Am I a bit late to the Party? Nevertheless, here's my T90 Journey.
Always been a Beyer man, started with the old 770'250 in 2002. I must have had the DT880 at least 3 times, the last one, the 600 ohm Edition, has been my workhorse and reference for more than a decade. Never liked the Teslas though. There was a P "something" at a meet 2014, and my friend has the T1. Technically fantastic, but way too much detail and no musicality. Reminded my of the HD800 which I
very much dislike. Have they all gone crazy?
In late 2022, I stumbled upon a broken T90 in digusting state and one broken driver. It was cheap. Ordered a new system and waited for the postman. It arrived and was in such bad state that I made a complete disassambly and put frame and cups into the dishwasher. Did not help much, most of the dirt turned out to be glue. Put one cup into hot water and ripped the out aluminium ring off to get the grille textile out and thorougly cleaned. Now to the systems. They turned out not to be T90 systems. So I had one new T90 system and some other Tesla driver which measured 237 ohms. Oh no...That was the point when I got really angry with myself, so I put everything into a project box and left it there for one year.
Last christmas, I allowed myself to buy the remainder, headband pad, new pads and of course the 2nd driver. Put it together and started listening.
It was horrible. There was really insane treble, and something wrong about all of the attack & decay. As if the music was played faster, all sounds were too short. A
boooom was
'bom, a
zzzzing was reduced to a
zink. They have definetely gone crazy...but wait, Beyer recommends using them on their own amps, which infamously have an output impedence of 100 ohms...
Ended up soldering a step by step adapter from 0 up to 100 ohms. When I got past 50 ohms, things started softening, especially the hot treble and the nutty PRAT. Soon stepped up to (the recommended) 100 ohm value. And then I sat there, just listening, listening, listening. That was the best I have ever heard from a HP. If the HD800 had sounded like that, I would have instantly started putting money aside. And that at a time, when my most expensive HP was 250ish €.
The T90 becomes a totally different HP when driven with a 100 ohm adapter. It's lush, fluid and musical, with the nicest mids, well textured and impactful bass, and the highs are there in an enjoyable way. And it is very detailed, I would not have thought that my DT880'600 has missed out so much micro details.
A word to the pads. I have dozens of pads in my tinker inventory, e.g. 880, 770, T1, diverse AKGs, Sonys at AT, and even some DIY stuff or modified china stuff. Forget all that. IMO, the T90 sounds best with the stock pads. Everything else sounds, at best, 80%, so you end up with an okayish sounding headphone. They are not listed any more in the (germany only) online spare parts shop, but you can order them with the Part No. 911348. Examples:
EDT 90 (Germany) or
EDT 90 (Australia). I have ordered 3 additional pairs, as I intend to get old with that thing.