Pros: Construction, Comfort, Sound stage, Bass
Cons: Not the most revealing or detailed headphone
I'm still a newbie in the headphone category, just starting to try out all the hyped ones like SRH840, HD650/600 etc from the beginning of this year.
Now I'm left with this, HD600, and DT880. I'm thinking which one of HD600 and DT880 to sell at the moment, so HD681 is certainly doing something right here.
In terms of absolute detail there's no contest here, HD681 looses, but for overall performance at such a laughable price, it's certainly a keeper.
Nothing wrong with the construction, plastic but yea, it feels solid on hand. A minor complaint that it's not foldable, but with semi open design this is not for outdoor use anyways.
Comfort wise I find them very suitable for long hours of use(especially with the velour pads replacement). To me they are just as comfy as both the HD600 and DT880.
Bass extends quite deep down there, quantity wise it's certainly boosted. I don't find it bleeding into the mids though. Certainly more bass heavy than HD600/DT880, but this makes HD681 more enjoyable for pop music. Due to the bass, I will categorize the overall sound as warm(definitely more so than HD600/DT880).
Mid does its job, don't find it recessed.
Treble is just the right amount for me, less bright than DT880 but sounds like a tad more in quantity than HD600.
Sound Stage is excellent for its price, certainly feels more 3D than HD600 to me
As for source, they sound just as good to me with xonar dg and audio gd 12.1, which make sense as it's not the most revealing headphone. Unlike the JVC S500, the HD681 does benefit from some minor amping, especially if you're going from a mobile source like ipod or mobile phone. Pairs well with bright sources IMO. A warm source/amp may make the bass too bloated.
Overall, well... Can't think of a better deal than this in recent head-fi gears, maybe the Sony MH1C...