I don't know if the 2011 13" MacBook Pro is similar inside to the mid 2012 13" MPB, but about a year ago the sound of my mid 2012 MBP suddenly distorted and sounded as though the speaker had blown.
I did a search on YouTube and came across this video where a guy simply removed the back of the laptop and using an ear bud / cotton bud, put latex / rubber glue around the tear in the speaker. I didn't as much of the glue on as the guy in the video did. Just enough to cover the tear. This can be done without removing the speaker. Super easy!
A year later and the 'repair' still working OK. Granted, the sound is not as loud as it used to be, but it's OK and perfectly useable. I thought it was worth a try, nothing to lose. If it doesn't work, you still have to buy a new part. If it works, that's great! You've saved the trouble of buying and fitting the speaker system!!