Sennheiser HD650 vs Denon AH-D5000

apples and oranges. open vs closed. you also did not mention the genre

IMO:

short-term w/o amping - D5000
long-term where you intend to grow the system around the cans - HD650

given my love for the 650's and claustrophobia the answer was rather simple

The faux leather will make you sweat a little, but now that i am used to it, not a problem anymore. Senn clamps a little hard on me, so i find d5000 fits more comfortable.

Depends on which previous headphone you are coming from, first time hearing the Senn hd650, i find the bass is really good. After hearing the d2000,and going back to hd650, i find the impact is lacking, but quality is better, less boomy. With markl-mod, the denons' bass do tight up a lot.

In the end, it depends which way u wanna go, mod the denon or settle with hd650. Personally i like hd650's bass slightly better than non-modded denon. Otherwise, i love the denon.

It's hard to compare the two as they are fairly different, one is closed while the other is opened. I have only owned the D5000's for a week while I have owned the HD650's for the last three year. But as of this moment, I will say that the HD650's are more natural and balanced (something that I did not really consider with the HD650's especially with the K701's around). The D5000's are too bass-heavy and sometimes bloated that it covers/muddies up the midrange which is why I did not feel that they are as balanced and natural sounding as the HD650's. To me, the K701's are too bass-light, totally opposite of the D5000's. The HD600/650's are almost in the middle offering fair amount of bass while remaining neutral. I have yet to find an amp that will fix this problem, as I have only tried the D5000's on my Heed CanAmp (I misplaced the 1/8" to 1/4" connector so I cannot use them with the SinglePower MPX3 amp for the time being). I will try them with the MPX3 and hope the D5000's will sound more balanced or find another amp that does otherwise I don't see much future in them.

For comfort, I guess the D5000's are most comfortable but they are a bit too loose for me. Sometimes I feel that they may slip out of my head if I move around or shake my head too much. The HD650's are very comfortable as well as they fit perfectly and sit securely on my head. I have the HD650's for three years now so the clamping issue is gone but I can understand why a number of of people complain about that issue with new pairs (my HD600's are new and they do clamp a bit more but nothing that makes them uncomfortable).

But if I have to pick one, I would pick the HD600's as they are a good compromise between the K701's and D5000's, which makes them perfect as all-around cans. The HD650's is a very close 2nd as they offer a more liquidity smooth sound with a slightly stronger bass but a tad bit less treble.

They are both excellent but I ended up keeping the D5000 for the totally engaging sound (if a bit bass heavy). I feel the HD650 is a bit more refined with details, slightly. I now own the D7000 and it provides the refinement needed over the D5000.
You'll enjoy either....or both ideally.

The question is what kind of sound are you looking for especially with what kind of music you listen to.

I will add that my new D7000's add some more detail/ refinement to the picture (over the D5000), getting them closer to the HD650 detail IMO. Still a very different signature though.
Shameless self promotion, I am selling my D5000's:
Denon AH-D5000 Headphones 3 months old FREE shipping - eBay (item 250462283881 end time Jul-17-09 14:33:49 PDT)

Sorry, I realized I stated the same damn thing in the thread above....don't drink and post!

Both are very good cans. D5000 is a easy listening headphone, and also easily to be matched for different type of amps. HD650 is a fantastic headphone, the sound is very unique and attractive. However, not most of people like this kind of sound; but if you like it, the sound is so musical and sweet. Only you may need to search for a good amp with best synergy.

D5000 is like the beer, and HD650 is like the wine.