
Well, some two years later I've got a ESS AMT-1 pair playing right now.
Yes, they are worth keeping. Holy hell, yes, they are worth keeping.
A pair turned up locally and I picked them up from the owner last night. Got them worked into the system tonight and I'm completely blown away. I built a pair of Verhagen's ribbons (
BKAA65 - Ribbon Loudspeakers) five years ago that I've just loved. Problem is that the ribbons fall off sharply below 700Hz or so. There's a little bass, but not much.
The ESS AMT-1s give me almost all of the ribbon magic, but with decent bass. The ribbons have a bigger radiating area and throw up a creepily real dipole soundfield that the AMT-1 doesn't quite have. But actually having bass with planar dipole goodness makes up for it.
The bass integration isn't perfect, but I've found a few remedies for that. I picked up a pair of modern 10" woofers people have found a good match for these. Also, I'm going to rebuild the crossovers with modern foil inductors and high-end caps. Then I'll line the cabinets with Dynamat and replace the stuffing. They need cosmetic work, too, but nothing too bad.
Still, they're awfully good stock. If anyone has a chance to grab a pair of these, I highly recommend them.