Amp isn't getting any power

I have a Kenwood 1000watt amp hooked up to 2 12" MTX subwoofers in my car. Just recently, the subs stopped working almost completely. Occasionally after the can has been off for a while, they'll work for a few seconds but then shut off again. I've checked the voltage on the wires with the car off, and everything is fine. But when I turn the car on, the voltage slows to a trickle. I've checked the fuses and connections, everything seems fine. What in my car could be draining all of the power when i turn it on? Everything worked fine until a little while ago. Any help is appreciated.

what is the impedance load on the speaker output of the amp ? How do you have the subs wired (parallel, series, .. ) ? You may have too low of an impedance and damaged the amp or the subs.

I'm assuming you have your power wire from the amp hooked directly to the battery, and a suitable ground ?

And by reading your post, Im gathering your voltage drops once teh car is started ? What does it read before starting, and what does it trickle down too ? Have you tried measuring the voltage AT the battery and seeing what type of behavior it exibits?

that problem because of low power , you should contact to any expert to check out th whole system.