Pros: Timing, punch, stage, bass, balanced yet forgiving, manufacturing quality
Cons: too mellow, highs could have more bite, too small, the fit is not for everyone
I don´t understand why so many people don´t like these headphones. And IF they are loved by some people even then the descriptions of its sound differs so much that I always wonder if people were actually listening to the same headphone. I can only say that I loved them right out of the box on my portable player: the bass really goes deep (and I mean deep bass frequencies from 30-80 Hz) but does so without being pretentious, frequencies around 90-150 Hz have punch (but not that much "weight"), the lower mids are very warm and everything else above is very balanced yet a bit smoothed. Female voices are sounding fantastic, they have a body and a chest without being overtly pronounced. Compared to the Superlux HD-668 the pronounciation sucks but the presence area and upper mids are more balanced.
The highs are a bit problematic though: they lack bite and detail. Precision is good but celesta and strings loose gloss, brass looses its bite. Combined with the mellow lower mids the sound gets too warm, it sounds like the music is cuddled into a nice warm blanket. Furthermore I assume that the mellow lower mids are revealing the resonance frequency of the housing, there is an effect that can best be described as some kind of "distortion" which is present even on lower volumes. In short, lower mids are sounding a bit plasticky.
But: despite the fact that the mellowness & the missing bite are present the overall sound is quite balanced, you´ll like this headphone more and more the longer you listen to it because even with this mellow sound it manages to show bows striking strings without sounding artificial. Doing an unfair comparison to my HD-600 I prefer the bass of the HD-448; it goes deeper, has more punch and better timing (the precision on the HD-600 is superior though). The HD-448 is definitely faster than the HD-600 up to 2000 Hz or so. Then the much higher resolution of the HD-600 kicks in.
Furthermore, I was extremely baffled by the staging and the room response - for a closed headphone its marvellous: it is wide and fairly deep. Closely miked instruments can be observed with their own reverberation and room, yet it still is able to present the room response of the whole ensemble. This is an art I have not observed in many headphones yet.
I assume that my description sounds different to anyone elses'. The reason is actually very simple: since this is a closed headphone its sound depends on how you wear them, in order for them to sound good they need to seal! If your earlobes are big, your head too small or you have too much hair they cannot seal the air and they WILL sound thin, aggressive & without bass. My head is a bit bigger than usual and my earlobes are really tiny which has the result that they fit perfectly for me. Which is the reason that they are not for everyone, they simply are designed too small to fit everyone perfectly.
The design: on photos they look cheap. In reality they don´t look that cheap but still not that sophisticated, their price range is apparent. But once you actually touch them your opinion will be reversed because they are manufactured so nicely. Everything fits and feels good. My head doesn´t sweat even though the cushions are not made out of velour, I can wear them for long hours and nothing hurts.
All in all they are really very pleasant to listen to. If you like pronounced highs you have to search elsewhere, if you like your sound to be very direct and aggressive (á la Grado) you also have to search elsewhere. But if you like to listen to a warm, mellow yet balanced sound with a very good room response and staging combined with a deep reaching bass that isn´t bragging these headphones are for you.
Please note: My description of their sound was done using the Xonar Essence ST. On my Sansa Clip+ (they are engineered to be used on portables in the end) they actually sound a bit better: the thin and grainy sound of the Sansa tremendously helps these headphone getting a bit more aggressive and leaner.