Thanks. I'll leave them running on my old Sansa for the next few days.
After a couple of hours of use they started to open up a bit and sound quite good. The highs have smoothed out a little and aren't as edgy and the bass seems a bit more fleshed out.
All in all they're quite a good performer, especially on more modern music.
On acoustic stuff they don't quite do it for me, at least not yet.
And on a weird note: they sound somewhat "spatially limited", if I can say so, more akin to a closed headphone rather than an open headphone.
Soundstage size on its own is not bad, but the presentation is somewhat lacking.
The spatial cues and details are there but there seems to be something in the way, limiting this headphone from projecting a nice and focused image.
I suspect it has something to do with microdynamics and the speed of this drivers, which so far seem a bit compressed. Hopefully that will improve with burn in.