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.


  • VR3VR3 Posts: 24,292
    Grab you a ground defeat for the power cable ie, going three prong to two prong, see if that solves your problem
    - Not Tom

    "No, that's silly talk. Dude, you can't possibly be this audio dumb so quit the act." - Doro
  • I did that, no help. Plus it's already just a 2 prong. I tried plugging it in to a different outlet across the room with an industrial gauge cord just to get it away from the other circuit but no change.

    Again, it seems related to the lowpass being turned up past 90.
  • msgmsg Posts: 6,383
    Do you have bass management enabled on your AVR, in other words, is your AVR controlling the LFE?

    If so, can you turn it off, or set to bypass or full range so that you get full range to the sub and use the sub's crossover? Just as a test.

    Be good to test it with a different receiver to rule that out, but not like everyone happens to have a spare one laying around.
    I disabled signatures.
  • 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! :)
  • Dennis GardnerDennis Gardner Posts: 4,901
    Glad you found it! Sometimes all the signals in the air cause issues that are hard to find.
    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

    2 Channel Thorens TD 318 Grado ZF1, SACD/CD Marantz 8260, Soundstream/Krell DAC1, Audio Mirror PP1, Odyssey Stratos, ADS L-1290, ICs-DIY Twisted , Speaker-Raymond Cable
  • preeth64preeth64 Posts: 1
    Replace the 47uF -63V capacitor there are two of them, the problem will be solved. Works like a charm
  • waksalanowaksalano Posts: 1
    I'm having this exact same issue but I don't have a Chromecast or anything extra plugged into my receiver. Any help?
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