Very interesting indeed! :) Always happy to have more information, even if it doesn't agree with what I've seen in the past.
Erik, I’m aware that there have been measurements of electrostats that apparently showed chaotic diaphragm behavior. Such chaotic behavior would be inherently non-coherent and therefore fall off more rapidly with distance than the signal being produced coherently over the entire diaphragm, which approximates a planar source up close, transitioning to approximating a line source or sometimes a point source as the distance increases.
In other words, if this chaotic diaphragm behavior is "noise", I think the "signal to noise ratio" of an electrostatic panel improves with listening distance, because the noise does not propagate as efficiently as the signal does.
For example, if the bias voltage is up a bit high on the SoundLabs (and/or if your humidity drops significantly), you can hear a waterfall-like sound up close to the diaphragm. This is an incoherent noise, and it does not propagate to the listening position. You can play music at very low volume, down around that waterfall noise floor when you listen with your ear up near the panel, but move back to the listening position all you hear is the music at very low level; the "waterfall" doesn't make it that far.
From measurements I've seen int he past, several ESL's I've seen just don't measure well in the frequency or distortion domains.
That may not be true for every ESL though, that's a broad generalization based on what I've seen.
There were still plenty of good reasons to listen to them though. :)
I've seen frequency response measurements published by Toole for a hybrid electrostat that looked horrendous, but I don't think they were well done, nor the ensuing listening test. Here's why:
SPL will fall off more rapidly with distance from the point-source woofer than from the line-source panel. So a hybrid electrostat either has to be designed to be a good match for its target room size (NOT the big spin-o-rama room that Harmon uses), OR it has to be carefully adjusted to work well in that particular room.
In the Harmon test, I believe it was an essentially non-adjustable Martin Logan hybrid electrostat, and the room was many times too large for it. Also the listeners sat side-by-side and the Martin Logans had as small sweet spot, so that further handicapped it in the listening evaluation.
Not that I'm the world's biggest Martin Logan fan, but imo they were not properly evaluated in that test.
I think we are debating technology and not the sound. I think listeners should try out an ESL / Amp combination and see if the like them for the money.
While you do have to carefully match the woofer's level to the panel, the issues I'm talking about have more to do with ragged frequency responses within the panel itself, especially between the mid to treble range. Something a number of people have tried to correct with room correction software with varying levels of success.
I don't think this should matter as much as personal listening experience however. I'm just trying to be clear about spepcmanship.