The sub from my car that I fixed is also made of polypropylene and the contact cement seems to be holding up just fine. I think that prep is the most important part here. I used some 400 grit sand paper to rough up the surface and cleaned both surface with alcohol as well as a thorough hand washing. I know you want to fix and forget but realistically I don't see that happening. Since the original manufacturer could not get those results I don't suspect any layman can. Btw it was high strength hot glue from Stanley.
<a href="http://s75.photobucket.com/user/Socketman/media/PolkIntegraFront_zpsb78ed41f.jpg.html" target="_blank"><img src="http://i75.photobucket.com/albums/i319/Socketman/PolkIntegraFront_zpsb78ed41f.jpg" border="0" alt=" photo PolkIntegraFront_zpsb78ed41f.jpg"/></a>
Speaker I hot glued
How about
this looks interesting.
