Audio Systems: car stereo sytem, rca cables, generic guidance

Question
Hey mate
ive just installed 6x9 speakers, a xplod sub and amp 2 my car and after about 15 minutes of testing it out the sub crackled out...
it now doesnt work... went and saw someone about it and they think its the RCA cables or the head unit not being connected properly?? is this possible if so how do i go about fixing the problem?

Answer
Without knowing the make/model and year of the car, plus the make and model of the head unit, the sub amp, etc. I can give you only some generic guidance.

ONE:  The impedance of the speaker load on the amp outputs must be matched.  The impedance of the speaker may be higher than the rating of the amp, but not lower.  For example if the amplifier output is rated for 4 ohms you can have a 4 ohm or 8 ohm speaker connected no problem.  But, if the speaker is 2 ohms or if you have two 4 ohm speakers connected in parallel to one amp it will be a problem.

TWO:  Sometimes there are wiring problems that provide a short circuit to the car chassis; if the speaker is reverse wired it can cause the amp to go into protection or overload.

THREE:  The crackling out comment may have been the amp lost power. That could be due to a blown fuse in the car, a burned wire or the wire fell off its terminal. Check, with a voltmeter to make sure the amp has both 12v lines working properly.

If the amp is ON, but still no sound, disconnect the speakers and connect only one, stand-alone, known good speaker to test the amp output.  If it works that way then there is something wrong with the speaker or the wiring.

Cheers,
C