A history question about planar drivers

The Magnepan web site states that Magnepan founder Jim Winey developed the magnetic planar speaker and founded the company in 1969.

He had heard and liked electrostatic speakers, but as an engineer at 3M at the time, he thought there might be a way to drive the film magnetically instead of electrostaticly. He quit 3M, started Magnepan, and patented the product.

There is a link on the Magnepan website to a SoundStage! article on the company and discusses the product's history.

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.

In reference to patents, the devil is certainly in the details. I believe that patent law is one of the relatively few official subspecialties in law practice; it requires special authorization to practice before the Patent Office.

I don't know that Audiogon is a particularly authoritative venue to debate the merits of a patent's scope....

;-)

Good point.

Regardless, it would be interesting to find out the specifics behind how other companies began using planar magnetic drivers (legally and otherwise).

12-02-10: Mlsstl
In reference to patents, the devil is certainly in the details. I believe that patent law is one of the relatively few official subspecialties in law practice; it requires special authorization to practice before the Patent Office.

I don't know that Audiogon is a particularly authoritative venue to debate the merits of a patent's scope....

As usual, Mlsstl's comments are well put and correct on all counts. I say that as a licensed patent attorney.

FYI, all U.S. patents that have been issued since 1790 can be searched and viewed at the U.S. Patent and Trademark Office website, although the parameters that can be entered into the search fields for patents issued prior to 1976 are very limited.

A search under "Magnepan" returns these patents. I haven't looked at them in any detail, but I suspect that some of their contents will prove relevant to the OP's question.

Regards,
-- Al

Yeah, I already did the search - but when I did the exact same search I only get 7 results instead of 9. There's something odd about that.

Either way, we'd have to know the details to search for the original patents.

The search returns 9 results if you change the setting in the "search years" drop-down box from the default of "1976 to present" to "1790 to present." The default setting returns 7 results, as you found.

Regards,
-- Al