The standard test is to use a battery, and touch the contacts to the +\- of the speaker wire. If all they speakers jump, they are most likely ok. I like to gently pressing on the cones about 1cm to feel and listen for the voice coils rubbing as well. They should move freely. If you have acces to a multimeter you can check the impedance as well. If you don't read about 4 ohms, you might have an issue. I believe each individual drivers are 16 ohms apiece.
Last edited by lokikallas : 09-16-2013 at 12:12 AM.