I received my 8-wire Copper Venom for HD800 about 10 days ago.
In one word: AMAZING!!
HD800's are notoriously bright. And I'm pairing them with Gungnir/Mjolnir stack which is also on bright side of neutral.
So, naturally, I expected the combination to be too bright. I figured I would just have to live with it until I could soon upgrade to a better amp/dac.
Surprisingly, I do not find the combo to be too bright at all.
The treble is well extended, but not harsh. And it's very very clean.
Nobody ever complains about HD650 being harsh, but compared to my HD800/Copper Venom combo, my HD650's treble sounds more grainy and less clean.
The cable also manages HD800's bass very well.
HD800's bass can be a bit lean with a wrong system and/or cable.
The bass on my cans is plentiful. But what amazes me is the quality of this bass. I can clearly hear the texture of every bass note. Impressive!!
Soundstage, as you all know, is one of HD800's strong points.
It feels like the stage is in front of me, very wide and deep.
In comparison, soundstage of HD650 is more two dimensional, wide enough but not deep. It feels like I am on the stage with the performers (which can be a good thing, if I'm listening to intimate jazz music, for example)
I have never owned an HD800 before. All my impressions are based on what I remember hearing other HD800s in different systems in different environments, so please take my impressions with huge amount of salt, YMMV, IMHO, and all other caveats.
All I know is that I'm glad I purchased the Copper Venom. I was worried that I would need to upgrade my amp/dac immediately due to bad synergy. Now I know I don't have to.
Will I upgrade my amp/dac in the future? Probably, this is head-fi after all
But when I do, I will blame it on upgrade-itis, and not because of bad synergy.
My HD800/Copper Venom, however, are not going anywhere