I installed a JBL subwoofer in my car two months ago and since then there's been this annoying humming sound, especially when the engine's running. The cable is routed properly and the sub is wired up correctly. Could it be a power supply issue or do I need to adjust the frequency?
The humming almost always comes from poor grounding or ground loops - check if your subwoofer's power cable and the RCA cables from the amp are routed separately in space (they definitely shouldn't run right next to each other). If that's already the case, try using a separate ground cable running directly from the battery to the chassis at the sub, that fixes the problem in 90% of cases. 😊
With car subwoofer hum, a lot of people immediately think of grounding issues, but it's often overlooked that a poor ground connection from the amplifier itself can also cause the problem - check if the ground wire from the amp is really properly seated on bare metal of the body and isn't just screwed on superficially.
The other answers are pointing in the right direction, but the real problem usually sits somewhere else: Check the subwoofer's power cable itself - if it's run right next to or bundled together with the RCA cables, that creates a classic ground loop. The RCAs need to be spatially completely separated from the power cable, ideally on the other side of the car. Plus, it's worth checking the amplifier's ground connection to the chassis ground point - a lot of people underestimate how important a large, clean metal surface there is. If the hum is still there after that, it could also be a cheap or too-long ground wire causing the problem - a short, thick cable run directly to the battery negative terminal often works wonders.
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