Hello. I recently bought a used car and the sound system is not the best. I believe the left front speaker is blown, and sound is only coming from the right front speaker. There are aftermarket back deck speakers in place from the previous owner, however no sound comes from them either. How can I make the back speakers work? Or even tell if they are still playable? I bought new JVC component speakers but a user manual did not come with it and I have looked every where online to how to install them but I can't find anything. Help me out if you can, thanks!!