Now, make the spring so stiff that you can hardly budge it, and we have what I think is something like an ES-AMT.
Here are the six factors that I think will lead to a lack of sound. These are not all completely independent of one another, and 1 and 4 are closely related. All but the last assumes that significant membrane motion is possible, and number 6 is why I think it is not possible.
1) An elevated mass load will be presented by the air that must be accelerated in and out of the slots.
2) There will be viscous damping from flow of air over the surfaces of the membranes and as it exits and enters the mouths of the slots.
3) Mass and viscous loading will not be uniform from the bases to the exits of the pleats. It will be lightest near the exits and heaviest near the bases. Relatively undamped transverse waves will thus be created in the membranes, leading to coloration and distortion.
4) If sound waves were created within the pleat, they would be impeded from traveling outward due to the aspect ratio of the pleat.
5) The pleats will act as resonant cavities, which will put at least one notch and dip in the frequency response.
6) A very much larger than normal spring force will be presented by the air in the slots between the pairs of membranes. This is because the membrane force will be called on to compress and decompress that air by a pinching action before that air has time to accelerate in or out of the pleat.
Sounds good to me.
I doubt he says that as a categorical truth. He knows as well as anyone that field strength and uniformity depend on the gap and the hole diameter (or in his case, slot width).
I am sorry, Keith. I should have anticipated that my aggravation would bother you. Will rein it in.
That seems to be the basic gist of one of the issues.
Not really an issue. If the posts are stiff enough to handle the membrane tension, the structure should be massive and stiff enough not to be propelled into motion by the ejection of air from one side and intake from the other.
I will try again to describe the situation as I see it:
An ESL membrane must be able to "instantly" assume a position that is proportional to the voltage (force). When radiating into the open air, as waves are generated and propagate away, there is only a small spring load from the local compressibility of the air, plus a small elastic restoring force from membrane tension. The only work done is in compressing the air at the membrane's surface, which is carried away on the sound wave. This is one of the main reasons why well designed ESLs are the most accurate sound transducers.
Imagine a big spring attached to a wall. Think about pushing and pulling on the free end. Pretend the spring and your hand/arm/etc. have no mass. As you push and pull, the compression of the spring follows the force exactly. The moment you increase or decrease the force, the position changes. ESLs and plasma speakers are like that, and are the only examples. Magnetostatic planar transducers come a lot closer than cone speakers do, but are still a pretty far cry.
Now put a big weight on the floor and attach it to the spring. Assume the weight can slide easily on the floor. An exact coincidence between a change in force and a change in position can no longer happen. In this case, you have to do work to accelerate and decelerate the mass, and force is only gradually applied to the spring as the weight moves.
Also, the mass gains momentum -- once you get it moving one way, if you want to get it going the other way, it takes time and energy to decelerate, stop, and accelerate it again in reverse.
If the mass is very big and you decide to change directions very quickly/often, it might never really get started between each time you decide to change directions.
Also, if you let go while it is in motion, it will start bouncing, because the mass will resonate with the spring force.
If you don't want it to bounce, you need a damper, like a shock absorber, a big sail, or just friction with the floor. This consumes even more energy to move.
Now, make the spring so stiff that you can hardly budge it, and we have what I think is something like an ES-AMT.
Here are the six factors that I think will lead to a lack of sound. These are not all completely independent of one another, and 1 and 4 are closely related. All but the last assumes that significant membrane motion is possible, and number 6 is why I think it is not possible.
1) An elevated mass load will be presented by the air that must be accelerated in and out of the slots.
2) There will be viscous damping from flow of air over the surfaces of the membranes and as it exits and enters the mouths of the slots.
3) Mass and viscous loading will not be uniform from the bases to the exits of the pleats. It will be lightest near the exits and heaviest near the bases. Relatively undamped transverse waves will thus be created in the membranes, leading to coloration and distortion.
4) If sound waves were created within the pleat, they would be impeded from traveling outward due to the aspect ratio of the pleat.
5) The pleats will act as resonant cavities, which will put at least one notch and dip in the frequency response.
6) A very much larger than normal spring force will be presented by the air in the slots between the pairs of membranes. This is because the membrane force will be called on to compress and decompress that air by a pinching action before that air has time to accelerate in or out of the pleat.
Sounds good to me.
I doubt he says that as a categorical truth. He knows as well as anyone that field strength and uniformity depend on the gap and the hole diameter (or in his case, slot width).
Wow, what a mix of right and wrong explanations of mechanics and acoustics
Agree basically
This is complete fiction, one can also read on several other pages of electrostat sellers.
There simply is no such thing as "instantaneous following of the input voltage signal" with whatever transducer – and besides that it simply is *not* a criterion for good and accurate sound reproduction.
We can go into the very details of mechanics whenever you need an update on that...
Same as above – pure fiction – the "no mass only spring" example is described right but wrongly applied to be also true for ESL's
Learn the technical basics and where they apply properly and where not!
Again - all you describe here is that there is delay between input signal and acoustic output – a universal law that can't be overcome with any transducer whatsoever (not even Plasmas will be an exception!).
In addition you go through what is described by the mass controlled and spring controlled frequency region applying the same way to AMT and ESL and dynamic speakers and for sure to the ESAMT as well – what's the point?
ad 1) sure, but in exchange we only need less air to be pushed by the amount of frontal area to total pleat area.
ad 2) agree, but not being concerned that much about
ad 3) agree on a subtle level but don't agree in practical terms as "normal" AMT's have no tidy bit of problems with this
ad 4) pure fiction - have you ever heard an AMT ?
ad 5) at least one thing we agree on
ad 6) so what? look up for my reply at ad 1)
Michael
Agree basically
This is complete fiction, one can also read on several other pages of electrostat sellers.
There simply is no such thing as "instantaneous following of the input voltage signal" with whatever transducer – and besides that it simply is *not* a criterion for good and accurate sound reproduction.
We can go into the very details of mechanics whenever you need an update on that...
Same as above – pure fiction – the "no mass only spring" example is described right but wrongly applied to be also true for ESL's
Learn the technical basics and where they apply properly and where not!
Again - all you describe here is that there is delay between input signal and acoustic output – a universal law that can't be overcome with any transducer whatsoever (not even Plasmas will be an exception!).
In addition you go through what is described by the mass controlled and spring controlled frequency region applying the same way to AMT and ESL and dynamic speakers and for sure to the ESAMT as well – what's the point?
ad 1) sure, but in exchange we only need less air to be pushed by the amount of frontal area to total pleat area.
ad 2) agree, but not being concerned that much about
ad 3) agree on a subtle level but don't agree in practical terms as "normal" AMT's have no tidy bit of problems with this
ad 4) pure fiction - have you ever heard an AMT ?
ad 5) at least one thing we agree on
ad 6) so what? look up for my reply at ad 1)
Michael
It's stated for laymen. Easier to comprehend and certainly easier to write than a complete description. And the word is instant. And I used quote marks to convey approximation.
The point is that the at audio frequencies, the position lag time is constant and inconsequential.
Sorry to have gone off topic with this, but it sure is a criterion. Another way of looking at it is that there is an absence of nonlinear responses to force.
🙂
It holds true for practical purposes in the audio band for a proper ESL or a plasma speaker. Actually to well into the ultrasound for a plasma tweeter.
LOL
I describe more than that. But I may not have been clear, even yet. No more time after this. Hope it works out for everyone.
An ED-AMT can power its way through the load, but not an ES-AMT.
In that case, no net increase in SPL, and higher capacitance in proportion to the ratio of pleat area to frontal area. No free lunch.
Don't know about you, but I am not concerned much because I think there will be not be enough force to generate flow.
I believe ED-AMT's have enough membrane mass that the air load variation may be a relatively small portion of the total, and its significance would probably 2nd or 3rd order anyway, even with a very low mass membrane. Was just thrown into my list for completeness.
In an ED-AMT, I believe that sound waves are not generated within the pleat, but created by air motion at the slots.
I did not say the slot would be a barrier, just an impedance, and only if sound waves were generated within the pleat (which I think they will not be).
🙂
Well, okay. Boiled down, the first part of my prediction -- not cast in stone, I hope is clear . . . in fact, I hope against hope that this thing works at least a little -- is that there is not going to be enough force to squeeze the air in the pleats significantly. With this air thus left approximately in place, there is only one mechanism left for making sound. That is to generate sound waves inside the pleats that might propagate through the slot and into the open air.
Unfortunately, the only possible motion of the membrane will be normal to the only possible direction of propagation. Since the maximum available force is tiny, the pleats will simply cancel each others motion as they attempt to fire waves at one another across the tiny gap.
A slightly more optimistic way of looking at it is that there will be a velocity null perpendicular to the membranes at the center of the gap, and of course a pressure maximum there whose effective area will be the cross section of the gap. I suppose this could generate a wave perpendicular to the membrane surfaces, but this pressure maximum would be distributed through the pleat from base to exit. It would be lower near the openings where it would encounter less mass and less drag, so some amount of velocity parallel to the membranes may occur, at least near the openings. An interesting picture. My imagination says there will be tiny bit of wave propagating out from within, and a tiny bit of pumping. By this very seat of the pants reasoning, the transducer might be left with an effective radiating area that exceeds its outer area after all.
FWIW, I think regular AMT's are cool and underappreciated transducers. If I am remembering correctly, there is someone in California who is making high output units that are supposed to extend down to something like 200 Hz. It would be great if the same basic concept turned out to be a way to multiply the effective membrane displacement per unit area of an ESL, but it is hard to imagine that the force required for aggressive pumping is available using an electrostatic field.
😀 ad 1, ad 2 . . . you are saying that my unaffordably time consuming attempts at explanation are advertising. Shhh, the sales that pour in when you encourage a hobbyist on a forum are supposed to be a secret.
In order to reduce guess working about ESAMT a little bit further:
Regarding pleat depth, this is IMO the most severe restriction of the AMT principle as it introduces an upper frequency limit not there with flat membranes (like conventional ESL for example)
On the other hand its also the most predictable as the lambda / 4 rule applies like for example with U-frame bass or – more closely to the AMT principle –Axel Ridtahler' stacked RiPole's.
You can look up the math at John Kreskovskys page or at several other places
In case of the 15mm pleat depth chosen I expect the useful bandwidth limited to roughly 4KHz - it will go wild - due to comb filtering - any further up...
Michael
Regarding pleat depth, this is IMO the most severe restriction of the AMT principle as it introduces an upper frequency limit not there with flat membranes (like conventional ESL for example)
On the other hand its also the most predictable as the lambda / 4 rule applies like for example with U-frame bass or – more closely to the AMT principle –Axel Ridtahler' stacked RiPole's.
You can look up the math at John Kreskovskys page or at several other places
In case of the 15mm pleat depth chosen I expect the useful bandwidth limited to roughly 4KHz - it will go wild - due to comb filtering - any further up...
Michael
In a philosophical vein it could be that the numerous people who have independently hit on the idea of an ES AMT with stators (including me) have been too influenced by prior art. EVERYONE knows that an ESL has to have stators!. A bit like early steamships having masts and sails.
Freeing the mind a little gives rise to the following thoughts. We all know that EM forces are strong and ES forces are weak? To extrapolate this to a pronouncement that device A will only work with an EM motor could be fatally flawed, the reason being that it is based on the idea that both motor types are being optimally employed. As the force in an Electro Magnetic motor is the product of the current and Bl we start thinking about a powerful magnet, a small gap, and many turns of wire. This is a very different situation to a real life EM AMT.
The scientific way to evaluate these issues seem to be.
1. Understand the the nature (mass, spring , or both) and magnitude of the load.
2.Calculate the forces available to power this load by EM and ES means.
Immediately we have an issue with comparing apples with apples. If we examine a postage stamp sized and proportioned pleat: in the EM case this implies a huge gap (lowB) and a short single conductor (l). In the ES case things are looking considerably better.
Next we change the shape of the pleat to long and narrow (like a Heil) but keep the area the same. The magnetic gap is reduced and the l is lengthened and the force goes up. What happens to the force of the ES version? Maybe not much except that membrane compliance starts to dominate. Food for thought?
For something completly different we have AES Convention paper 6579 presented at the 119th Convention 2005, New York, by Japanese authors. It is titled "Wideband pietzoelectric rectangular loudspeaker using a tuck shaped PVDF bimorph". US patent 6831985 refers. The paper cannot be posted as it is copyrighted to the AES. It has an uncanny resemblance to the "all moving" AMT but nowhere is AMT or Heil mentioned. Its mode of operation is not described in the paper but its resonance riddled performance is documented at some length. Not having read the patent I suspect that it may get its motion from the pleats opening and closing due to bimorph bending. No mention was made of linearity which probably means that it was embarrassingly poor!
David J, thanks for your animated descriptions of mass and spring loading. One area you loose me in is the mention of wavefronts cancelling in the pleats. I would have thought we are talking acoustically small sizes here and therefore uniform pressure levels everywhere in the pleats.
Keith
Freeing the mind a little gives rise to the following thoughts. We all know that EM forces are strong and ES forces are weak? To extrapolate this to a pronouncement that device A will only work with an EM motor could be fatally flawed, the reason being that it is based on the idea that both motor types are being optimally employed. As the force in an Electro Magnetic motor is the product of the current and Bl we start thinking about a powerful magnet, a small gap, and many turns of wire. This is a very different situation to a real life EM AMT.
The scientific way to evaluate these issues seem to be.
1. Understand the the nature (mass, spring , or both) and magnitude of the load.
2.Calculate the forces available to power this load by EM and ES means.
Immediately we have an issue with comparing apples with apples. If we examine a postage stamp sized and proportioned pleat: in the EM case this implies a huge gap (lowB) and a short single conductor (l). In the ES case things are looking considerably better.
Next we change the shape of the pleat to long and narrow (like a Heil) but keep the area the same. The magnetic gap is reduced and the l is lengthened and the force goes up. What happens to the force of the ES version? Maybe not much except that membrane compliance starts to dominate. Food for thought?
For something completly different we have AES Convention paper 6579 presented at the 119th Convention 2005, New York, by Japanese authors. It is titled "Wideband pietzoelectric rectangular loudspeaker using a tuck shaped PVDF bimorph". US patent 6831985 refers. The paper cannot be posted as it is copyrighted to the AES. It has an uncanny resemblance to the "all moving" AMT but nowhere is AMT or Heil mentioned. Its mode of operation is not described in the paper but its resonance riddled performance is documented at some length. Not having read the patent I suspect that it may get its motion from the pleats opening and closing due to bimorph bending. No mention was made of linearity which probably means that it was embarrassingly poor!
David J, thanks for your animated descriptions of mass and spring loading. One area you loose me in is the mention of wavefronts cancelling in the pleats. I would have thought we are talking acoustically small sizes here and therefore uniform pressure levels everywhere in the pleats.
Keith
I have plans to make ESL-AMT headphone, using rigid stators and completely separated membranes - the "modular" version of this concept.
However, I was sure that AMT's higher frequency limit is wavelength/2, not wavelength/4.. That would mean that a fullrange emitter would have depth of only 4-5 mm and thus, relatively low volume excursion (well, compared to what I've thought).
Nevertheless, I have to make one unit and test it.
Another theoretical question: As I imagine it (don't have enough knowledge), a system with so high adjacent air mass as AMT should exhibit specific loading habits at high K. In a high-K ESL-AMT, air mass would be so high relative to membrane mass, that the amplifier would be, so to say, loaded directly by air, and most of applier power would be converted to acoustic radiation, and ESL capacitative effect would play less in the ESL-AMT model.
Sorry for gibbery explaination, I have to clear up my words.
However, I was sure that AMT's higher frequency limit is wavelength/2, not wavelength/4.. That would mean that a fullrange emitter would have depth of only 4-5 mm and thus, relatively low volume excursion (well, compared to what I've thought).
Nevertheless, I have to make one unit and test it.
Another theoretical question: As I imagine it (don't have enough knowledge), a system with so high adjacent air mass as AMT should exhibit specific loading habits at high K. In a high-K ESL-AMT, air mass would be so high relative to membrane mass, that the amplifier would be, so to say, loaded directly by air, and most of applier power would be converted to acoustic radiation, and ESL capacitative effect would play less in the ESL-AMT model.
Sorry for gibbery explaination, I have to clear up my words.
Spot on.
#############
If the 4kHz upper limit I calculated form your dimensioning holds – and I think it does – we probably could go one step further in the design process and assume a resonance frequency of the film of say 500 Hz to be a good choice to aim towards some 3 decades of usable bandwidth.
Now – my guess about total front area is that you would have to have something at least equal to a 8" driver – for sufficient SPL output of a normal ESL (500 - 4000HZ band width)
For the ESAMT the front area of a (rather rare) 3" mid dome would probably do – roughly a 60x60mm or a 50x80mm or a 20x200mm front area.
If we multiply this 40cm2 (total front area) with the factor 5 (for pleat width versus depth) and a max-p-p excursion of 2.8mm (before touching) and dived by 2 (for non piston like bending of the membranes) we get a theoretical max SPL limit of
120 dB at 500 Hz
155 dB at 4 kHz
(if we plug these numbers into SL's spreadsheet and look up for monopole operation)
Obviously there is plenty of headroom in the mechanic department.
Now – the main question is :
1.) what polarization voltage could be the upper limit for a F-res of 500 Hz and a given membrane dimension regarding stability?
David or anybody having a rule of thumb? – and especially how does ratio of pleat shape count in here?
The second question I would be interested in is how much mechanical excursion can be tolerated in the sense of not over stretching the film (loosening tension by normal operation).
Is there a percentage of elastic stretching known to be safe?
Michael
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Hi,
@nevod
the mass of the esl diaphragm comes into account only in the ultrasonic range for diaphragms of <6µm thickness. Adding dynamic mass can only be counter productive regarding bandwidth.
Designed properly a ESL works into a a real acoustic impedance -the ideal state of affairs- over its complete bandwidth. That´s one of the big advantages over dynamic speakers. So what could folding of the membrane do better than bettering an already ideal state?? You can already say that the amp works ´directly´ on air, since the ESL is called ´massless´ not without reason.
jauu
Calvin
@nevod
the mass of the esl diaphragm comes into account only in the ultrasonic range for diaphragms of <6µm thickness. Adding dynamic mass can only be counter productive regarding bandwidth.
Designed properly a ESL works into a a real acoustic impedance -the ideal state of affairs- over its complete bandwidth. That´s one of the big advantages over dynamic speakers. So what could folding of the membrane do better than bettering an already ideal state?? You can already say that the amp works ´directly´ on air, since the ESL is called ´massless´ not without reason.
jauu
Calvin
Nevod, whoa there, not so fast!. Unless you know something that the rest of us don't we are of the opinion that an ES AMT of any description has never been successfully built by anyone. Rather than thinking of a particular application such as headphones you need to be thinking of an experimental prototype. Maybe you will be the first to report an ES AMT actually making sounds, and that does not include arcing and frying noises!😀
Keith
Keith
Keith Taylor
The 'rigid' version has been built, tested, and works as expected - with seriously enchanced sensitivity, if it is to believe the person who built it - on Russian forum, I can post a link, but there's only text description. I do not know about frequency response though.
Of course, ESL-AMT requires more effort and accuracy than conventional ESL, and I'll build and test an emitter before inserting it anywhere. 🙂
The 'rigid' version has been built, tested, and works as expected - with seriously enchanced sensitivity, if it is to believe the person who built it - on Russian forum, I can post a link, but there's only text description. I do not know about frequency response though.
Of course, ESL-AMT requires more effort and accuracy than conventional ESL, and I'll build and test an emitter before inserting it anywhere. 🙂
Wow! Thats encouraging news. Do you mean enhanced sensitivity of the pleated diaphragm (when pleated) compared to an ordinary ESL of equivalent size, or do you mean the area of the unwrapped AMT for the same area of ESL? Sorry to be testing your English language skills. Do you speak Russian?
Keith
Nevod, link to the forum would be very much appreciated - there is Russian to English conversion on Babelfish.
Results may be funny though...
Michael
Last edited:
Construction progress
Hi All
The Baffle is now complete with the posts in place. It is around 9mm thick and glue laminated from two 4.5mm sheets of PVC. The cutout is 30mm high by 38mm wide. I cut out the membrane and laced it around the posts and marked the post centres with a felt tipped pen. It was here that I started making a few mistakes. The first one was that I did not allow enough time for the ink to dry and smudged it. Mylar does not absorb ink like paper. I put some tension on the membrane by fixing the loose ends with double sided tape. When unlacing the membrane it caught on the sticky double sided tape which I had neglected to remove or cover and some of it stuck to the wanted part of the membrane.
Holding down the membrane with double sided tape I applied masking tape in the form of two passes of office tape over the metalised areas. I suspect that proper masking tape may be better as it comes in wider sizes and the adhesive may not be as agressive. Next followed etching with a Caustic soda solution. Nothing much happened for about 10 minutes then suddenly the metal patches started to appear in isolation and it was done. Removing the masking tape took less of a toll on the membrane than I imagined untill a tear started to appear at the edge of the last pleat. I think it may have been weakened by the double sided tape misshap. Not certain if the membrane can be rescued by some sticky tape but I will go ahead and get some practice in applying the resistive solution. This requires another masking exercise. I figure the corners of the metalised patches where they approach the bias posts may need a small triangular etch to supply an insulating margin, as you are relying on the insulation resistance of the Mylar which may have had the metalisation embedded in it in the the cutting operation.
It seems I may be able to get away with the Sanders?/Waldron? bias supply that I have. Mine had been fitted with parts to give 6KV and I notice the negative side via the 100meg resistor, intended to feed an ESL membrane comes from one side of the power transformer secondary. It is suggested that you refer your chosen voltage to the audio transformer CT. In my case, if I were to choose 3KV that would leave the other 3KV for the positive supply (with another 100M R) The whole thing is floating.
I think I am beginning to overcome a few mental blocks I had about construction difficulties but the masking and lacing/unlacing all take a toll on the membrane.
Keith
Hi All
The Baffle is now complete with the posts in place. It is around 9mm thick and glue laminated from two 4.5mm sheets of PVC. The cutout is 30mm high by 38mm wide. I cut out the membrane and laced it around the posts and marked the post centres with a felt tipped pen. It was here that I started making a few mistakes. The first one was that I did not allow enough time for the ink to dry and smudged it. Mylar does not absorb ink like paper. I put some tension on the membrane by fixing the loose ends with double sided tape. When unlacing the membrane it caught on the sticky double sided tape which I had neglected to remove or cover and some of it stuck to the wanted part of the membrane.
Holding down the membrane with double sided tape I applied masking tape in the form of two passes of office tape over the metalised areas. I suspect that proper masking tape may be better as it comes in wider sizes and the adhesive may not be as agressive. Next followed etching with a Caustic soda solution. Nothing much happened for about 10 minutes then suddenly the metal patches started to appear in isolation and it was done. Removing the masking tape took less of a toll on the membrane than I imagined untill a tear started to appear at the edge of the last pleat. I think it may have been weakened by the double sided tape misshap. Not certain if the membrane can be rescued by some sticky tape but I will go ahead and get some practice in applying the resistive solution. This requires another masking exercise. I figure the corners of the metalised patches where they approach the bias posts may need a small triangular etch to supply an insulating margin, as you are relying on the insulation resistance of the Mylar which may have had the metalisation embedded in it in the the cutting operation.
It seems I may be able to get away with the Sanders?/Waldron? bias supply that I have. Mine had been fitted with parts to give 6KV and I notice the negative side via the 100meg resistor, intended to feed an ESL membrane comes from one side of the power transformer secondary. It is suggested that you refer your chosen voltage to the audio transformer CT. In my case, if I were to choose 3KV that would leave the other 3KV for the positive supply (with another 100M R) The whole thing is floating.
I think I am beginning to overcome a few mental blocks I had about construction difficulties but the masking and lacing/unlacing all take a toll on the membrane.
Keith
