At first I though it was in my head, and was a case of me "adjusting" to the sound of my headphones over the few minutes that they play. I decided to experiment, though, and started playing music through my 'phones earlier this evening and left them alone while I watched the Celtics game. When I came back, I immediately put them on my head, and they sounded fine, which seems to rule out the "adjusting" theory I had. Has anybody else experienced this?
I've never really seen this "phenomenon" discussed; certainly not as in-depth as the discussions regarding headphone burn-in.