math/science help re Henry W Parker

[moray james]

Would appreciate some help to establish if the math behind the Henry W Parker patent is correct. My math skills are not up to this. Found Parkers patent years ago and have been facinated since. Have built several small crude versions which do work but not very well. Have been trying to figure out how to build one of these that really worked well.
Henry W Parker US patent number 2,864,899 date Dec. 16, 1958. Parker claims "a substanttially constant air gap, three electrode, electrostatic loudspeaker comprising an insulated studded diaphragm electrode, held in constraint by frame clamped edges, midway between two opposite separately insulated cooperating forminated planar outer electrodes fixed parallel to the plane of the diaphragm, the said diaphragm studded on both sides with a plurality of straight sided right prismatic projections partially inserted in regestered straight sided clearance holes in the said forminated outer electrodes." Parker claims that this design creates a speaker which has a linear function between sound presure and the applied voltage all the way from the infrasonic to the ultrasonic.
I tried to track Parker down about 15 years ago with no success nor did I find other work or patents. The patent is a good read. I would appreciate any comments or discussion about this if there is any interest hers. Best regards Moray James.

[SY]

The math looks straightforward but doesn't address the main issue: how to move a now-massive diaphragm efficiently. The motor force of an ESL is pretty low, thus the need for very lightweight diaphragms.

[moray james]

Sy: thanks for the help. Have thought about this patent for a long time. The best possible solution that I can see is in a vacume formes diaphragm where the digits ar some how reinforced. Would think that a fairly stiff material would be required. Not much of a DIY project but the concept is very interesting. There have been a number of manufactured diaphragms of a similar nature used for magnetic drive speakers and though they do have strong motors there is the conductor weight to consider. The fact that this would not be the worlds most efficient ESL is however offset by the long linear drive available and there is also the possibility of horn loading to bump the gain. You are probably right though that in all these years nothing has come to market for the issue you raise. Thanks again for your input. Maybe there is a clever soul out there with some fresh ideas? Best regards Moray James. PS did you have a look at the Zelec by Du Pont?

[SY]

Haven't looked at Zelec yet, sorry.

Thermoforming is great as long as you have reasonably thick material with some structural integrity. But that means mass, alas.

[I_Forgot]

Originally posted by moray james
The fact that this would not be the worlds most efficient ESL is however offset by the long linear drive available and there is also the possibility of horn loading to bump the gain.

The point of all this is to get flat response from the ESL, isn't it? How will sticking a horn in front of the thing help with that?

The rising response of an ESL panel is predictable and can easily be compensated for with an inexpensive low pass filter. Why muck it up with additional mechanical complication and cost to achieve the same result?

I_F