I want to say that out of the box, these hd600s are a bit more revealing than the hd650s and make hot recordings a little annoying to listen to. This is both a good and a bad thing. It is good because it will make me able to remaster some albums better than when using other cans as monitors. It is bad because hitting random play on foobar will not be as enjoyable and relaxing as when listening through the hd650s.
On good recordings like Patricia Barber's Premonition Years compilation, the hd600 blows the hd650 out of the water. There is just more presence to their sound, the instruments project with more authority and the detail in bass layering is much better on the hd600s even just out of the fiio e9. The hd650s in contrast make everything sound thicker and duller than the hd600s which makes them more forgiving of bad recordings.
These two headphones still sound like they are cut from the same cloth but the hd650s sound like they are EQ'd hd600s. I love them both! Take note I'm listening to the newer driver versions with the white material on the baffle which are reported to sound brighter and clearer than the older versions of these cans. I've had an older version hd580 before but they are not functioning anymore so there is no possibility of confirming the differences for myself.
The more I am getting used to the hd600 sound again, the more I tend to prefer listening to even the brighter recordings on them. I just feel like they are giving me a more faithful reproduction of the sound vs the hd650s.
If the hd600s still sound a little bright for me after some burn in, I might just be inclined to get an amp with a smooth sound signature for them like a Schiit Asgard or a Woo6. I think perfect amplifier matching for the hd600s will make me get the best of both worlds between the hd650 juicyness and the hd600 detail rolled into one.
The hd650 however will perhaps need balancing or a huge amount of power in an amplifier to pull off the trick in making them more nimble sounding ala HD600. I think the hd600 route may be a little less expensive to maximize so i'll stick with that plan.
I'm really sad that the hd600s were just recently discontinued. They are a really great pair of cans. In fact, they are my favorite headphones of all time.... Until... maybe when I get my hands on some Audeze? or high end stax? I don't know and don't want to go there yet
The 650s and 600s. The hd600s look better in person IMO. The Flash makes the marble finish look exaggerated.
My older HD600 pair. I used the stefan audio art equinox cables with them.
I might also get some aftermarket cables sometime but I'll get my final amp matching right first before tuning with some cables.
