I own both the DT250-80 and the DT770 and have listened to both thoroughly. Both have their strengths and weakenesses; it largely depends on what you expect from a headphone. I slightly favor the DT770 as you will soon find out.
DT250-80s have the best sound unamped; they sound smooth with emphasis on midrange and bass; relaxed treble. Adding an amp doesn't change the sound much; they're comparably good unamped through a bad source as amped through a really sweet source such as the DVP-NS500V SACD player.
My complaints are they are not as comfortable as the DT770-250, have a slightly honky midrange (refer to the headroom frequency graphs and your own ear if you want to confirm this); voices sound "nasal"-ish. Otherwise if you like neutral sound are better than the 770s. Not as comfortable as the 770s and isolate a lot but not as much.
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DT770-250s are a great headphone if you give them at least a good (in my experience on par with the DVP-NS500V or greater) source. When in their ideal environment of amplification + good source, they have absolutely incredibly deep, accurate bass, a relaxed but present upper midrange, and really smooth, airy treble which I find very accurate.
The DT770-250s have INCREDIBLE soundstage; People have compared them to the AKG-501 which has one of the most accurate soundstages of any headphone. I think that the airy, fully-extended treble of the DT770s can be attributed to this.
If you're a real maniac and spend thousands on amps and sources, there is no debate: 770s rock in this sort of environment, although the 250s perform quite well too; you just can't get rid of that slight honkiness.
What if you have a bad source or no amp, or both? The 250s are an ideal choice. The 770s sound very sibilant, harsh, and excessively coloured in a low-qual environment while the 250s relaxed treble response and otherwise balanced sound mitigates the problems with bad source.
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I'd like to also state something about my past. I'm a very avid classical musician; I practice violin four hours a day in orchestra and solo environments (and yes, I'm only in high school). I use earplugs whenever possible and I am aware of the damage that occurs to musicians' hearing (110+ dB in full concert environments). I also delve into hard rock, performing improvisation with electric violin in a full rock band, using the same hearing protection as with classical music (I find that jam sessions are quieter than orchestra. Hard to believe but true.)
Also beware the DT770's "thickness" as stated by Todd of HeadRoom: I find that the overall presence of bass is too much on some recordings, such as the Dave Matthews Band's "Under the Table and Dreaming" CD which sounds better on the 250s than the 770s.
When A-B'ing the DT770s and DT250s to a live orchestral performance, I find that the DT770s reproduce the low end of an orchestral sound better than the DT250s, but have an edge of "digital" or "artificial"-ness to the high end. Perhaps this is due to the nature of the redbook recordings I use, or the fact that I own a RO Airhead which is famous for its graininess, or both. The DT250 is more natural but sounds WAY too limited, like someone turned the mids up too much and limited slightly the bottom end and definitely the top end. It still has a good warm sound though.
The DT770s do a way better job at accurately producing rock, hands-down. Why? When a guitarist with heavy distortion strums a chord and is properly amped, a huge mid-low bass resonance-type sound is produced with palm-muting in live environments. This is essential to the feeling of rock. While the DT250s make such a chord audible, it's as if it was edited out of the music on recordings, making rock sound horribly dry. The DT770s do a good job. If you're an audiophile that wants a neutral sound, you probably won't go for hard rock anyways; but the DT770s do the best job at this. The extreme treble air/detail does have some detriment to hard rock but is as overpresent as the DT250's treble is underpresent.
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In the end, it largely depends on your preferences when listening to music. The DT250 is closer to the sennhesier HD600 sound, while the DT770 I find reproduces other elements more accurately.
Let's have an A/B comparison of the following 'phone characterstics, in no particular order of importance:
1. Detail
Tie between the DT250-80 and DT770-250. The 770 reproduces more treble detail while the DT250 has a more detailed midrange.
2. Soundstage
Hands-down winner is the DT770; which has an ok soundstage with the worst possible sourcing/amping and only gets better as you improve components. DT250 has a very limited, "immediate" soundstage effect. Then again, if you hate soundstage the 250s are the hands-down winner
3. Frequency extension
The DT770 wins this one; both the low end and the high end are present in good recordings without being overbearing; although it's a fine line - some recordings display sibilance on the 770s or what approaches thick boominess.
4. Neutrality
DT250, hands-down. More neutral headphone frequency-response wise; most people would probably prefer the 250 to the 770 in its balance of sound.
5. Fatigue
The DT250 has less treble fatigue while the DT770 is more mellow-sounding with its smooth bass response. I'd say it's a close tie although I find my ears like the 770s better.
6. Comfort
The DT770 has bigger earcups and a slightly wider headband; I find that it is more comfortable than the DT250.
7. Scalability
The DT770 wins; the sound improves as you spend more on source, amp, interconnects.
8. Budget listening
Due to the ability to sound very good out of relatively horrid sources and going weakly-amped, the DT250 wins hands-down. I would cry if I had to use the 770s out of my soundcard's source but the 250s are ok.
So, there you have it. My detailed opinion.
I'd say this to sum it up: if you like the HD600 sennhesier sound, go for the DT250s. If you like the AKG501s but want bass, go DT770s.
Cheers,
Geek
