why does some of the songs playing on air1 sound so much better than when i dl them for sampling?

here's the two that concern me:
Jeremy Camp- Understand(album: stay)
Paul Coleman Trio- Run(album: new map of the world)

understand sounds like 3 doors down(slightly), run just sounds tight... BUT! dl them and they sound SOOO SLOW!

(a few minutes later)

you can screw what i said about jeremy camp- understand, i found the song i was looking for... damn my mouth for opening before my brain operates