If a subwoofer is not outputting any audio, no longer powering on, or is powering off within a few minutes, the first thing to check is the subwoofer's built-in amplifier.
Please Note: This is geared towards "home theater" subwoofers, not the subwoofers that come with our soundbars or computer speakers.
To do this, let's try something called a "buzz test":
- Make sure the sub is plugged in, powered on and has a sub cable plugged into the LFE port on the back of the subwoofer
- On the back of the sub, turn the gain knob up to at least 50-60% (about 12 or 1 o'clock on the dial)
- Do not plug the other end of that sub cable into your receiver or sub output
- Instead, grab the unplugged end of the cable and touch the male RCA post a few times to see if you can hear the sub give you a "buzz" sound each time you touch the post
HERE IS A PICTURED EXAMPLE OF A SUB CABLE WITH THE RCA POSTS HIGHLIGHTED
If you do not hear any buzz each time you touch the RCA post, then the built-in amplifier has likely gone out and will need replaced/repaired.
For steps on troubleshooting the cone woofer portion of the subwoofer, please see the article - Troubleshooting the Cone Woofer of a Subwoofer