How to fix a thumping sound problem in a jbl subwoofer 135

Updated February 21, 2017

The JBL Sub 135 is a powered subwoofer for home theatre. The unit produces low-frequency bass signals when connected to an audio-video receiver with a playback source, such as a DVD or Blu-ray player encoded with multichannel audio. If your JBL Sub 135 produces a thumping sound, try adjusting the control settings and making other adjustments before disconnecting the component and taking it to a shop for repairs.

Pull the JBL Sub 135 away from the wall, which can absorb and reflect vibrations from the sub.

Dial the gain and volume controls on the back of the subwoofer counterclockwise while playing an audio source until the thumping stops. The gain (power) control may be set too high for the sub to handle the signal from the AV receiver.

Lower the volume setting on the AV receiver to reduce the signal output to the JBL sub.


Adjust the JBL's crossover control on the back panel counter-clockwise to direct less of the AV receiver's signal output to the subwoofer. Higher frequencies will be sent to other speakers connected to the system, reducing the overall load on the JBL.

Things You'll Need

  • AV receiver connected to the JBL Sub 135
Cite this Article A tool to create a citation to reference this article Cite this Article

About the Author

James Clark began his career in 1985. He has written about electronics, appliance repair and outdoor topics for a variety of publications and websites. He has more than four years of experience in appliance and electrical repairs. Clark holds a bachelor's degree in political science.