[analogsurviver]

Quote:

Hello to All and especially to Analogsurviver,
 
Of course it's very attractive for an old headphone designer like me to create a K2K based on latest technology.
 
On the other hand, I pesonally hate to much risk.
Risk for me are not so much in commercial terms, because I really know how to manage proper those approach.
The main risk would be to get the right acoustic setup for most of you audiophil people, so that you would be finally really satisfied and really willing to buy such a product for a premium.
The idea of paying a kind of deposit for all interested one which would be payed back of course, sound basically a quite simple model for the development investment. But how to judge the final product and not at least to fix the target ...?
F.I. and as you know, those effects like spatial (three dimensionality) listening are still not measurable... Also human has different audiophil tast (f.i. In the U. States, England and Germany those tastes are really quite different)....
 
To build different K2K versions would be of course also possible, but again how to judge which one should be finally build...?
 
Any idea of you great formum?
 
BR heinz

Glad to see your response.
 
Well, tastes are and will remain different. K1000 and whatever can be made today based on the idea will never be a basshead can - no matter what. I could post at least 2 musical samples that, although admittedly extreme, will K.O. K1000 and K2K and K(n+1)K  ( n being number high enough for even the most stubborn to stop trying the impossible ) - in about 2 seconds. I believe what is achievable today is to make K2K to perform on pop/rock/etc at least kind of holding its own against other state of the art designs of today. Say - "surviving" the latest Yello album without falling to pieces during loud/bassy passages. 
 
The forte of K1000 is in acoustic, particularly vocal music. Here it reigns with such superiority over anything else ( I did not hear ..... and .... and ...; but if it uses earpads - can not be better ) that it is quite scary. If K2K menages to get the Metal Grill Blues right ( please see the very thruthful assesment of K1K in
 
 http://www.head-fi.org/t/634201/battle-of-the-flagships-50-headphones-compared
 
and improve on bass, I firmly believe there will be enough customers. Throw in a bit less demanding drive and perhaps a bit better/extended/more delicate high
frequency  response ( too achievable given today's technology in my opinion ) - you would have to create quite a waaaaaaiiiiti.................ng list. 
 
In case that during development shows up that various versions optimized for various music can not be united in a single version - why not build at least two, one for acoustic and another for more modern amplified music? The genres requiring orthodynamics will be out of reach of any K2K version
anyway - so if it is only one version to be built, please choose the one optimized for the acoustic, where K1K design/concept is at the strongest.
 
But please - do not try to decrease the demand in order to be able to produce K2K by setting the price tag out of reach of majority. It will remain a niche product, aimed at or near very top level - TBH, it is not as costly to produce as some premium electrostatic design and pricing , regardless of potential (and hopefully achieved ) sonic superiority, should reflect that. I particularly feel that many MUSICIANS, not necessirily audiophilles alone,  would be interested - if given the possibility to audition K2K under proper conditions.
 
One suggestion - when recording in 2008 a "little known village orchestra" , sometimes reffered to as Wiener Philharmoniker, both the Dirigent and Konzermeister were amazed at the quality of the binaural recording of the rehearsal ( all I could get the permission to officially do ) , played back through K 1000. THEY SAW/HEARD AKG K1000  FOR THE VERY FIRST TIME !!! 
 
Reffering to WP as "little known village orchestra" is of course a joke - hopefully K2K will not be such a promotional joke as K1K obviously has been, at least as far as WP is concerned; if my memory serves me well, both WP and AKG come from the same -  town...! 
 
So - how about letting all the players/conductors of the WP to buy a pair of K2K ( personalized, with first and last name engraved ) at cost, say 1/3rd of the retail price, in exchange for some really good promotion?  That could go from the photo of the entire orchestra on stage wearing K2Ks to some extraordinary recordings made to show off K2Ks to the maximum of the ability.
 
 I can not think of anything better, given the circumstances. Beats Beats by Dre in my book.

 

[complin]

Yes but what sort of drivers would be used? Dynamic, Ortho or electrostatic?
 
Ortho I think might prove too heavy for such a design?  Dynamics have come a long way in terms of materials and the types of magnets used.
This might sound outlandish but what about adapting an existing design that has some of the principles of the original K1000...... like the Jecklin!
 
QUAD Musikwiedergabe in Germany are making the new version of the original Jecklin but with the panels fixed in a very similar fashion.  If this was adapted so that the transducers could be swiveled out in the same way as the original K1000 could this be a staring point? Perhaps the Jecklin panels might be too large, I know its not as simple as this and that other modifications would probably need to be done.
What are Heinz thoughts on such an approach 

 
Quote:

Hello to All and especially to Analogsurviver,
 
Of course it's very attractive for an old headphone designer like me to create a K2K based on latest technology.
 
On the other hand, I pesonally hate to much risk.
Risk for me are not so much in commercial terms, because I really know how to manage proper those approach.
The main risk would be to get the right acoustic setup for most of you audiophil people, so that you would be finally really satisfied and really willing to buy such a product for a premium.
The idea of paying a kind of deposit for all interested one which would be payed back of course, sound basically a quite simple model for the development investment. But how to judge the final product and not at least to fix the target ...?
F.I. and as you know, those effects like spatial (three dimensionality) listening are still not measurable... Also human has different audiophil tast (f.i. In the U. States, England and Germany those tastes are really quite different)....
 
To build different K2K versions would be of course also possible, but again how to judge which one should be finally build...?
 
Any idea of you great formum?
 
BR heinz

 

[analogsurviver]

Quote:

Yes but what sort of drivers would be used? Dynamic, Ortho or electrostatic?
 
Ortho I think might prove too heavy for such a design?  Dynamics have come a long way in terms of materials and the types of magnets used.
This might sound outlandish but what about adapting an existing design that has some of the principles of the original K1000...... like the Jecklin!
 
QUAD Musikwiedergabe in Germany are making the new version of the original Jecklin but with the panels fixed in a very similar fashion.  If this was adapted so that the transducers could be swiveled out in the same way as the original K1000 could this be a staring point? Perhaps the Jecklin panels might be too large, I know its not as simple as this and that other modifications would probably need to be done.
What are Heinz thoughts on such an approach 

 

Well, Jecklin has been benchmark for the K1K team during development. One ,but absolutely crucial, advantage of K1K driver over ANYTHING else, is its acoustic openess - IIRC, just below 80%. An electrostatic driver can in theory achieve maximum 50 % acoustic openess - still too small. I owe you and another poster from the Stax Unwanted thread the explanation behind this acoustic openess and why it is co crucial in achieving (almost ) totally transparent SQ only K1000 is able to offer at the time. It is the original review of K1K in Swiss magazine Hi-Fi Video 3/90 by Walter P. Gross. Part of this review is quoted on official AKG site. It is in German and I will try my best to translate it into nonbabblefish English to the best of my ability. I will try to do it in not too distant  future.
 
But, suffice is to say one thing: Swiss are notorious for their patriotism, it is evidenced wherever you look.  They are VERY reluctant to admit that anything non-Swiss is better than their best offering(s). Throughout the review, constant reference to Jecklin Float is made. Here the ZUSAMMENFASSUNG ( verdict ) :
 
The AKG K 1000 headphone, developed after completely new criteria, is not only built to the highest standards - and thanks to reasonable adjustability, especially comfortable to wear, but also sounds at the highest possible level. It should be the most technically and acoustically accomplished headphone in the world market at the time (1990) and is recommended both for professonals as well as for the very demanding music lovers.
 
In a PM to Heinz, I have disclosed the reasons behind my decision to try to bring K2K about and offered my help; it is a very interesting story, to be revealed only if and when the overall conditions ever get "ripe". But - it essentially boils down to: If you can't beat them, join them ...

 

[complin]

Not exactly sure what you mean by acoustic openness unless you are referring as to how the drivers are mounted?  But that was my point, modify how the drivers are mounted and could be positioned?
 
I relation to acoustic performance IMO nothing can match an electrostatic be it loudspeaker or headphone in overall performance.  The only area some may be critical of are visceral bass impact.
However; in speed, transparency and rendition of true detail I believe they have no peers.  They can also act as a true point source like the Quad 57 which is what I would have thought be required for a K2K to maximise performance? 
 
Quote:

Well, Jecklin has been benchmark for the K1K team during development. One ,but absolutely crucial, advantage of K1K driver over ANYTHING else, is its acoustic openess - IIRC, just below 80%. An electrostatic driver can in theory achieve maximum 50 % acoustic openess - still too small. I owe you and another poster from the Stax Unwanted thread the explanation behind this acoustic openess and why it is co crucial in achieving (almost ) totally transparent SQ only K1000 is able to offer at the time. It is the original review of K1K in Swiss magazine Hi-Fi Video 3/90 by Walter P. Gross. Part of this review is quoted on official AKG site. It is in German and I will try my best to translate it into nonbabblefish English to the best of my ability. I will try to do it in not too distant  future.
 

 

[analogsurviver]

Quote:

Not exactly sure what you mean by acoustic openness unless you are referring as to how the drivers are mounted?  But that was my point, modify how the drivers are mounted and could be positioned?
 
I relation to acoustic performance IMO nothing can match an electrostatic be it loudspeaker or headphone in overall performance.  The only area some may be critical of are visceral bass impact.
However; in speed, transparency and rendition of true detail I believe they have no peers.  They can also act as a true point source like the Quad 57 which is what I would have thought be required for a K2K to maximise performance? 
 

Well, here is the catch -  acoustic openess.  If you LOOK at the driver(s), you will see that they are not visibly transparent - there will be some "shadow" due to diaphragm, mounting/supportring structure(s), frames, pads etc etc - which is normal. If nothing, with zero size, would be able to produce sound  as heard by ,istening to say live music, that would present an ideal transducer. Anything bigger than zero will have more or less of an acoustic shadow, in addition to reflection between itself and our earss/pinnae, if we talk about headphones/eraspeakers. That acoustic openess should be as high as possible , but certainly exceeding 50 % . 50% is theorethically possible with ESL - in an transducer where stators are composed of rods of the same diameter as it is free open space  - that gives 50 % acoustic openess. Real ESL driver would have to include some surface around the effective diaphragm area, in order to accomodate clamping for the diaphragm, electrical contacts as well some form of increasing the rigidity of the whole structure, bringing acoustic openess below 50 % in real world designs.
 
Look at the K1000 driver - there is practically nothing to be seen - they ingeniously were able to increase the acoustic openess to just below 80 %, a figure unmatched to this day. Since you do have K1000, Jecklin Float and Stax (any, does not matter in this case which model )), you can do a very simple test.. Play some music over loudspeakers or simply listen to the conversation ia a room - first without anything, just your ears, then put on K 1000, then Foat, then Stax - WITHOUT phones being connected to appropriate source. . You will hear that putting K1000 on your head will have very little, if any, sonic effect. If you hear any significant diference, congratulate yourselves - your hearing above 15 kHz is still going VERY strong.. Putting on Jecklin Float should have a marked awareness of "something" being acoustically present close to your ears - you are hearing ESL drivers, which are in Jecklin Float case an equivalent of a 10 by 10 cm square plate. This condition is still far more acoustically transparent than any Stax that use earpads. 
 
This was of coure oversimplification of the problem, but it goes to show just what is happening when we try to listen with heasdphones/earspeakers - which is not nature has equipped us for. The very perception of our hearing, with which we have learned to hear, is considerably distorted by any cans - it is just K1000 almost gets away with it  far better than ANYTHING else.
 
Of course, electrostatic principle is superiour to dynamic one - in theory, at least. However, practical liumitations are rendering this gap esl has ever smaller - new materials for the diaphragm of dynamic drivers, such as carbon nano tubes, have raised the bar for the dynamic drivers to hitherto unheard of levels - the piston like behaviour of the membrane is now possible without any appreciable breakup far higher in frequency than ever before. This is due to order(s) of magnitude better mechanical characteristics for the carbon nano tubes compared to any material used before.
 
In order for the esl to work, you need voltage - AND current. As an esl is practically pure capacitance in electrical terms, that means you need ever more current whenever you increase the frequency.  That means you would have to have infinite power available from the "amplifier" driving the esl if it is to reproduce highs perfectly. Even this condition, which can not be realized in practice, assumes there are no HF loss due to mass of the esl driver ( largely composed of the air trapped inside driver itself, can not be appreciably lowered with diaphragm material, moving mass of an esl is largely the layer of air that is governed by the design chosen as tradeoff among low and high frequency limits and efficiency ).
 
I gave up at about 500-600 VA constant power consumption being needed to drive a single pair of Jecklin Floats. Direct drive high voltage output transformerless amp - FAR better any transformer can possibly hope to achieve. Dangerous, lethaly so - many times over. Even with this behemoth, esl highs are still a bit softer than the real thing - the inevitable consequence of the phase shift you get when not using ideal infinite power drive for the esl. The laws of physics and electricity are what they are and we can not do anything about it.
 
Even if a perfect electrostatic driver existed, there is no way of driving it perfectly.
 
Quad 57 is no doubt one of the very best speakers in existance - but NOT the best. There is / was variation on the theme, called  Massless Force Field Speaker, by John Iverson in the USA, as well as rumors about something similar by Nelson Pass. Both were said to be the best ever heard by very select few who were allowed to hear ( but generally not see ) them.
Both required extreme amounts of power, on the order of kilowatts, due to extremely low efficiency, and there were other reservations that prevented this idea ever reaching anything like commercial availability. But those who did get to hear them said there is simply nothing comparable.
 
All of which brings us back to the dynamic driver -  although imperfect in theory, current state of tecnology should allow dynamic driver to reach and exceed performance from electrostatics which are in practice limited by amplification - there is no high frequency limit for amplifiers designed for dynamic drivers that could possibly lead to audible degradation of the signal - MHz bandwidths are quite common and nothing special anymore. 
 
K 1000 driver is NOT perfect - some would go as far as to say it is outdated.  Even so, whenever used within design envelope, it will sound superiour to anything else given good recording.
 
Now imagine what K2K, retaining all the positive aspects of K1K, with all the latest tech tricks developed in 23 years since the introduction of K1000,  could bring to the table ...

 

[ruinevil]

The Nelson Pass electrostatic speakers gave him ozone poisoning.... but he says they sounded awesome.
 
It could have been the oxygen depletion causing auditory hallucinations though.

 

[Donald North]

Planar transducers including electrostatics are fixed around their perimeters and consequently don't move uniformly across the diaphragm. Dynamic transducers, by comparison, have suspension components allowing the diaphragm the possibility to move uniformly.

 

[wuwhere]

Quote:

Planar transducers including electrostatics are fixed around their perimeters and consequently don't move uniformly across the diaphragm. Dynamic transducers, by comparison, have suspension components allowing the diaphragm the possibility to move uniformly.

 
Full range Apogee ribbon speakers' mids and tweets are only fixed at the top and bottom. I can't recall how the bass ribbon is attached.

 

[complin]

So dynamics are more uniform driven from just the center or the edge? 
Electrostatics are drive across the whole diaphragm 

---

Quote:

Planar transducers including electrostatics are fixed around their perimeters and consequently don't move uniformly across the diaphragm. Dynamic transducers, by comparison, have suspension components allowing the diaphragm the possibility to move uniformly.

 

[Donald North]

Dynamics are driven by the voice coil. Depending on its diameter, it could be towards the center, middle, or outer edge. Because the diaphragm has a suspension, it has the potential to move uniformly, depending on the diaphragm geometry and material. Tweeter domes can operate pistonic to above 20kHz before they start bending modes.
 
Electrostatics are driven essentially uniformly across the diaphragm, however the diaphragm doesn't move uniformly because the edges are clamped.
Quote:

So dynamics are more uniform driven from just the center or the edge? 
Electrostatics are drive across the whole diaphragm 

---

 

[arnaud]

This is an interesting point of view but the numerous claims merit adressing. In another post...

Well, here is the catch -  acoustic openess.  If you LOOK at the driver(s), you will see that they are not visibly transparent - there will be some "shadow" due to diaphragm, mounting/supportring structure(s), frames, pads etc etc - which is normal. If nothing, with zero size, would be able to produce sound  as heard by ,istening to say live music, that would present an ideal transducer. Anything bigger than zero will have more or less of an acoustic shadow, in addition to reflection between itself and our earss/pinnae, if we talk about headphones/eraspeakers. That acoustic openess should be as high as possible , but certainly exceeding 50 % . 50% is theorethically possible with ESL - in an transducer where stators are composed of rods of the same diameter as it is free open space  - that gives 50 % acoustic openess. Real ESL driver would have to include some surface around the effective diaphragm area, in order to accomodate clamping for the diaphragm, electrical contacts as well some form of increasing the rigidity of the whole structure, bringing acoustic openess below 50 % in real world designs.

Look at the K1000 driver - there is practically nothing to be seen - they ingeniously were able to increase the acoustic openess to just below 80 %, a figure unmatched to this day. Since you do have K1000, Jecklin Float and Stax (any, does not matter in this case which model )), you can do a very simple test.. Play some music over loudspeakers or simply listen to the conversation ia a room - first without anything, just your ears, then put on K 1000, then Foat, then Stax - WITHOUT phones being connected to appropriate source. . You will hear that putting K1000 on your head will have very little, if any, sonic effect. If you hear any significant diference, congratulate yourselves - your hearing above 15 kHz is still going VERY strong.. Putting on Jecklin Float should have a marked awareness of "something" being acoustically present close to your ears - you are hearing ESL drivers, which are in Jecklin Float case an equivalent of a 10 by 10 cm square plate. This condition is still far more acoustically transparent than any Stax that use earpads. 

This was of coure oversimplification of the problem, but it goes to show just what is happening when we try to listen with heasdphones/earspeakers - which is not nature has equipped us for. The very perception of our hearing, with which we have learned to hear, is considerably distorted by any cans - it is just K1000 almost gets away with it  far better than ANYTHING else.

Of course, electrostatic principle is superiour to dynamic one - in theory, at least. However, practical liumitations are rendering this gap esl has ever smaller - new materials for the diaphragm of dynamic drivers, such as carbon nano tubes, have raised the bar for the dynamic drivers to hitherto unheard of levels - the piston like behaviour of the membrane is now possible without any appreciable breakup far higher in frequency than ever before. This is due to order(s) of magnitude better mechanical characteristics for the carbon nano tubes compared to any material used before.

In order for the esl to work, you need voltage - AND current. As an esl is practically pure capacitance in electrical terms, that means you need ever more current whenever you increase the frequency.  That means you would have to have infinite power available from the "amplifier" driving the esl if it is to reproduce highs perfectly. Even this condition, which can not be realized in practice, assumes there are no HF loss due to mass of the esl driver ( largely composed of the air trapped inside driver itself, can not be appreciably lowered with diaphragm material, moving mass of an esl is largely the layer of air that is governed by the design chosen as tradeoff among low and high frequency limits and efficiency ).

I gave up at about 500-600 VA constant power consumption being needed to drive a single pair of Jecklin Floats. Direct drive high voltage output transformerless amp - FAR better any transformer can possibly hope to achieve. Dangerous, lethaly so - many times over. Even with this behemoth, esl highs are still a bit softer than the real thing - the inevitable consequence of the phase shift you get when not using ideal infinite power drive for the esl. The laws of physics and electricity are what they are and we can not do anything about it.

Even if a perfect electrostatic driver existed, there is no way of driving it perfectly.

Quad 57 is no doubt one of the very best speakers in existance - but NOT the best. There is / was variation on the theme, called  Massless Force Field Speaker, by John Iverson in the USA, as well as rumors about something similar by Nelson Pass. Both were said to be the best ever heard by very select few who were allowed to hear ( but generally not see ) them.
Both required extreme amounts of power, on the order of kilowatts, due to extremely low efficiency, and there were other reservations that prevented this idea ever reaching anything like commercial availability. But those who did get to hear them said there is simply nothing comparable.

All of which brings us back to the dynamic driver -  although imperfect in theory, current state of tecnology should allow dynamic driver to reach and exceed performance from electrostatics which are in practice limited by amplification - there is no high frequency limit for amplifiers designed for dynamic drivers that could possibly lead to audible degradation of the signal - MHz bandwidths are quite common and nothing special anymore. 

K 1000 driver is NOT perfect - some would go as far as to say it is outdated.  Even so, whenever used within design envelope, it will sound superiour to anything else given good recording.

Now imagine what K2K, retaining all the positive aspects of K1K, with all the latest tech tricks developed in 23 years since the introduction of K1000,  could bring to the table ...

 

[Don Quichotte]

Yep, I was going to write in this post about what you called "acoustic openness". I was trying to remember what was it called like in the AKG K1000 brochure.
 
Mr. Designer of the K1000: how important was this principle of achieving the best possible acoustic openness during the development of the K1000? I mean, I know it was used as a selling point, but I feel it received little recognition among the audiophiles, or at least less than it deserves. Everybody talks about the soundstage width and some even mention imaging (while others claim imaging isn't that great, and I tend to agree), but only few head-fiers talk about how clean is the sound and to what amazing degree you seem to hear only the driver. To me, this is one of the most distinguishing features of the K1000, along with its macrodynamics / sound "tactility".
 
Was this acoustic openness a very important design objective you had from the beginning, or were you more after natural crossfeed, out of head soundstage and the acoustic openness was more like a welcome side effect of not needing pads around the ear anymore and you capitalized on this by a few other clever design tricks?
 

 

[complin]

As you has the potential BUT is there any objective data to show it is superior to an electrostatic diaphragm?
 
My ears tell me otherwise, but it would be good to have some objective data to back up either theory 
 
Quote:

Dynamics are driven by the voice coil. Depending on its diameter, it could be towards the center, middle, or outer edge. Because the diaphragm has a suspension, it has the potential to move uniformly, depending on the diaphragm geometry and material. Tweeter domes can operate pistonic to above 20kHz before they start bending modes.
 
Electrostatics are driven essentially uniformly across the diaphragm, however the diaphragm doesn't move uniformly because the edges are clamped.

 

[analogsurviver]

Quote:

Planar transducers including electrostatics are fixed around their perimeters and consequently don't move uniformly across the diaphragm. Dynamic transducers, by comparison, have suspension components allowing the diaphragm the possibility to move uniformly.

+1. The ONLY way to adress this problem is the Beveridge electrostatic ( with an extremely  comfortable margin, the most accurate overall commercially available speaker in history, when played within its loudness capability  - but only models driven directly with the high voltage OTL amp ) with its "upside down ESL principle". Contrary to most ( all ? ) other ESLs that have low impedance stators and high impedance diaphragm, Beveridge reverses that by having a metallized low impedance diaphragm and stators made of high impedance material. This way, by employing feedback, the amplifier can adjust the drive across of the diaphragm  differently DOWN TO A SINGLE MOLECULE, thus correcting the distortion planars introduce due to clamped circumference of the diaphragm. This is impossible with normal ESLs. 
 
I would have too look up for the measurements done in Germany in late 70s - they measured the SPEAKER WITH MICROPHONE IN AN ANECHOIC ROOM. Distortion of the speaker acoustic output measured with microphone has been on the order of 0,0X % for the second harmonic and 0,00X % for the third, from about 100Hz to 10 kHz and close to its maximum output.
 
Bev has the most accurate dynamic range reproduction in the world, when its loudness capabilizies are not exceeded. Sadly, it can play only to about the level required by some mid-size volume Mozart symphony when fed with an uncompressed recording. Forget Mahler's second. But what is below its clipping point down to the threshold of the audibility, is handled with an absolute aplomb. Not perfect, best - yes.
 
Provided a headphone stator/transducer using Bec technology could be made, it would have been a step in the right direction in order to improve present day simple electrostatics. 
 
However, there is no way around the acoustic openess issue of ESL. Here, Bev is equal with its less evolved brethern.
 
K2K.

 

[analogsurviver]

Quote:

As you has the potential BUT is there any objective data to show it is superior to an electrostatic diaphragm?
 
My ears tell me otherwise, but it would be good to have some objective data to back up either theory 
 

In theory, ESL principle that drives the diaphragm uniformly across the whole surface, down to a molecule level, is of course superiour to dynamic principle that has to rely on piston like motion of the diaphragm that is driven most usually by the "circle" of contact with the coil, be it outer edge or any other place designers found the best compromise to drive the diaphragm as best as they can. ESL is next to ( see my post regarding clamped circumference of planars ) perfect by design, dynamic might actually achieve this one day through execution, by using truly advanced diaphragm material. Carbon nano tube technology might well be the answer to get "perfect enough" diaphragm, say one really good/essentially flat  to at least 50 kHz, with very smooth response falling gently above that point to
beyond 100 kHz. Perhaps not tomorrow, but hopefully I will get to hear it during my remaining lifetime.
 
And yes, the driver of K1000 can be regarded as the world's best full range tweeter - with an + - 3 mm ( or thereabouts ) excursion. It is rather raw sounding compared to the ESLs - but much of this difference audible when compared to ESLs is not due to the driver itself, but to "everything else" that comprises K1000 design as a whole.
 
Bearing in mind it is the only sole representative of its kind, against n-th re-iterations of the ESL design by many manufacturers,  with no MK II varsion at all, and can still , with all of its many imperfections, menage to mount such an oposition, is comment enoug regarding the brilliance of the idea behind its design.