I warn you the sound isn't great but it's pretty good for an altoids tin. Besides, if it's quiet in your room it's good enough.
*Regular size altoids tin(1.76 oz)
*Headphones you won't want back(cheap ones)
*felt(for the inside of the tin)
*Scissors or other cutting tool(optional, but recommended)
*Foam adhesive(better and neater than tape)
Step 1: Headphone surgery
I finished this before the instructable, so I am showing you the finished version. You can get the idea either way. Hope it's not confusing. This is my first instructable so comment.