Having sub & amp problems! Subs are making violent throbbing sound.?

I'd suspect that the amp is going into protect. Overcurrent, overvoltage, overheating, and shorted (or too low of an impedance for the amp to handle) outputs are the most likely causes. Check to see if the amp is going into protect.

If it is, first disconnect the subwoofers. If the amp then stays on, then you either have an impedance too low or one or more of the voice coils is/are shorted. If the amp continues to go into protect with the subwoofers disconnected, reconnect the subs and then disconnect the RCA's one at a time, checking to see if the amp goes into protect. If it now operates normally, then there's likely a ground or DC on the RCA. Change out the RCA's. If the amp still goes into protect, there's most likely an internal fault with the amp.

More information, please:

-Does this happen all the time? What about when the engine isn't running?
-Is the sub amp connected to an after-market head unit, or a factory radio?
-If it's a factory radio, what's the year and model of the vehicle?

It sounds like you are describing what's known as "motorboating" in an audio amp.
https://en.wikipedia.org/wiki/Motorboating_(electronics)


Try disconnecting the inputs first. If it stops, you likely need a ground isolation transformer inline with the inputs to the amp. eg. something like this:
http://www.ebay.co.uk/itm/Ground-Loop-Isolator-Suppressor-Noise-Filter-RCA-Amplifier-For-Car-Audio-Stereo-/272606832386


Other than that (or possibly as well), look for:
Bad power/ground connections,
Too thin cable supplying the amp [you need #4 or even #2 (25mm^2 - 35mm^2) or thicker for that power depending on length],
Bad battery (see if the voltage drops when the amp is on) or that general type of thing.

Also check there are no ground connections/shorts on the speaker wiring.

The final one is simply a faulty amp.


A 1200W amp is going to take well over 100 amps at full output; that needs massively thick cable to avoid voltage drops and will also very quickly *wreck* a normal car battery - it should be on its own battery, a "deep discharge" type rather than a starter battery, with a split charge unit to allow both batteries to charge from the alternator - or even fit a second alternator to handle the power.