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.
You have to realize that acoustic transparency of a perforated stator is actually very high so you can't just look at this from the perforation area ratio. a perforated plate like estat stator pretty much do not block any sound.
Furthermore, in case of a driver like the k1000, the large discontinuity at the edge of the driver frame generates its own set of issues, one of which is major: acoustic diffraction. If you take something like HD800, the micro-perforated baffle plate and high absorption from the earpad actually make it much less prone to these issues, which probably partly explains why it images so well.
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.
The main issue is not the oversimplified bit but rather misleading argumentation. I mean, in terms of physics (in the sense of vibro-acoustics and sound propagation/ diffraction), I don't see the points you're trying to make. If I then go by subjective impressions, it turns out I could feel like a speaker being driven next to my face when I sampled it, which would mean it can't be the perfectly acoustically transparent transducer you're claiming it to be.
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.
I was laughing when I read your comment about carbon nanotubes, and I am glad you clarified later in the thread about this referring to the future, possibly in your lifetime . Now imagine what kind of thin estat diaphragm we may be able to come up with through similar advances in material science .
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 ).
The amplifier gurus should answer this one, but this HF limitation is only effective if you're trying to make an estat transducer for bats. Within the realm of audible audio (say 20kHz to be very conservative), I believe amps like the BHSE and other T2 actually have no issue with any of the stat phones.
Also, the effective mass is indeed affected by the air trapped in front of the diaphragm at low frequency but that certainly isn't true at high frequencies. The high frequency response of the transducer is limited by the diaphragm mass, not that of the air layer around it. This is another huge advantage of estats (and clearly audible too, take the example of cymbal shimmer): the moving mass is orders of magnitude lower than any dynamic or ortho driver for that matter (that is until carbon nanotubes transducers eh ).
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.
Is there some reference for this mysterious phase shift for stat amps at high frequency due to current limitation? You mean limited slew rate?
Talking about phase shift, what do you make of the low pass filter used to compensate for acoustic cancellation of the front/back waves in the k1000? If anything, this passive electrical network is at least introducing 90 degrees phase shift from the mids up, isn't it?
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 ...
I am all for the k20000, but your claim of the k1000 being unsurpassed is surreal. It is a special experience due to the natural xfeed but other than that I don't see it. As for good recording, it is a good point as the k1000 is for instance unusable with binaural recordings.