2001 Suburban LT audio trouble
 

Hi,
I have a 2001 Suburban LT. My factory audio head unit turns on and plays in all quadrants ie, LR, LF and so on. My issue is, only the tweeters are playing along with the sub in the back....which is distorted a bit. The head unit, amp, and all speakers are factory.Can anyone help me figure out where the problem is? I hope all those speakers are not blown. If the amp is blown, will it cause this issue? But then again i do not know if all the speakers go through the amp, or is it just the ones that are not working. Would be nice to have a Barnie style wiring diagram to see just how its all ran out. Thanks