Vifa mid-woofer

Try Madisound or Parts Express.

http://www.oregondv.com/Vifa_Speakers_XT18WH09-08.htm

Does not seem available, at least at a casual check. Which speakers do you have? Most people don't know or care about drivers, but if you search by speaker brand you might be able to find a used one. Probably there are others who are in the same boat and will gladly sell you their remaining good speaker cheap. :) Good luck.

Thank you for your responses.I have emails into Madisound and Parts Express, although Madisound's site said it was not available.Oregondv already told me they no longer carry the woofer. The speakers are ACI(Audio Concepts Inc) Sapphire 25th Anniversary Edition.- Kevin

Maybe you can try digging out the specs of the old vifa XT18WH09 and try getting a vifa replacement that best match those specs. I bet it is just a revamp thing.
Hope this helps
Alexander