I have a new Polk PSW505. My receiver is an Onkyo tx-nr656.

There is a very annoying pulse sound from the subwoofer, almost like a rapid heartbeat. I thought it was the sub, so I exchanged it for a new one. Still, same exact problem. I bought two different high quality sub cables, both did the same thing. The LPF of LFE is set at 120Hz. As most suggest, the lowpass knob on the sub is turned all the way to 120Hz.

I have tried both sub outs on the receiver, two different cables, and two brand new PSW505 subs. I have adjusted/tried every input, every setting, and only one thing helps.

If I turn the lowpass knob down to around 80, maybe 90 it goes away. But then the bass isn't really adequate. Any ideas? If the sub is on, making the noise and I unplug the cable, it stops. So is it my receiver (also new), but then why does turning down the low pass on the sub help? I have had two other subs, a Klipsch and a smaller Polk hooked up previously and never had this issue with the same reciver which leads me to think it is the sub.


  • KennethSwaugerKennethSwauger Moderator Posts: 6,128
    Do you happen to have a wireless alarm system in your house?
    Regards, Ken
    "Passion is inversely proportional to the amount of real information available", G. Benfield
  • No, and the wifi router is 2 stories above. Can it be electrical? Like, the power strip it's plugged into? I just don't have another location to plug it in but thought it might be some kind of ground loop interference.
  • KennethSwaugerKennethSwauger Moderator Posts: 6,128
    The reason I asked about the wireless alarm is that I believe something external is causing the problem rather than the subwoofer itself. As a test try removing the sub cable from the receiver and connecting it to either the right or left audio output of your DVD player (assuming you have one). Then play a CD and slowly turn up the sub's volume, there should be plenty of bass and no pulsating.
    "Passion is inversely proportional to the amount of real information available", G. Benfield
  • Ok, I will try that shortly. But why is it audible once the lowpass is turned up past 90? How does external interference relate to that? Just curious.
  • Pretty sure I fixed it! I tried turning off the receivers wi-fi, no luck. Tried hooking it up straight to a dvd player, no pulse noise. So, looking for a source of interference I remembered I had a Chromecast plugged into the back if the receiver. Took that out, noise seems to be gone! :)
  • KennethSwaugerKennethSwauger Moderator Posts: 6,128
    Good, I'm glad you were able to figure out the problem.
    "Passion is inversely proportional to the amount of real information available", G. Benfield
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