I have a set of AMT1c that I've rebuilt. I got 'em while in the Navy ~25 years ago. ESS is still alive, but only market in California, maybe only "out West."
They're killer speakers, IMHO, I love 'em. Quality of the sound, being subjective, will also net a few posts of "I hate 'em, they sound like crap" as well.
I bought 'em used for (I believe) $845.00 a side in the seventies.
The only hook with the ESS was that you had to have an amp with good power reserve to drive 'em. Yer basic $50.00 Marantz just didn't hack it. I used a McIntosh 6100 in (and after) the Navy, later a Mac 2125.
But, I love 'em, I'll probably be buried with 'em. They are among the best speakers I've ever listened to. The bonnets are getting kinda ratty, someday i'll make some new ones and re-laminated the bases.
ESS did have some pretty cool speakers that used plasma as a driver. The plasma was an absolute point-source, so the ambience created was amazing. If i'm remembering correctly, they went about $3500.00 a side.
I'm not surprised your dad is rebuilding 'em. I know a couple other folks that bought a pair in the seventies, and still work to keep 'em alive (the suspension rings were foam, and it "deteriorates").
FWIW
Scott
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