Pros: Effortless detail and musical insight. Wide sound stage. Slight treble lift helps old folk like me. Revealing.
Cons: Awful with bright sources. Needs a proper headphone amp.
When I first unpacked the DT990s I plugged them into a rather good Ruark radio playing on my desk. The result was an absolutely awful, screechy performance. Having recovered from the shock I remembered that I had boosted the treble on the Ruark to make speech clearer. Several reviewers say the DT990s are screechy but that really is a source problem. They do have a slight treble lift and reveal the source exceptionally well, so if the source is bright, they will let you know!
Plugged into my best sources, a Benchmark DAC2 and a Beresford Caiman 2, they are absolutely fabulous. I listen mainly to classical and jazz and these allow an effortless insight to the performance with nothing masked or recessed. The soundstage is as good as I have ever heard from headphones and you can 'see' every instrument effortlessly. They are very slightly bright but that is not a problem to me and they don't cause listener fatigue. They do not make good sources screechy and they don't create exaggerated sibilance. What they do do, is remind those of us with older ears what we used to be able to hear more clearly (I can still hear up to 17 kHz but probably at a reduced level). If you have teenage ears, maybe they will sound too bright?
For comparison, to my ears, my Shure SE535 IEMs are the most accurate, neutral 'phones I have ever heard. The DT990's slight treble lift makes them more enjoyable and more revealing for me.
They are certainly not intended for portable use but.....
My AK Jr will drive them but you need the volume up to 90% and the AK Jr completely loses the subtlety that it usually delivers. Certainly not a recommended combination.
My FiiO X5's volume also needs to be around 90%. It sounds like an effort but it retains some of the quality audible with easier headphones. Again, not a recommended combination.
My FiiO X1 virtually gives up, and I don't blame it, it was silly to have tried it.
Good though the AK Jr and the FiiO X5 are, they are not remotely as good as the Benchmark DAC2 (nor the Caiman) and I would not dream of using a portable device at home with these headphones. If you don't have a good home headphone amp you really should try one. The difference with these excellent DT990 headphones between the FiiO X5 and the Benchmark DAC2 is enormous. You can hear the music with either portable player but with the DAC2 you can hear the performance. It is the difference between, "that's nice" and "WOW!"
Back to the DT990s - the comfort is pretty good. I can wear them for an hour at a time without worry but I can't say that I ever become unaware of them. Unlike closed back 'phones, lifting them slightly away from your ears makes no difference to the sound quality so a bit of careful stretching of the head-band may be all it takes to make them more comfortable. The weight is barely noticeable but I would prefer a bit of extra padding on the top of my head. I do find myself fiddling with them every few minutes.
Design-wise, they are functional. They don't look fashionable, they look functional. The manufacturing cost went into function rather than fashion - thank goodness.
Value for money - I only paid £102 and they are easily worth that.