Subwoofer Hum

This is likely a ground loop causing current to flow through your subwoofer audio cable because of voltage differences between the subwoofer electrical ground and your equipment ground.

  1. Disconnect the cable to the subwoofer to see if the hum disappears.  If you remove the cable and the hum goes away you have a ground loop problem.  If the hum persists without the audio cable your subwoofer may be defective or the subwoofer volume may be too high.
  2. If you have a ground loop locate the source by disconnecting equipment with grounds connected to your receiver with either a video or audio cable until the hum goes away.  This excludes optical audio connections.  Common causes are cable TV or satellite TV connections to the cable box or TV, different ground potentials caused by equipment plugged into different outlets, different electrical phase on devices and poor equipment design.
  3. If that does not locate the source try replacing the cable running to the subwoofer.  Sometimes a defective cable can cause this.
  4. If the source is the cable TV either correct the grounding error or use a Jenson isolator.  You can also consider using an optical audio connection from the cable box to stop this, but if you are switching video through the receiver this is not likely to work.
  5. If the source is the satellite TV you must fix the grounding problem on your satellite system or use an optical audio connection and remove video switching from the receiver.
  6. If the source is differences in electrical grounds you must either have an electrician fix the electrical ground problem in your home or use products like these.
  7. If the source is the receiver or subwoofer itself it may be necessary to send it back for repair or replace it.  Only resort to this after exhausting all other options.

More information on this topic can be found in this great article by Bill Whitlock.

6 Comments
Cheap Electronics

Super-Duper blog! I am loving it!! Will be back later to read some more. I am taking your feeds also

Cheap Electronics

very nice posting… i have a set home theater at home and i use subwoofer however

Allan McQueen

Awsome site! I am loving it!! Will be back later to read some more. I am taking your feeds also.

silvio inagaki

Just want to thank you for the information. It really helped a lot!
I´ve just solved 99% of my subwoofer hum and wanted to leave my comments.
Problem appeared when I connected a Denon ST501 receiver with my active sub-woofer (DIY project with 12V/30A switching PS + 250W Class D amplifier).
– at first I realized the house grounding was not “grounding” properly my power supply so I made an additional one at the garden (3 x 1/2″ cooper sticks/ 6 feet each).
– after this I also checked the Denon chassis had a voltage of 40-50Vac when measured to the new ground of my PS. Problem is that Denon has only 2 prong!!
– So I just got one of the chassis screws and connected it to the ground screw of my PS.
ps: even knowing that many comments tells you to do not ground the Denon chassis. That was the most effective measure to reduce the hum.
Another tip: if you want to be sure you have a ground loop, replace your audio source by your cell phone audio. Since it is not connected to your house AC net you should stop the hum.

South

Very informative, thank you, although i’ve never personally had this issue, ill bookmark it just in case.

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