I'm sure this has been asked before. How do you troubleshoot the system? I have a passenger rear speaker that cracks and a driver side rear that pops. Installed the oem aux adapter and don't get alot of sound out the doors speakers when I use my iPhone 4.
I've done the seatbelt thing and put stinger roadkill mat behind the rear speakers. Still the same. Can you Unhook the amp or not?
If it is the speakers, are there any replacement speakers(2ohm) that will work without too much wiring?
I have a 06 MCSC no nav or changer. Just the HK system.

 

Find an H/K amp that is known to be good. Swap yours for it and see if the problem goes away. If so, you will know that your H/K amp is doing what many of them eventually do - they die.

 

Got around to taking things apart and found the speaker cone coming apart.
Amazing what you can fix with a hot glue gun. No more cracking speaker. Probably a temp fix. With the cost of OEM H/K speakers or replacing an entire system. I'll take my chances it holds for awhile.