The Graham Slee ULDE amplifier that I'm borrowing from GS arrived a few days ago. First impressions with the T90... sounds pretty much the same as my vintage amplifier without the background hiss. Depending on your situation this will either be good news... or bad. The good is that it means that you don't need an expensive amplifier to get the most from the T90s. They're very easy to drive.
The bad news is that after I got over the 'new toy' phase I started noticing things that I didn't like about the Beyers.The bass isn't quite as tight as I like, the treble a bit boring(fortunately I didn't notice any of the sibilance others have reported), the soundstage sounds artifically large(has a weird sort of reverb like you're in a cave. The AT A900 had a similar coloration. It makes things sound lush and larger than life) and vocals in music can get a bit buried under the rest of the instruments when things get complex(though bass lines were still audible so the headphones were keeping up with the music just fine.) I thought that this meant that they weren't being sufficiently amped so I put off listening to them seriously until the GS arrived.
On a technical level they thrash my STAX SR-5s as I said earlier; but I find myself reaching for the STAX more often. The Beyers are more high definition; when vocals do take center stage they are downright impressive. The tonal balance is more pleasing and everything smoother. Maybe I have just grown used to it's slightly-grainy, bass-light sound? I suppose I am the kind of person that would rather reach for a VCR than a DVD; a cassette over a CD, an indie game over an AAA title. In summary the T90 reminds me very much of the Schiit Bifrost in tonal balance. Some will find it neutral and fall in love with it immediately; guys like me find it dull and boring. Once again I'm reminded that it's more important to find a tonal balance that you can live with than it is to find a good performer.
My impressions are the opposite of those who reviewed it earlier. I'm looking for less bass and more treble. Has Beyer modified these phones based on prior complaints? Or are our tastes in sound really that far apart? Just goes to show, you'll never know until you try something for yourself. Which unfortunately for those like me involves a lot of buying and selling.
Addon: Well, color me surprised. I decided to try these out of my rockbox'd Sansa Fuze to see just how 'easy to drive' they are. My portable AKG K81s sound a teeny bit underamped right out of the Fuze; the T90s sound fine. In fact the tonal balance is much more 'accurate'. My DAC and amplifier are both pretty warm(provides a good balance for the bright STAX), the Sansa is just a tad warmer than neutral. The Beyers sound great out of the Sansa; sure they could do with a better DAC but they don't need one like the STAXs do. I've tried running my STAXs with the Sansa as the source(using the vintage receivers as an amplifier of course.) It's not pretty. I'm wondering how these would sound out of my old Esscence STX now. I think there would be some synergy in that pairing. The T90s lose the veil with the Fuze, and I'm sure the STX would wake them up entirely. Don't get me wrong; the Fuze isn't an ideal pairing. I am noticing more sibilance and the bass is going to be underwhelming from a portable source; but it's better sounding than it has any right to be. Still it is better than with my home system and I'm getting chills down my spine with a few of the songs I've sampled so far, I almost wouldn't mind picking up one of the Tesla series designed for portable use. Volume wise the T90s take under 5db more than my K81s.