Thanks for the nice wellcome. I've been reading here a while, so it wasn't too hard to find the right words
I've picked the 990 (open) because the other two big beyers get much praise here and I don't like closed cans (like the 770). The 880 is semiopen, so I thought the 990 would fit better to me. I think appart from that there isn't much difference between them from a technical point of view. Only the "Pro" Line has the Diffusefield Equalization and the 3D Sound. The standard line should have the typical headphone sound instead.
The burn in also inproves the three dimensional appearance. I've got a nice CD from "Tekton Motor Corporation" called "Human Race Ignition". It's electronic music with samples of Williams F1 Cars driving around - a very nice CD to tests speakers and to annoy your neighbors
. With the K 501 the F1 Cars just boringly drive from the right ear to the left ear through your head. With the 990 Pro right out of the box the cars come from front left, drive to your right ear, then drive in 2cm distance around your head, and when they reach the left ear they disappear in the front left. This really impressed me, but after the burn in it gets even better. Now the cars come from front left, rush in 50 cm - 1m distance from the head to right behind you and then disappear in the distance. You now can even hear how they follow the track and drive to the front left again. To me there is not much difference to a good set of stereo speakers anymore.
Somehow I'm curious if the 770 Pro is also so realistic or if the 990 Pro benefits from the extra air it gets. I'm even more curious about the K 240 DF. It should have this 3D Soundstage and the lovely warm AKG coloration, but the damn thing has an impedance of 600 ?. So I need a decent amplifier first.
Oh well, I guess that's what they call the head-fi virus...