I have a friend who used the capacitor of a defective electric fan and it worked. It looked like
this but I cannot remember the exact specs of the one that was used. It was 6 years ago and I didn't have PA background back then so I can barely recall the quality of the sound. All I can remember is that it worked longer than the typical, gold-colored capacitors we used. It might be worth a try, if not
try at your own risk.
If you can spend a little more it might be better if you just purchase an active crossover. Although I assume you know this already.