Rythmic thumping coming from sub


I've had a rhythmic thumping coming from my sub (PSW125) for about a month now. It happens even when my receiver is off. I'm looking for advice on how to troubleshoot or isolate the issue so I can be certain it is the sub. Thanks for any insight.

Receiver: Yamaha RX-V479
Speakers: Polk Audio Blackstone TL250 5-piece home theater speaker system
Sub: Polk Audio PSW125 (BK) 12" 150-watt Powered Subwoofer


  • Rhythmic thumping with receiver ON = Good.
    Rhythmic thumping with receiver OFF = Not Good.

    So far, so good. :)

    Disconnect wires from the back of the sub. What do you have now (with the sub still turned on) ?
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  • It could be a wifi signal that is being picked up from something in your system or around it. Sometimes wifi streamers like Chromecast can do this. I would make certain that the pulsing is happening and start unplugging or turning off equipment until it goes away. There is a chance that it could be something within the amplifier within the sub that has gone bad, but you want to eliminate all outside possible sources first.
    HT Optoma HD25 LV on 80" DIY Screen, Anthem MRX 300 Receiver, Pioneer Elite BDP 51FD Polk CS350LS, Polk SDA1C, Polk FX300, Polk RT55, Dual EBS Adire Shiva 320watt tuned to 17hz, ICs-DIY Twisted Prs, Speaker-Raymond Cable

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  • JstasJstas Posts: 14,210
    Likely a bad ground somewhere.

    Like mrbigbluelight said, start unplugging signal wires and see if the thumping stops. If not, it's either wireless signal interference or there is a bad ground.
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  • DaveHoDaveHo Posts: 2,657
    Could be something else, but this is the classic symptom of a bad sub amplifier. @KennethSwauger
  • @pbgrasso81 it sounds like the amplifier of the subwoofer needs to be replaced. With the PSW125 it will not be a wifi signal interfering with it. It is not a bad ground either.

    If the Subwoofer is out of the sub and the subwoofer is on and it still thumps then it is definitely the amplifier in the subwoofer.

    The amplifier has a 3 year warranty on it.

    You can message me directly and I will take care of that for you.
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