Audio Systems: noise feedback, mono amps, olds cutlass

Question
hey there i have a 92 olds cutlass surpreme i have jensen fold down deck p miller series 1500 watt mono channel amp and a bandpass box autobahn 2 12 iam not sure if my ground is bad or what but ill turn in off and the speackers just go nuts like it still on

Answer
Not much to go on there - your description of the symptoms are not clear and complete enough to give me strong clues.

So, I will guess. You can easily repair the grounds by pulling the ground wires off where they are connected to the chassis metal;  sand them down so the bare metal is shiny clean and bolt them down again.

Next, check the remote wire coming from the head unit to make sure it is giving a good 12v turn on voltage to the mono amps.  You can check this with your vom or voltmeter.

Next, check the wiring harness to the speakers; pull the plugs and reinsert them a couple of times to overcome any corrosion that may have crept into the terminal/pins.

Finally, if the amp is shutting off still it may be going into protection mode.  This is nearly always a short in one of the speaker lines OR a shorted voice coil in one of the speakers (from audio overdrive, you rascal).   If bad voice coil you can often hear them scraping inside the pole piece or the coil wires loose on the coil form.....

Happy hunting.