I have a '99 318i and have crackling/popping front speakers only. I've read a lot of other posts saying it can be a ground loop issue so I tested the grounds on the both driver and passenger side (below the plastic/carpet foot guard) to see the difference in ohm reading to ground. On the passenger side I got 0.5 ohms on all the wires yet on the driver side I got 0.1 ohms on all the wires. I don't know where to go from there. Where's the next grounding points I could check or what could be wrong? Its just a basic 6 speaker system with no aftermarket amps just a new head unit I put in. I also know its not a blown speaker because I changed with with the back speakers and same thing of front not working and back play just fine. Any help will be appreciated.