Nice thread on two great cans. I have both, as well as the HD600's. All are fabulous cans IMO.
At home I listened to the HD800's exclusively for the last 3 or so months. What a wonderful pair of cans!
A few days back I resurrected my HD650's and boxed away the HD800's for a rest. For those who may think it's important, I use them with a Silver Dragon cable.
Anyway, the main problem I had transitioning from the HD800's to the HD650's was the bass. The HD800's bass reproduction is so much better. It's effortless, full and extended. With the HD650's, I was very conscious of the shortcomings in bass reproduction (less depth and space leading to a sort artificiality), but after a few hours this became less distracting and I could easily think the bass to be truly fine without having spent a lot of time with the HD800's. The HD650 is the 'darker' sounding of the two, but the word 'darker' tends to come with a negative connotation and this is not what I intend. They sound different in some ways, but very similar in some ways.
The point here is that I have no particular desire to go back to the HD800's at this time because I am very much enjoying the HD650 sound. I'll work with them for a while and then give the Ed8's their head time.
I'm having great fun switching between these three. Their differences are much appreciated since none are perfect and they each have their strengths.
The HD800's for me are strong in all areas and they're my hands down favourites. They're the ones I'd not wish to part with among the three. They're the only cans I've had that continue to amaze me even after an extended period of listening. Their spaciousness and ambiance are also grand traits of these cans.
Second comes the Ed8's, for their very interesting balance. The bass is so well represented with these cans and remarkably, without affecting the mids and highs as one would expect. They're also very clear and detailed. Their weakness for me goes with spaciousness of sound (not enough there). They're intimate because of their closed nature and the closeness of the drivers. Unfortunately, not all the time, such intimacy is what I'm looking for.
A close third comes the HD650's and for so much less in price. An incredible bang for the buck. A wonderful purchase IMO.
My HD600's are at work, taking away all listening time from my Grados. This one is special too and I keep changing my mind on whether or not I prefer them to the HD650's.