After building a very exotic valve headphone amp, with a Sophia Mesh Plate Rec. tube, I wanted to match this thermionic marvel with REAL quality phones. I have a pair of AT ATH700 Airs which I love and think excellent value for $160. I also have my "train" pair of Phiaton 400s with their closed back. The Phiatons are good but the ATs much better. I Googled for the "best headphones" the the answer came back "Sennheiser HD700s". Too many good reviews to ignore them and at around the $1K mark I must have a pair. RRP for these pro. phones is $1,100. Even on eBay they were going for $1,050. But shopping about I picked up an authentic new pair for $750. At $750 these are a steel. I'd pay $750 just for the foam padded box they came in. The HD700s are made in Germany and feel solid and very profession. And that's just how they sound. Rated 150ohms and 105db efficient these are easy to drive phones.
 
But lets talk about the sound. Firstly the bass is very extended but far from overblown like so many cheaper phones can be. Bass is very articulated and no problems following a slap bass (doubled bass) being played with gusto. You can hear inside the bass and the air around it. Mids are linear, clean and harmonically rich particularly through the valve HP amp. I could understand if some think them a little dry because they really add nothing to the mids where some might want extra weight here. Treble is balanced and not over bright and sibilance is controlled but not overly so. They may be a tough too much "sshhh" and not so much "S". Again a different amp may offer a different balance.
 
I would thoroughly recommend the Sennheiser HD700 even if you pay full price. These phones are keepers for the at home serious listener. To achieve the very best from them match them a high quality amp\driver and play REAL music through them not compressed mp3 sound files. These phones are why we listen to music the way we do.

While having a listening session with a friend on my newly made valve headphone amp we swapped phones. I was using the Audio-technica ATH700 Air and my friend The Sennheiser HD598s. My tube amp can drive two HPs at the same time with both being close to each other in impedance and efficiency. For the extra $100 over the cost of the AT I would say the Sennheiser are good value. They were not as bassy but good bass extension and mids and treble was airier and cleaner. By no means are the AT a slouch and for $160 they are really excellent value. But if you want something better and happy to pay around $100 more I would suggest the Sennheisers.