firstly, what speaker is blown? the sub or the tweeter?
the best thing you can do to make a sub is to actually take the speaker out of the box it's currently in, and make a new box.
there are several designs that you can use, but the best box for your means is most likely a ported box.
basically it's a box sealed, with the exception of two holes, one hole is filed by the speaker, the other hole has a tube in it, the length and width of that tube dictates what frequency is predominant.
(yes, hard to believe but a simple plastic tube attached to a box can amplify specific frequencies, this means that as the frequency response of the driver rolls off the tube (port) can amplify the bass frequencies, meaning a standard driver that starts to roll off at perhaps 50Hz (not exactly bass), the lower frequiencies can be amplified perhaps down to 10Hz (-extra bassy).
I suggest that you have a look at a program called winISD
(also what speaer do you have -each speaker has theile-small parameters that dictate what it can and can't do it's frequency response etc). you can usually find that information from the googling a bit.
when you say tweeter, is it a dome tweeter? does it come apart (sometimes they are sealed).
if it comes apart it's a piece of cake to replace the voice coil
there's a place that sells new coils.
if it's the bass woofer part of the speaker that's blown, speakers can e re-conned, but honestly, unless you are talking about rare or vintage speakers, (like I currently have some original vintage g12's -guitarists will know, they are from the 70's) and I've repaired them because I want thm to be as original as possible...
however, if you're talking a fairly cheap speaker to start with, then you're probably better off buying a new driver.
hope that helps, I'm off to bed now, will post more in the morning if you want.
(I have a cottage industry building speakers and amplifiers in myspare time, and am more than glad to share this skill).