I just checked and the speaker wire is connected to the lower terminal on both speakers. Since one of the speakers works perfectly fine, I would think the issue might be inside the speaker. When I get back from church, I will probably try to pull the woofer out and see if a wire is loose.

Another thing I thought about doing is taking the speaker wire off of the banana plug and connecting it directly to the terminal. Not sure if that will work but it might be worth a shot.