Citizen's review . . . . .
Just wanted to say thanks for a great review. I really appreciated your ''recording" focused assessment and especially pointing out that the HE-400 can occasionally come across as accurate and realistic. That is spot on IMO. I needed about 2 weeks to really love mine. The "hit or miss" nature is really, if you take the time, a function in part of recording quality. Since I am the HE-400 "apologist" when it comes to that, I like to point it out.
Recording quality is all over the map (and I am not talking about bit-rates here), and imaging / staging fall apart to my ears, on occasion, when recordings really "pan" too hard to the right or left, or do something a little "unnatural" - like set drums to the left and a vocalist to the right and peg them there. That may be how the "stage" is arranged, and work well with speakers, but it isn't how I want it mixed for headphones! Stuff like that takes me right out of the moment and speeds up fatigue - not unlike having two people carry on conversations beside me and expecting me to somehow respond to both while a subway train comes to a halt in front of us. They HE-400s are also unforgiving, but for the most part, I feel they achieve a sense of realism and "fun" that is more often awesome than not.
I've not owned the HD-650s myself, but I have heard quite a few Sennheisers so I 'get' much of the appeal (comfort in fit and also sound quality). To me, however, most Senn's I've owned lack the speed and attack that really help get my attention and blood going. They were better for me as "background" phones and less successful when I really started listening critically and trying to search through the layers of sound. Also, while the midrange is great, they always trade off quite a bit of bass and treble energy for the sake of low-fatigue. Sometimes I just wanted more at both ends if you know what I mean! Anyway, the 650s have been out forever, and the main reason I've skipped them is that I think there are more interesting phones out for $500 these days.
I've been taking a break from the HE-400s and listening to Pioneer's BS-22s with subwoofer (I snapped a couple weeks ago). The imaging and midrange are so nice on them - vocals are always pegged to the center, and in front. My distance from the stage is literally my distance from the speaker - it is an uncanny and, to steal from a reviewer, "very seductive" effect. The treble is a tad laid-back for my taste, but they still retain great air and detail while seeming just a little warm with the sub working (sub is actually really good if a bit loose and boomy at around 40 hz). In effect, for $200 bucks all in, the Pioneers are highly satisfying. The main drawback is a lack of ultimate dynamic range - they go into compression somewhere around 90-100 dBs, so they don't get any "crank it" points, but at anything less than that they have the same awesome "effortlessness" of the HE-400s. They are the first speaker, of any type, I have ever owned, that I can listen to straight-up classical piano on without almost immediately sensing a timbre problem. Now that is a good speaker. Sadly, the HE-400s don't quite get there on the piano - there are some resonances / spikes in response in places I am not sure about that get in the way of a perfect performance. There is no question that I will be getting the Pioneer towers at some point - for about $250/pair they are a straight up giveaway to non-wealthy audiophiles like me.
Anyway, my plan is either to eventually sell the HE-400 and HD-595s I own for some 400i's, or I am going to migrate over to some Focal's. I've loved focal's car line and they have a very good phone out for a mere $300 - a good fit for my budget. Oppo also has some great planars coming out (don't know the price but they are a good young company). I just can't really spend a huge amount on phones with short warranties and a slight lack of development (mainly in fit and finish). Not when I can get a killer set of (5) speakers for practically the same price.