Intermittent Sub Hummmmmmmmmmmmmmmmm

[wiltim2024]

Ok...Im sure this question has been asked a million times....

Im installing a JBL BassPro in my 2021 Travers because my wife seems to think she needs it. So the adventure starts.

Side note...one thing I found weird was that when checking voltage signal on speaker wires I was showing voltage on both positive and negative wires WITH the wires disconnected from the door speakers. I was expecting to have the positive show voltage and the negative show nothing...anyway.

So I originally had the Sub wired to the battery for the power and ground. I started by using the high-level inputs from the rear door speakers. The head unit doe not have RCA pre-outs. I was getting an occasional hum. It would come and go when accelerating. It does NOT do this when the car is running and just sitting. So first step is to relocate the ground. I moved to ground to the body and is about 3 feet from the sub. Still does the same thing.

Next, I read that it could be an issue with the high-level inputs (and with the detection of voltage on both + and - of speaker wires which I found weird) so installed a line converter to convert the signals to RCA. I used a Crux SOOCR-26 Wiring Interface. Still getting the same sound.

Im pretty sure the sub is good. I moved it from my Jeep which it was working fine there. Only difference is that HU has pre-outs. But I don;t think its speaker noise because even if the radio is off the noise still happens.

Any advice would be appreciated...preferably troubleshooting before throwing more $$ at parts!

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[Buck 5,000+ posts]

If you get a hum while accelerating, that sounds more like a vibrational related hum, like something isn't making connection with a conductive surface, so vibrations like wire damage or conductive surfaces somewhat tapping together or barely making contact can cause a hum like problem due to vibration, and it can be somewhat random and intermittent.

Does the sub hum when the volume is turned all the way down but the entire system is on? That would let you get some clues if the hum is coming in from the signal or power supply side of the amp, and that can help you track down if it's coming from RCA's or power wires.

As always, it's a process of elimination, unless it's just some crazy funky issue. Random electrical noise can be hard to pin down, but I would initially think it has to do with the signal side and tapping off the rear speakers. You've just gotta track down if there's signals coming in from the signal or power supply side of the amp.

 

[Buck 5,000+ posts]

Have you checked if the RCA themselves plugged into the amp are showing voltage now with the radio off or volume all the way down? Check and make sure your ring terminals on power wires and screws for terminals are all tight and no wires are wiggling.

You can buy an RCA to headphone plug wire, and use your phone as a signal source (use the phone directly as your radio preouts instead of the vehicle radio) and see if the problem happens while playing music directly from your phone to the amp, just be careful turning it up too loud. If you can't replicate the problem, the problem is on the signal side somewhere.