I have my twin 12' subs hooked up to my 600watt amp. A couple days ago I was driving and they were working fine. However, at one point, they simply cut out. I turned off my car and subsequently turned it back on but that hasn't fixed the problem. After getting out of my car to inspect it, I realized that when I turn on my car, the subs make a very low popping sound. I believe it may be the ground that may be bad as seeing that the amp still works, no fuses have blown and the connections seem to be right. Any help??