How to Eliminate a Humming Sound on a Home Theater Subwoofer


An irritating humming sound from a home theater subwoofer is typically caused by one of two problems: It's either coaxial cable interference from the cable TV or satellite service provider; or a grounding problem between the sub and the audio-video receiver that drives the home theater system. Fixing a coaxial cable problem requires a low-cost surge protector that has coax cable jacks as well as the electrical outlets. A grounding issue with the receiver and sub requires some simple rearrangements of power cables.

Things You'll Need

  • Surge protector with in/out RF cable connectors
  • Coaxial cable with connectors on both ends
  • Disconnect the coaxial cable at the back of the satellite receiver or cable box by unscrewing the coupler on the cable end.

  • Attach the cable to the RF IN jack on a surge protector and tighten the coupler clockwise.

  • Connect a second coaxial cable from the RF OUT jack on the surge protector to the input on the cable box or satellite receiver. If this stops the hum, congratulations: You're done.

  • Unplug the subwoofer's electrical cord from the power strip or wall outlet if it is connected to the same circuit as the AV receiver. The amp in the AV receiver and the amp in the subwoofer are in conflict over the grounding of the electrical circuit.

  • Plug the subwoofer into its own surge protector and connect the surge protector to a different wall outlet than the AV receiver uses.

  • Disconnect the subwoofer cable from the back of the sub and the AV receiver if all other measures fail to stop the humming. Reverse the plug connections so the plug that had been connected to the receiver is now connected to the subwoofer. Turning the cable around may solve a problem known as ground-loop hum by reversing the shielding wire inside the cable.

Tips & Warnings

  • Some subwoofer cables are embossed with arrows indicating the signal direction. Plug the cable so the arrow pointing out on a plug is the end connected to the subwoofer. The plug with the arrow on one end pointing down the length of the cable should be connected to the receiver.
  • Turn off the amplifier and subwoofer whenever connecting or disconnecting any cables. This prevents a power surge that could damage the electronics.

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