One thing to consider. If you just replace one, for the sake of argument 4" driver, and not the other, it will change the sound of the one, while the other has its origional sound quality. You should replace drivers in pairs for that reason.
I have a pair of Boston Acoustics A120s that my cat use to love sitting on to look out the window. Needless to say, the 12" Passive Radiator was ruined ( I sure do miss that cat
) Right now, they sit in a closet, but I am looking at repairing them to use in another room. Two radiators are something like $80ish each.
You COULD stop by Radio Shack and see if they have anything you could use, or do a search on line for the size and impedence of speaker you need...
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