I'd like to see Siegfried Linkwitz and E.W. Kellogg on the list, along with Alan Dower Blumlein.
Blumlein took out the first patent (in 1931) relating to stereophony. His was the idea of carrying two channels in one groove by using each wall for a channel and the stereo cartridge, stereo cutter head and coincident velocity microphones in the crossed figure of eight configuration all were covered by this patent.
To quote from the Wikipedia entry
http://en.wikipedia.org/wiki/Alan_Blumlein "... Blumlein was so central to the development of H2S (airborne radar to aid the bomb targeting) that when he was killed, 1942, on a test flight many believed that the project would fail. But it survived and was a major factor in shortening World War II. Blumlein's role in the project was a closely guarded secret at the time, with his death not being announced for a week. ..."
He also attended the birth of EMI in 1931 (he was employed by them) and made significant contributions to the design of television systems.
I'd say he ranks ahead of the fellow who designed the SME tonearm.
As to Kellogg, he seems to have invented the electrostatic speaker in 1929 and had a hand in moving coil and paper cone speaker design as used in the original Voice of the Theater speaker of 1925:
http://history.sandiego.edu/GEN/recording/loudspeaker.html
