I know this thread is pretty dead but I picked a pair of these up in a trade not expecting much. Especially since I've previously owned the 500, 560, and HEXv1.
They came with what I believe are ori pads, and have since acquired the brainwavz angled pleather pads in which has really made these cans come to life.
Going from memory these cans definitely remind me of the 500's with the space of the HEX. I'm completely shocked by how good these are. Better bass response than the 560 and a lot less dry and hot in the treble than both the 500/560. If I were to rank these between the 3, I'd definitely put them second to the HEX.
They image better than the 500 and 560. More 3 dimensional in soundstage. A lot cleaner and clearer.
With the ori pads I really didn't care for the sound. Bass was flat, and everything up top was subdued.
For the last year I've been listening to the 58x. These 400s haven't left my head since acquiring them. I did spend hours doing A/B between the two and man are they different. They do have their trade offs.
I honestly feel I got the better deal in the trade. I did not like the dt990(600ohm) at all. The midrange was completely missing from the music. Definitely not my cup of tea lol.
Well , these are my initial thoughts on them. They are definitely staying put for now. Pleasantly surprised by how good these are.
Cheers!