A history question about planar drivers

I believe that a speaker using the electrostatic approach came before the magnetic cone speaker. We are talking about the early years of the last century.

Yes, the design of electrostatic speakers is much older. There were experimental models in the Bell labs back in the 1920s.

Janszen tweeters were available in the early 1950s and Peter Walker came out with the Quad in the mid 1950s.

That's very interesting - especially that electrostatics predated what are now "conventional" cone drivers.

Another thing that caught my eye is that the planar magnetic design was originated by Jim Winey in 1969, yet Infinity, Apogee, and others were creating planar magnetic designs long before his initial patent should have expired.

Perhaps because he was working at 3M at the time prevented him from successfully completing the patent (the Magnepan factory tour does not explicitly state so), or perhaps it's a bit more complicated than that and his patent was narrow enough in scope that the other companies got around it.

I'm not a patent expert, but in general, one can not patent an "idea" but rather just a specific implementation of it.

As for the conventional cone driver as we know it today, that was also patented in the US in 1924 by Rice & Kellogg. However, the moving coil design dates to Oliver Lodge, a British physicist, in 1898 and other electric drivers go back to the 1860s, but they were for the telephone.

My first thought here is that (using your terms) the "idea" is reproducing sound and the specific implementation is a thin membrane impregnated with a wire coil, suspended between magnets and caused to vibrate by applied AC current.

The U.S. Code states:

Whoever invents or discovers any new and useful process, machine, manufacture, or composition of matter, or any new and useful improvement thereof, may obtain a patent therefor, subject to the conditions and requirements of this title.

I'd say that the concept and invention of the planar magnetic driver fits into that category quite clearly.

However, Magnepan could have missled its patent application and perhaps limited it to full-range drivers (or some other possibly unnecessary specificity) that gave the other manufacturers a loophole.

I did read a thread I found via Google that stated that Magnepan sued Apogee over one of its designs, but that it was settled out of court eventually.