Help needed with car audio

Hello all,

I’m trying to figure out what is wrong with my audio system. I have 4 high end speakers and amp but I’m getting terrible sound, it’s really harsh. 1 or 2 weeks it sounded amazing, but then suddenly sounded harsh and painful while I did not change anything.

Small question, 1 thing I noted was that I saw that the ground point has 0.003 ohm resistance. But when I turn the car on and measure the same point (ground point and battery -) the resistance turns up to 36 ohms and when I turn the car off, then for 5 minutes it’s 8 ohm and then slowly going to 0.003 ohm again. My question is: does this mean it’s bad ground or is something else going on? Can bad ground affect the sound like I just mentioned?

Thank you for your help all!