Thoughts on how to diagnose speaker-related noise?

[grs]

I have a 2010 Legacy with the Harmon Kardon radio package. Seemingly at random, I have popping/interference noise from either my right (or my left, to a much lesser degree) front speaker -- but not generally at the same time.

 

The dealer replaced the radio as a shot in the dark, but the speakers still randomly pop. Since it is seemingly random (i.e., I don't yet know how to reproduce it at will) and it has never happened at the dealership, the dealer says I'm now on my own.

 

I'm pretty handy with a screwdriver and wrench but am a total newbie at diagnosing something like this, esp. as it's something I didn't install.

I looked through the threads and didn't see anything that looked exactly on point. I would really appreciate any recommendations on how to isolate this to be able to diagnose it.

 

Additional details are as follows:

 

The popping/interference from the right speaker is generally much louder and more frequent (and is loud enough that I cannot tell if the left speaker is doing it, too). When it occurs, it doesn't last long -- no more than a few seconds to a few minutes at a time. I cannot turn it down with my volume control, and it continues with the radio turned off. (The radio is almost always on in my car, so the noise always starts when the radio is on.) Also, it does not change pitch when I'm driving/accelerating but is a constant volume. I have not, to my recollection, ever heard it when I am connected to my phone via bluetooth.

 

The closest description of it that I can think of is the type of interference that some smart phones (like blackberries) will cause on an office speakerphone (like static-y morse code), but this popping noise will happen with or without other technology present. I'm still inclined to think it's some sort of interference because where it happens most is in rural areas as I drive under some normal telephone/electric lines (i.e., they are not high voltage), but it does not happen every time I drive under those lines ... just with the most frequency there. (E.g., on my normal commute with the car, it might happen once every 2 weeks; when I'm in this rural area, it happens once or twice a day, including on the highway, under those power lines, crossing bridges, etc.)

 

Thanks in advance,

Greg

[garbo41610]

As a starting point for the troubleshooting. I would check the terminations at both the speaker end and the amplifier end. There may be a stray strand of copper shorting out. This will however obviously require taking the door trim off. Which isn't too difficult, I thought I would just mention that taking a door trim off should NEVER be done with a screwdriver.

 

Next I would check that the earth to the amp is in good condition, I'm not sure how the earth for the amp is terminated, whether it be close to the amplifier itself or up in behind the head unit (it's not something I have had to check as yet).

 

Next, I would check that all the terminations at the head unit end are all ok and there is nothing shorting out behind it.

 

Hope this helps.