No air on acoustic guitars?
I don't agree, I think.
??
My references are the previous headphones I tried and own(ed) and with them in mind I don't find the guitars on the D5000's sound like cardboard at all.
Playing some Fado by Cristina Branco, acoustic songs by Sun Kil Moon I find the acoustic guitar to sound just like a acoustic guitar does.
???
But to be honest there's something in the sound of the D5000's that needs to get used to.
Both my Audio Technica's sound like headphones, when I am wearing them I am aware of it and there's this immediacy and exaggerated presence in their sound.
The D5000's seem to sound closed and more distant at first, their presence is more subtle, but very soon I forget about wearing them and the sound is just there, a lot quieter.
Another thing that I needed to get used to was their inconsistency in presence (and I mean this as a good thing) whether they sound upfront or more laid-back lies more in the recording than in the overall balance of the headphones.
My Audio Technica A500's have a tendency to sameness, treating everything the same way: upfront and with exaggerated separation and air between instruments in less complex material.
The D5000's can sound just as upfront, but only if the music is recorded that way, their ability to not alter spatial/acoustic 'information' make them sound more natural.
So yes, maybe there's less 'air' on guitars with certain recordings, but it certainly never sounds like carboard to me