Well, they're here, having come all the way from 1976 or so, by the look of them. Actually, after a good cleaning they should be just fine, although the wonderful skin-like original wrinkly fake leather on the earpads is almost all gone, just as it is on my Signet TK33.
No cat pee, though they do smell like they've belonged to somebody.
They're pretty much as I remember-- a little more bass than the SR-X Mk 2, but the bottom 2 octaves are weak. Channel balance is perfect. EQ brings up the bass but there's a limit beyond which even EQ won't help. I suspect Stax tensioned the diaphragms high to avoid nasty disasters when the phones were driven hard, which they seem to beg for. Highs are juuust verrrry slightly elevated, but smooth and flat. Strangely, the top of the top end seems rolled off, but that could be some old equipment that's still connected to the SRM-1 Mk 2 Pro. There's a lot more cleaning and swapping and general audio fussing to do before this is a fair test, but you can tell that these are 'phones that will let you hear everything that's on a recording, as long as it's above 80 Hz or so.
What was interesting was the comparison with the Stax electrets, the SR-30 Pro. Not as much difference as I expected. There's a broader hump in the mid treble as might be expected with the weightier diaphragm. You wouldn't want to crank these loud without some EQ to flatten those highs, but they're very pleasant and obviously from the same company that made the SR-X 12 years earlier. Significantly more bass from the 'trets too, and less of a closed-in feel.
Can my damped Yamaha YH-100s give either of these a run for their money? I intend to find out.
Haven't tried the Stax extension cable. Since I don't really need it I'll probably sell it to offset the cost of the 'phones. It's made of interesting materials-- the outer jacket feels like silicone rubber.