I just recently got a pair of HD-650's. I had an old pair of HD-600's from a friend, and the grills were dented. They were the older model, but I've always enjoyed them. In fact, through my journey of cans (I've gone all the way from SR-60's to LCD-2, HD-800s and tried every brand in between), I always found myself coming back to the HD-600s At least in my opinion, they do everything just right. They might not have the highs of some other headphones, but overall they do everything just what I want. I also have pretty finicky/sensitive ears, so a lot different sound signatures can irritate my them. But not the HD-6xx series.
So here we are, back to the HD-6xx's again. I recently decided to get a new pair considering that the 600's were pretty beat up over the years (previous owner doesn't know how to take care of things). I have to say, I really love the HD-650's sound. I was kind of worried based on all the comments I've read over the years about the 600 vs 650.
But honestly, I think they sound pretty damn similar, with the exception that the 650's sound warmer and a bit more lush. I actually understand more now why people prefer one over the other (now that I have both of them side by side to compare). But I'm really happy with my purchase, and think I prefer the HD-650s. I'll need to listen more before I make such judgments though. But given how sensitive my ears are, I do prefer the more laid back/warm silky sound (which some call veiled/muddy lol). Eh, such is subjectivity and listening preference.
Either way, I plan on keeping both. If I ever feel I need something a bit more livelier, I can just switch the 600 and if I feel I want more laid back/lush sound then I'll go back to the 650s. I also look forward to upscaling my set up around the 650. Do you guys have any suggestions for amps that are particularly good with the 650? EDIT: I'll make sure to use the search function and do research too. Just wanted to ask the current 650 owners what they think.