speakers
Hey guys I bought a MacBook Pro 13" in August 2011. I had the exact same problem. I would play a song on iTunes, it would sound great, then boom...cuts off no bass, and really low. Took it into the Apple store. They opened it up right in front of me. Low and behold, the tiny speaker connector was not all the way attached! Just a simple fix, and no problems thereafter. Just think how many of these they make a week. I would expect minor goofs.
Anyways, I hope you got your problems resolved, just thought I would share since it was relavent to this post. Thanks for everyone else that had advice. Its not very much fun when you buy a 1,200 laptop, and your ipad speaker sounds better....