My apple supplied headphones when plugged into my macbook pro are exceedingly loud. Even at 2 bars, it's very loud. What's going on here? However, there are no issues with the volume on the macbook pro's internal speakers. 
A lot of earbud type headphones are low impedance. It's possible that the headphones you're using are low impedance and you might be better off with higher impedance headphones. You should be able to determine the impedance of particular headphones with a little research.
Any idea what the apple supplied ear buds are?
What "Apple supplied" earbuds? Earbuds don't come with the computers, only with the iPods.
Yes those, they came with my ipod. Anyone know what's going on with this? Can someone else say if their new 13" MBP does the same thing?
I have the new 13"MBP and I'm using the Apple earbuds that came with my new iPod Touch. When listening to iTunes I have to turn up the volume at least 75% on the Mac before it becomes unbearable. I have 2 pairs that work the same way. Everyone has a different comfort level in terms of hearing but if you say it's really loud at around 2 bars then your earbuds may be defective. Do you have any other headphones you can try? It shouldn't be that loud at such low settings.
Also, how is it when using your iPod? It should be about the same, if not then something else is wrong here.
My apple supplied headphones when plugged into my macbook pro are exceedingly loud. Even at 2 bars, it's very loud. What's going on here? However, there are no issues with the volume on the macbook pro's internal speakers.![]()