A subwoofer for home theater delivers deep, room-rattling bass to enhance concerts, boost the impact of action films and add a dramatic dimension in sound to the theater experience. These low-frequency speaker systems are typically powered by an internal amplifier with a cable connection to the main home theater receiver. If something goes wrong with your subwoofer, check the power and cables first; then move on to other possible trouble sources.
Check the power
Most subwoofers for home theater use are self-powered. This means the sub has a built-in amplifier to deliver the power that drives the speaker coil inside. Check to make sure the subwoofer's power cable is plugged firmly into an electrical outlet, preferably a power strip with a circuit breaker. Check the power strip as well to make sure it has not tripped from an electrical surge. Reset the power strip if necessary. You can also try plugging the sub into its own dedicated power strip or outlet, away from other components that could be causing interference.
Most subs have a power-indicated LED light that will turn on when the sub is powered up. The light can be found on the front or back of the cabinet. On some models, the light will turn off if the subwoofer is not in use for five minutes or more, and the sub will switch to dormant mode. Turning off the power and turning it back on may immediately reactivate your sub.
Subwoofers are connected to a separate amplifier or receiver by means of speaker wire or a dedicated cable with RCA-type plugs on either end. Check the connections behind the sub and your receiver or amp to be sure the cable is securely plugged in. If this doesn't solve the problem, try switching out for a different audio cable to see if your problem is the cable itself. Alternatively, you could isolate the problem by connecting a different speaker to the cable and see if it works. If the second speaker doesn't work, you either have a bad audio cable or a problem with the subwoofer output jack on your amplifier or receiver.
Odd noises, gain settings
With all cables and power cords securely plugged in, adjust the volume on your amplifier to about midway, cue up a movie or TV program and adjust the gain control knob on the back of the sub. You should know that the audio on some DVDs and Blu-Ray discs may not be mixed to produce a lot of low-frequency bass, so you may not get a lot of action from your sub. Choose a movie with a lot of car chases, explosions, airplanes and action to test the sub. If the gain setting is dialed to the maximum and you still get no sound, check the circuit breaker on the back of most subwoofers and press the button to reset. If the sub is equipped with replaceable tube fuses, replace the fuse and check the component.
If your sub is producing odd noises, especially a buzzing sound, that's a sign that the speaker coil may be blown or is going bad.
Hope for the best by moving the sub to a different spot in your home theater. Subs that are too close to the television or other high-powered devices with electromagnets inside can produce signal interference and odd noises.
If you can remove the grille on the front of your sub, check the speaker cone for damage. Small rips or holes may be fixed with a special sealant available at electronics stores. The sealant is applied with a small brush on the inside of the product lid. Use small strokes to brush on the sealant around the rip to seal and hopefully repair your sub.
If you still hear a persistent buzzing sound, replacing the entire sub is the best option, since the cost of repairs may be greater than buying a new subwoofer.
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