Oh hay... we seriously always end up in the same threads. So I'll keep this short: lol, cables, voodoo .etc.
Back to the thread.
Today I recieved an HD650 via mail and I am quite delighted. I started of with Grados (bad) and got into mid AKGs... good stuff. So I basically had almost any mid and high-tier AKG can in existence, except the K1000. Then I sniped a broken HD600 and repaired it and was quite impressed with the results, but due to a minor driver dent the left driver was ~2db less loud and was annoying the crap out of me. So I sold it and with the additional bucks I earned from the repair and some spare cash I got myself an HD650. Why no HD600? Well Iliked them but the K240 Sextetts just had an edge in bass I was missing on my HD600.
When I plugged them in at first I laughed quite a bit... sound like the HD600 just a bit more expensive, meh. So I set them aside, let them burn and worked on a DIY-DAC.
So I finished and cleaned the place, checked the DAC and did some more listening...
While I don't believe (due to Till's efforts on the K701) in an excessive change of fr-due to burn-in, I still feel like the first several hours make them change a little.
Now, after only ~8h of burn in I don't feel like EQing anything. They sound quite neutral, which is why I bought them in the first place. From my experience, a slightly elevated (headphone) bass sounds flatter than a truely flat bass. This doesn't work for speakers... they'll just sound bassy this way.
All in all they are a keeper. Sextetts-mids and bass quantity, more extensions in both directions and less sharp treble. I guess I'll reduce my active cans to the HD650 the Sextetts and HF for on the move... the only downside of the HD650 so far is the bloated price, compared to some years ago.