Hi I recently upgrade my entire 2009 Honda Accord w/ NAVi sound system. I got an FM transmitted iPod adapter that hooks into a wire for better sound quality, a 1100W amp, two 6.5" component speakers in the front, two 6x9 speakers in the back, a 12" PB Subwoofer, and had 3 SNIs installed to transmit the signal from the stock head unit to RCAs to go to the amp. The SNIs are located under the dashboard on the passenger side. When I got my car back, I noticed a buzzing sound coming from the back two speakers that sounded like if you left a guitar amp only partially plugged in and humming noise that came in waves of two in the form of a quick crescendo. The humming happens when I idle at any speed and when I am decelerating and come to a stop. I brought my car to the audio shop that did the system and they moved the SNIs away from the fuse box underneath the dashboard and most of the buzzing stopped but the humming continued and was even a little worse? Could it be a bad connection job in the door speaker(s)? Or the FM transmitted iPod adapter? Or just a shoddy job at connecting the whole car? Any help is greatly appreciated.

 

May be due to the Active Noise Cancellation (ANC) in your car, refer to this "sticky" thread: https://www.hondaaccordforum.com/for...ing-sub-40076/

 

red bull hit it on the head. it is the ANC.

 

I unplugged the ANCs and the car still was humming. But now, it seems as if its random. Sometimes it will hum for 2 seconds and sometimes it will go for 5. Sometimes it will happen in sets of 2 or sometimes it will just do it once and then stop. I have no idea what it is and the guys at my car audio shop could not figure it out either. They are installing a different iPod adapter that won't use an FM transmitter that plugs straight into the head unit and directly into the iPod. Will that help?

 

the issue with using multiple LOC's is introducing ground loops.

i agree the ANC will cause feedback. properly bypassing it is key.

i would try running a ground wire from the head unit chassis to the amplifier ground location. with a LOC you don't have a signal ground running to the rear.