[green_avanti]

There is somebody selling his RS1's and SSr225's because he does't listen to them anymore now he has his O2 setup?? What is this O2, it is headphones?

 

[boomana]

The O2 is the Stax SR-007, either MK1 or MK2 version. It's known as the Omega 2, since it "replaced" the original Omega, though some still prefer the Omega. It's an electrostatic headphone, and my personal favorite of the current Stax line when paired with the right amp and source. As for the set-up, the owner could be using a transformer box with a speaker amp, or any one of many dedicated amps, either from Stax or makers such as Headamp, SinglePower, Rudistor, or even DIY. A good O2 rig is a pretty wonderful listening experience.

EDIT: as G-Man mentioned, not cheap, but in the right rig, one of the best headphones around, and may be (lots of opinions on this front) the only great one still in production. I, myself, have varying opinions on the matter, since that this level so much depends on the whole system, and I certainly haven't heard everything in terms of uber-rigs, dynamic and/or estat.

 

[G-man]

Boomana forgot to mention one very important thing. An O2 setup is very expensive, thus the OP from the thread is commenting that he sometimes prefers the RS1 to the O2. (which is not unexpected since the grados are known for being brilliant with rock music) The O2 is one of the best headphones currently being produced, and one of the best ones out there.

 

[krmathis]

O2 (Omega 2) is short for the Stax SR-007. Which is the Stax SR-Omega successor, hence the Omega 2 name...