Stax Lamda Pro Earspeakers

These headphones are in great condition given that they are vintage.  Other sellers have often noted that the foam on the inside of their headphones is worn down and degraded.  Not so here.  I got these along with the SRM-1/MK2 after upgrading from the 2170 system and noticed a big difference in quality.

For sale are the Lamda Pro headphones only.

See Ken Rockwell's review below:

These Stax SR-Lambda Professional electrostatic headphones
are the most perfect audio transducer I have ever heard, and I've grown
up around daily music performance, the Quad ESL, Quad ESL-63 and
B&W 801s.

The sound from these Lambda Pros is simply extraordinary. It
is natural, clean, open, delicate, powerful, detailed, precise and
revealing, all at the same time.

Stax electrostatic headphones win on subtlety. (Stax'
marketing people have always called these "earspeakers" instead of
headphones.) If you want to enjoy every nuance of your music across
hours and hours of careful listening, these are your headphones. If you
prefer something that boosts everything for a screeching 30-second demo
spin, these aren't for you, although they do go extremely loud.

There is no distortion. Every instrument, voice and
multitrack layer is heard distinctly, never mushed into anything else.
Instead of loud walls of crud, one hears everything separately,
regardless of how loud you enjoy your music.

Listening with these headphones, all the distortion and
coloration of conventional speakers and headphones is stripped away,
leaving only pure music. I hear no distortion at any level.

If choral masterpieces are your thing, you know these are up
your alley, and likewise, if Metallica and Aerosmith are for you, you
may for the first time hear every one of the hundreds of mixed,
deliberately distorted sound layers individually. You can separate
every voice in the chorus, and hear distinctly every one of the hundreds
of layers of sound added in multitrack recording.

Whatever distortion was in the guitar amp is all you're getting; you won't get any more by turning up these headphones.

These are thirty years old, and way outperform brand-new conventional dynamic headphones like the Sennheiser HD 800 and Ultrasone Edition 8 in every way.

These Stax headphones excel because they are electrostatic, which have numerous advantages over conventional headphones like most Sennheiser, Ultrasone, Beyer, Grado and AKG.

Unlike electrostatic speakers, these headphones play LOUD,
easily hitting 118 dB SPL without distortion. They are rated at 0.007%
distortion at 400 Hz at 100 DB SPL, which is live concert level. The
sound quality is spectacular, and they crank out more sound than I'd ever want.

These headphones work only with Stax' dedicated amplifiers or adapters. The Stax SRM-1/MK-2 Professional amplifier, for example, was introduced in 1982 along with these headphones.

"Professional" means that these electrostatic headphones use
a larger spacing between their electrodes, and use a higher polarizing
voltage (580 V instead of 230 V) so that these headphones have a huge
maximum output level, especially at low frequencies.

These Lambda Professionals and the SRM-1/MK-2 Professional
amplifier were developed at the request of Mercedes-Benz, who asked
Stax to develop a high-output version of the regular SR-Lambda (not Pro)
that had been introduced in 1979. Mercedes-Benz needed a transducer
that could reproduce extreme subsonic information loudly to help them
reproduce the sounds of automobiles for design and analysis.

These Stax Lambda Professionals were the world's top
headphones from their introduction in 1982 through 1995, when they were
replaced by the similar Stax Lambda-Novas.

A reader's dad worked at Capitol Records,
where the Stax Lambda Pros had been used for years. Capitol stopped
using them around 2001, and threw them all away! That reader's dad
grabbed a set from the trash along with the amplifier, and is still
enjoying them to this day. Capitol downgraded to ordinary Sony
headphones for the same reason they use Yamaha NS10s: to be
sure mixes sound good on ordinary equipment, not just on the very best
equipment. Popular music is done this way, while classical music is
still done with the best monitors. (In practice, everyone checks their
mixes on all sorts of gear to be sure it will sound great everywhere,
and mastering is always done very carefully.)