You can test each speaker from the multi-plug that connects in the back of the radio. An Ohm meter or any small portable radio and a 1/8" plug with the earphone cut off and the wires stripped can be hooked up to each pair of speaker wires.
Don't feel bad about all the off topic suggestions, I've found many people post without reading original or previous posts, often stating what has already been suggested.
Bob & Donna
'98 Gulf Stream Sun Voyager DP being pushed by a '00 Beetle TDI