Sounds like you are pulling to many ohms from your head unit.
Any way to check if this is the problem?
95 SILVERADO EXT.CAB-5.7-175,000 AND STILL GOING-LOOKING FOR 5.3 SWAP
Yep. factory Delco 4x6 plates. 9.5 ohm
95 SILVERADO EXT.CAB-5.7-175,000 AND STILL GOING-LOOKING FOR 5.3 SWAP
Id say thats your problem. But just to see, use the positive off your left speaker and the negative off you right speaker and then run a wire from your left neg to your right positive and see if it produces sound for a longer amount of time without shutting off. With this set up you will be running at a higher impedence.
I'll tell you some more info...the speaker i'm talking about will produce sparks when the basket is touched to ground. Not always, but sometimes. I can remove the speaker, lay it on the seat, and it will play for as long as I want.
95 SILVERADO EXT.CAB-5.7-175,000 AND STILL GOING-LOOKING FOR 5.3 SWAP
Is it just one of the speakers or both and have you tried another aftermarket speaker to see if it do this?