I just bought these headphones and thought I should add my 2c to this thread. Keep in mind, I'm no expert...
It took me a little while to get used to these cans. My first mistake was that, due to the lack of bass, I had the volume up louder than I realised, which resulted in shrill highs. Honestly, no review could have prepared me for how the response drops off towards the bass. I was expecting the response to be perhaps like typical ESLs or something. ESLs tend to be bassy compared to these phones. One of the things I wanted to do with these phones is music production: trance and other electronica. I'm quite happy with a non-flat response for production, because it's not that hard to compensate if you know the signature of the equipment you're using. However, with virtually NO bass, it is very easy to get the levels wrong. These phones are NOT a good choice for production. I've tried using EQing to help use these for production, but the bass becomes cloudy if I amplify it.
In spite of what I've said above, I will not be returning them or on-selling them. What they do, they do VERY well. I listen to Bach and Vivaldi a lot, and they are SUPERB for baroque music. In fact, I think I will need some better recordings, because these phones betray some of the limitations of the recordings. I've listened to some Chesky stuff, and it sounds hyper-real. Vocals are also great, as are most acoustic recordings. I'm not a huge fan of pop, but most pop is produced to work on smaller systems, so the bass extends higher into the midrange. This means that the bass that is lacking on genres such as hard trance, are quite apparant. Alice deejay "better off alone" is a good example. RnB sounds good on them too. In fact, I would strongly disagree with those saying that rap is not good on them. I think these cans DO give a sense of intimacy with rap, but it's WITHIN a large soundstage. I don't listen to rap much...except for some nerdcore...but I like the effect.
One thing they have made me realise is how good my SPEAKERS were for the money. The clarity of the mids and highs on these are definitely better than my speakers, but only marginally. The separation is also better. If I could only keep one or the other, I would keep the speakers, because they are more versatile, but for SOME things, the ad900s are much more effective. The speakers in question are Event TR-8s. I paid less than AUD1000 IIRC.
I have these cans plugged into my Stanton RM-80 mixer, it's a low-end mixer, but it seems to be giving me a little more 'fullness' than my soundcard alone. The soundcard is an Audigy 2 Platinum, which was wonderful (and expensive) when I first got it, but is a bit passe these days. Still, it's better than any onboard sound I've heard to date.
My next pair of phones will probably be a closed pair and I will be looking primarily for flat response. I would still use the ATs for baroque and jazz and maybe a couple of other genres, and use the closed for trance and especially for production. After that, I'd like to try a pair of Stax, at which point the ATs may be surpassed.
Comfort-wise, I think these are great. They are incredibly lightweight for the size. I can see why some people find the "fat pad" mod necessary. I can feel the drivers pressing against my ears (and I don't have huge ears) but it doesn't bother me like I have found with some other phones. The 'wings' are a stroke of genius. ALL headphones should have something like this. The just fit to my head perfectly. They are nice and loose too, but don't threaten to fall off.
EDIT: I just realised that I have probably only ever heard orchestral, jazz, acoustic, and vocal stuff on ESLs, so my comparison above is possibly completely wrong. I'd be interested to hear some hard trance or something of that nature on ESLs and see how they stand up compared to the ad900s for bass intensive genres, then I'd be able to accurately re-evaluate my above statements.
