Jazz,
it depends on your reference point. if you are coming from harsh Grados or the V6, the DT880 may be perceived as rolled off. If you are coming from K340s and K501s, the DT880 highs may be perceived as brighter.
Within the frequency response curve, there has to be a hole somewhere. The DT880 is very neutral and balanced. People who are used to a midrange brightness, a la Audio Technicas, may find the DT880s to be lifeless and un-involving.
The DT880 is a "polite" headphone, and therefore may not have the excitement of the Audio Technicas, Sonys and Grados. The overall high end energy of the DT880, provided that the portion that pleases you most (say like triangles, bells and high hats), if it exists within the range of the hole, may make the headphone sound rolled off.
I likened the high end as "tube like" sounding, nice and smooth. Many people like an exagerrated high end, "sizzle" if you must, and therefore to them it may sound rolled off.
it all depends on the type of music being recorded or re-produced. I maintain that the DT880 is very NON-fatiguing, having a very large dynamic range, and warn of massive SPLs being created if one turns up the volume searching for that "sizzle" and impact. I find high end harshness to be very fatiguing (although the DT831 is one of my most favourite headphones, even beyond my DT931s). I likened the highend of the DT880 being somewhere between the DT831 and the DT931. Many people see both of those headphones as being very bright, and therefore see the DT880 as bright. I do not, I see the overall 'quality' of the high end, regardless of the energy levels.
The overall sound quality of the midrange to highend is more balanced in the DT880. (IMO). Many people are not used to that balance. Which is why I maintain that its closest competitor is the HD600. The HD600 sounds rolled off to some people. To me, I perceive a 'veil', a flange. The DT880 does not exhibit that propensity. Its midrange is, according to Greg, sloping downward. This slope could be perceived as a roll off of energy. So people will crank up the volume to compensate and therefore increase the SPLs. Somewhere along the line the perception of midrange slope turns into perceived high end roll off. So they again crank up the volume, not noticing that their attention has shifted.
Even Beyer and Jan liken the DT880 to being in the Dt770 and Dt990 class. I maintain that they are in the DT831 and DT931 class. Chances are that it lies directly between both classes. Some say that the DT770 doesn't have a fast high end, while others say that it does. They point to component sources as being the culprit. I say that they are both right, just using different terms. To wit, the DT770 sounds, (to me), as being mid-bass bloated (especially in the lower vocal range. I say somewhere around 200 Hertz), and therefore the OVERALL quality of the sound tends to sound dark. To someone else, who just listens to the high end, and not the overall balance, the high end is perceived as being all there. The same problem exists in describing all headphones.
So while the OVERALL balance of the DT880 is "natural" and smooth and flowing, in COMPARISON to other headphones, which exaggerate some part of the frequency response curve (lower bass and upper highs in the Grados, upper mids in the Audio Technicas, and lower highs in the DT831), the DT880 may sound (at least to me it does) rolled off in the high end.
But if you listen to the DT880 for hours at a time, and then change over to any other headphone, you may find that it takes a LOT of getting used to. It's not the overall sound, but rather the lack of dynamics perceived, the relative sound levels between the instruments, and of the instruments, which causes immediate fatigue. Other headphones in comparison sound "compressed". Some people may therefore perceive the other headphone as being more lively, when in fact they are not.
Then there is the matter of soundstage. Make no mistake about it, the DT880 has a w-i-d-e soundstage. This wide soundstage again contributes to a false sense of lack of high end energy. Why? Because you hear each instrument more clearly. This lack of compression in a horizontal plane, gives the illusion of a lack of dynamics, of volume level. We expect the sound to be compressed within a 120 degree field. As it widens to about 180 degrees, the overall perception is one of a lack of volume. It is not. But the distance between the instruments, and the greater time to perceive sound bouncing from one end to another, or the merging of tones, seems stretched out. This again may be perceived as being rolled off, of being slightly smudge in imaging. It is really quite the opposite; it is imparting a space for the music to breathe. And in that space, the dynamic range is also greater, but this time in a horizontal plane.
And just as soundstage encompases the height and width and depth, so also you'll be able to hear "deeper" into a recording. It's that dynamic range again, that uncompressed feeling of giving "weight" to a performance. The the overall sound of the DT880 therefore sounds "more open" and "airey". This perceived blast of fresh aire, this unconstrained sense of sound, is opposite to the constricted sound of "busy" and "cramped" that most people are used to. It can therefore be perceived as being "rolled off".
With a judicious hand on the controlls, I feel that the resulting recording will sound fantastic on the DT880, but may sound lifeless on more forward, brighter, or exaggerated headphones. This lack of "life", or "impact," sensed on other headphones may necessitate the turning up of volume, and with it, the increase of distortion. With the increase of volume, the volume limiter threshold may be reached. And a high end roll off may be perceived.
Then again, it may sound too bright or too forward, if the mixer compensated to the point where he reached both the compression and volume limiter thresholds.
It all depneds on exactly what frequency (instrument) is being bought to the foreground.
I hope I have clarified my position, and hopefully you have a better understanding of what I am saying. It is just a difference of perception (linguistic symmantics).
