I posted this in the HD580 Appreciation thread also, sorry to those who have seen this twice.
I didn't find time to get out to get some blue tac for the mod, I worked 60 hours this week. About an hour ago I did cut some strips of electrical tape and applied them to the the inside of the cups covering the lower half of the metal screen to get the same effects as the blue tac would achieve. So far, the bass is MUCH punchier. It isn't overwhelming, but it brought back the darkness that the HD580 grills created. The sound stage is still very good, maybe just a tad smaller. The mids are nice, they're just a tiny bit closer and the highs are still clear, I can't hear any change there. I'm going to leave the tape there until I get some blue tac, I'm going to try to find some that's black so I can put it on the backside of the screen and it still not be noticeable. If you want your 580s to have a little more bass try this out!
And this is just a wallpaper I made for my iPhone 5 :D