That's what I was about to say, it sounds like connection to me. If all else fails, run it on a home stereo with a known good wire. If it runs without distortion, your speaker is probably fine. Press on the back of the cone (even pressure on both sides, and not hard) and look and make sure the dampener is moving and contracting properly. When you do that, listen for a scratching sound. If the speaker plays without distortion, the dampener moves and contracts properly, and the voice coil doesn't make a scratching sound when you move the cone by hand, They're fine and it's most likely wiring shorting out or a connection coming loose.