I have all 3 of these...I'll post some more detailed descriptions in a little bit but for comfort I would rank them.
1.Denon
2.Senns
...
3. AKG
For sound I would say
1. AKG
2. Senns
...
...
3.Denon
Alright, back with a full review of each.
I haven't listened to the Denons in a while, and my room mate is currently borrowing them, so I'll be going from memory on those, but I remember exactly what my problems with them were.
I'll start with them, in any case.
D-2000
First off, these are the most luxurious feeling headphones of the three. They are extraordinarily comfortable and if you're looking for headphones that will "WOW" your non-audiophile friends when they try them, these are definitely the ones. They look and feel the part of a high end peice of audio equipment. They are however quite delicate, and many people break theirs by dropping them from only a couple feet.
Unfortunately the sound quality, while very good, falls short of the other two. They have problems in the bass, mids, and treble. The bass is plentiful. Probably too plentiful, but that is a matter of taste. Unfortunately it's a bit out of control. Thick bass lines on recorded music lack detail and bass hits in electronic music tends to crowd out the mids. The mids themselves are mostly okay, but recessed. They have an almost 'scooped' sound to them. This brings the bass out even more, and unfortunately brings the highs out as well. The highs are where the D-2000s struggle the most. They are quite sibilant. Shockingly so for such a bass heavy headphone. Vocals sound flat out artificial on them. Vocals are where they suffer the most.
Because of the scooped sound they are very 'fun' headphones though. This makes them great for games with lots of explosions. It also makes them more impressive to less discerning ears. They do one thing quite well though, especially for a closed headphone. Imaging. Not sound staging, they tend to sound fairly close, but sounds are quite well seperated within a fairly narrow sound stage.
All in all they're a very good headphone, they just dont stand up to the other two sonically.
HD650
These sit comfortably in the middle in terms of out of the box comfort (more on what i mean by that in the AKG section). They have the tightest squeeze of the three, but thats never bothered me much (I wear glasses as well). The ear cups are soft Velour and feel nice on the ears. These have very solid construnction, much more so than the D2000 and the AKG. These are the ones I worry least about breaking.
Sonically they seem similar to the D2000 at first but the more you listen the more you realise how much more control these have over the bass and how much less irritating the treble is. The highest frequencies are definitely rolled off, which some dislike, but to me it leads to a more laid back listening experience. They're not nonexistant at all, it just sounds sortof like someone pulled a tweeter a little farther away. The bass is not nearly as thick as the D2000, however it is *much* more detailed. Subtle textures in recorded basslines are actually audible on these, unlike the the D2000.
Soundstage is not large, though it's slightly larger than the D2000. Imaging is rather poor on these, however (compared to the D2000 and AKG). It's been described as "blobby", in that you have 3 regions around the head where all sounds seem to eminate from, and I would say that's fairly accurate. The controlled lows and rolled off highs make these ideal for heavy metal though. If that is your genre of choice, these are the headphones to get. They relax the typically over present highs of poorly recorded distorted guitars while providing enough detail to let sounds filter through the distortion as they should.
AKG K701
These are my go to headphones for most things. They have a VERY light squeeze, so they don't bother glasses. The earcups are less soft than the others though. The light squeeze tends to keep that from being a problem however. The only comfort problem they have is that the headband across the top tends to have a very small contact patch with your head, pressing down into a small space on the very top. Without addressing this, it means that after an hour or so the top of your head will itch. This is pretty easily fixed by stuffing a couple socks up there, but its a nuisance that could've and should've been easily remedied.
Sonically these are the most articulate and detailed headphones I've heard. You will hear EVERYTHING. They don't have the bass extension of the other two, however they often fool you in that regard because the bass is so clearly seperated from other frequencies that it feels like the bass impact is quite strong. I like Bass, and I don't find it lacking in these at all. Highs are very present but not sibilant. They have some of the sparkliest clearest highs I've ever heard. If you do any sort of mixing or audio editing, these are the headphones to use. You will hear every problem in your mix clear as day. Because of this, DO NOT get these if you're main genre of music is heavy metal. For shits and giggles I just tried loading up Children of Bodom's "Follow the Reaper" and almost immediately had to turn it off because the buzzing guitars were flat out painful to listen to. Turning down the volume helps some, but metal is just better on the Sennheisers. Where these shine most is in the imaging and soundstaging. You're just surrounded by sound when wearing them. The soundstage is huge, imaging is everywhere, and distance and location are easily discernable through them. Anything with subtlety (and a lack of poorly recorded 'metal' guitars) sounds substantially better through this than either of the other two. For my ears it's honestly not even close.
One 'issue' with the K701 is that the performance is surprisingly highly dependent on how you place them on your head. I find that I get the best staging and imaging with the headphones pushed somewhat forward so the speaker center is nearer the front of my ear.
So to sum it up:
D-2000
+Extraordinarily Comfortable
+Has a very high feel to it
+Very fun sound
+Did i mention how comfortable it is?
-Boomy, unrefined bass
-sucked out mids
-sibilant highs
HD650
+Good comfort
+Nice, pleasing, relaxed sound
+Excellent Bass detail
-rolled off highs mean subtle details can be hard to hear
AKG K701
+Most detailed
+Incredibly revealing sound
+Comfortable when modded
+Largest sound stage
+Best imaging
-Odd ergonomic issues without 'sock mod'
-most natural way to put on head is not the best sonically.
-some less well recorded albums are nearly unlistenable at anything other than low volume
I'll be happy to answer any questions on those as well as the ATH M50, Ultimate Ears Triple.FI 10, and the Klipsch X10, as I have all of them close at hand and can do comparisons if you need.
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