Diagnose and Eliminate Subwoofer Hum and/or Buzz

So you've just cabled up a new speaker to your system, placed the subwoofer for best performance, and even tweaked the audio equalizer so that everything sounds perfect to your ears. You sit down to relax and listen, but notice that something is off. There is a very conspicuous, persistent hum stemming from the subwoofer and it shows no signs of going away. So how and what just happened?

Subwoofer hum or buzz is a low-level noise that can be present whenever a passive or powered subwoofer is turned on, regardless if it is playing or not.

This 60 Hz (also known as 60-cycle) hum is a direct result of being plugged into an AC wall outlet. Sometimes it's very obvious. Sometimes it takes some focused listening to notice. Either way, there are a few methods to try in order to correct the situation without having to resort to filtering out the noise, which also ends up stripping out audio signals (i.e. "throwing the baby out with the bathwater"). Usually, all it takes is changing the way the subwoofer connects to power.

Difficulty: Easy

Time Required: 15 minutes

Here's How:

1. Change the polarity of the subwoofer's connection. This is probably the simplest fix to try, since all it involves is reversing the power plug's orientation. Sometimes, one of the prongs can be wider than the other, thereby preventing the reversal. In such situations, an AC ground adapter can be used to effectively reverse the polarity. Most of these adapters have uniform-sized prongs and are readily available at most any local home improvement store.

1. Reverse other plugs. When components are sharing the same source, such as a power strip and/or surge protector, the culprit may not be the subwoofer at all. It could be some other 2-prong AC plug. So, one by one, reverse the orientation of the other plugs to see if it makes a difference. Be sure to power everything off first before each attempt.

1. Separate the cables. If you have power and/or audio cables clustered together in bundles, signals can bleed over and create noise due to proximity. Try to space cables apart so the fields created by moving current won't interfere with each other. If it's not possible to set sufficient distance, consider upgrading the audio cables to ones with more effective shielding.
2. Switch outlets. Sometimes the subwoofer hum is caused by a ground loop, which can happen when it's fighting a second device for possession of the ground. If you have another 3-prong piece of equipment sharing the same wall outlet (or power strip and/or surge protector) as the subwoofer, you'll want to move the subwoofer to another AC circuit in the room. It may be necessary to use an extension cord in order to reach a wall outlet that is separate from the rest of the stereo system.
3. Use an audio isolation transformer. If the previous grounding techniques haven't worked, then you may need to purchase and install an audio isolation transformer. Many are designed for powered subwoofers and connect in-line with the cables. When successful, they instantly resolve ground loops.

What You Might Need:

• AC Ground Adapter
• Extension Cord

• Audio isolation transformer