You’ve connected a new speaker to your system, positioned the subwoofer for best performance, and even adjusted the audio equalizer so everything sounds perfect to your ears. You sit back to relax and listen, but realize something is wrong. The subwoofer emits a persistent and striking hum that shows no signs of going away.
Subwoofer hum or hum is a low-level noise that can be present any time a powered or passive subwoofer is turned on, whether it is playing or not. This 60 hertz hum is a direct result of being plugged into an AC outlet.
Sometimes the buzzing is obvious. Sometimes it takes a little concentration to figure it out. Either way, you can correct the situation without resorting to noise filtering, which also ends up removing audio signals. Usually all that is needed is a change in the way the subwoofer connects to power.
Ways to Eliminate Subwoofer Hum
You can take several approaches to get rid of the annoying ringing. If the first suggestion doesn’t work, try one of the others.
- Change the polarity of the subwoofer connection. This is probably the easiest solution to try because all it involves is reversing the orientation of the power plug. Sometimes one of the tips is wider than the other, which prevents inversion. In such situations, use an AC ground adapter to reverse the polarity. Most of these adapters have uniform sized tips and are readily available at local home improvement stores.
- Reverse other plugs. When components share the same source, such as a power strip or surge protector, the subwoofer may not be the culprit at all. It could be another two pin AC plug. One by one, reverse the orientation of the other plugs to see if it makes a difference. Be sure to turn everything off before each attempt.
- Separate the wires. If you have power or audio cables bundled together, signals can bleed through and create noise due to proximity. Try to separate the wires so that the fields created by the moving current do not interfere with each other. If it is not possible to separate them far enough, change the audio cables to ones with more effective shielding.
- Change outlets. Sometimes the subwoofer’s hum is caused by a ground loop, which occurs when the subwoofer is fighting a second device for ground possession. If you have other three-prong equipment that shares the same outlet, power strip, or surge protector as the subwoofer, move the subwoofer to another AC circuit in the room. It may be necessary to use an extension cord to reach a wall outlet that is separate from the rest of the stereo.
- Use an audio isolation transformer. If the above grounding techniques have not worked, you may need to purchase and install an audio isolation transformer. Many are designed for powered subwoofers and connect in-line with cables. They instantly resolve ground loops.