I just got these headphones today and I'm really enjoying them! A much more friendly signature to get used to than the AKG 701 and more lively than the Sennheiser HD650. I was worried that they would struggle to satisfy my bass-head needs coming from the Denon D7000 and VModa M80 (my current faves), but I loved them straight away. Yes less bassy but again it's pretty easy and quick to get used to.
I'm testing them in the office at the moment so not ideal but not terrible either, they leak but not as much as the Grados or AKGs I've owned before. Almost as comfy as the Denon D2000-7000 but don't get as hot because of the fabric as opposed to leather and semi-open construction.
I'm running them from the Yulong U100 DAC/amp at the moment and I think it works pretty well with that but I am eager to see how it goes with the Epiphany Acoustics EHP-O2D as it should give me some more warmth. The volume on the Yulong is at about 60%, the VModa M80's take less than 10% to sound loud, I have never had the Yulong up this high before, I expect that will be similar with the other DAC/amps, perhaps some of them will not cope with these headphones.
I tried running the headphones directly off my Samsung Galaxy S phone and it sounded good but way too quiet, about 50% of a reasonable level. I will steal the iPhone 4 off the wife tonight and test but I doubt it will be good enough. These phones take some driving, I knew that when I bought them and I am happy with that.
I guess the DT990 has been replaced by the T90? Just like the T70 replaced the DT770. If this logic is right (and I'm not sure it is, perhaps they are slightly higher models) then I wonder if we will see a T80 soon. Also I wonder if they will make 600ohm versions of these new Tesla models any more. Anyway, I am really happy with the DT880 600ohm and I just wanted to share my experience so far. I am going to write a full review for these headphones after my current batch of DACs (Yulong U100, Arcam rPAC, Audinst HUD-Mini), but I will come back and report a little on how they do in a less noisy environment soon.
Have a great long weekend everyone