Subwoofer Hum

jcircus
jcircus Posts: 3
edited November 2012 in Troubleshooting
Hello,

I recently purchased the RM6750 home theater speaker kit. The sound is awsome, however the subwoofer has a constant hum even when everything (exept power) is disconnected. I have tried different outlets around the house, and purchased a good APC power strip. I dont think this is normal, but I could be wrong. any help is appriciated.
Post edited by jcircus on

Comments

  • jhw59
    jhw59 Posts: 348
    edited July 2012
    is your sub cable grounded/shielded? if not, I've been pleased with the inexpensive one I purchased from blue jeans cable. No more hum once I installed it.
  • jcircus
    jcircus Posts: 3
    edited July 2012
    jhw59 wrote: »
    is your sub cable grounded/shielded? if not, I've been pleased with the inexpensive one I purchased from blue jeans cable. No more hum once I installed it.


    Yes, I am using a Belkin Pure AV subwofer (double shielded) cable. but that doesnt matter. Even with the audio cable disconcted from the sub, the hum is still there.
  • jhw59
    jhw59 Posts: 348
    edited July 2012
    hmmm...I wonder if there is a loose connection in the sub somewhere?
  • ken brydson
    ken brydson Posts: 8,640
    edited July 2012
    Might be a ground loop hum. Try a cheater plug and see if it goes away...
  • jcircus
    jcircus Posts: 3
    edited July 2012
    Might be a ground loop hum. Try a cheater plug and see if it goes away...

    Sorry to be ignorant, but what is a cheater plug?
    Also, I went throught the tests on this site regarding "ground loop hum" - http://oreilly.com/pub/h/4241 to remove the subwoofer hum. Like I said before... removing the RCA cable between the subwoofer and receiver does not get rid of the hum. just being plugged into any power outlet in the house, creates the hum.
    Does Polk support folks reply to this forum, or do i need to contact them directly?

    Thanks for your suggestions.
  • EndersShadow
    EndersShadow Posts: 17,517
    edited July 2012
    A cheater plug is an adaptor that is 3 prongs on one end 2 on the other, or vice versa. Use whichever one you need (I forget if polks subs are 2 or 3 prong plugs)
    "....not everything that can be counted counts, and not everything that counts can be counted." William Bruce Cameron, Informal Sociology: A Casual Introduction to Sociological Thinking (1963)
  • shumi02
    shumi02 Posts: 10
    edited July 2012
    is your sub cable grounded/shielded?
  • mrme73
    mrme73 Posts: 1
    edited July 2012
    I have the same issue, I recently purchased a RM705 speaker system and it has a continuous hum. With the power switch off and the inputs disconnected the unit still makes a buzzing sound continuously. This is not related to the ground feedback issue as it is only a 2 prong plug and there are no inputs connected. I don't even have a receiver to connect it to yet.
  • Kschantz
    Kschantz Posts: 1
    edited November 2012
    I've had the RM6750 for a little over a year then all of the sudden the other night it started making a constant humming noise. I disconnected the audio cable and it still does it. I also moved the plug to a different outlet on another breaker - no change. What should I do? please help.
  • jhw59
    jhw59 Posts: 348
    I hate to say it but my hum has returned. I used a cheater and plugged it into the wall. The sub cable has grounds and is shielded(audioquest). The hum seems to vary in loudness as I move closer and away from the sub-Carver true signature. Anything I'm overlooking?
  • tonyb
    tonyb Posts: 32,902
    Try the cheater plug on the receiver.
    HT SYSTEM-
    Sony 850c 4k
    Pioneer elite vhx 21
    Sony 4k BRP
    SVS SB-2000
    Polk Sig. 20's
    Polk FX500 surrounds

    Cables-
    Acoustic zen Satori speaker cables
    Acoustic zen Matrix 2 IC's
    Wireworld eclipse 7 ic's
    Audio metallurgy ga-o digital cable

    Kitchen

    Sonos zp90
    Grant Fidelity tube dac
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  • jhw59
    jhw59 Posts: 348
    tonyb wrote: »
    Try the cheater plug on the receiver.

    thanks! That seems to have solved the hum issue.
  • tonyb
    tonyb Posts: 32,902
    jhw59 wrote: »
    tonyb wrote: »
    Try the cheater plug on the receiver.

    thanks! That seems to have solved the hum issue.

    Your welcome. Usually these small ground loop problems occur when adding things to your system. Cables are also a grounding device and the more you have connected to the main source....receiver or pre amp, the more likely an annoying ground loop will occur from having too many grounds at one point.

    Of course that's not always the case, and ground loops can be caused by a variety of things, but it's one of the first to check and the easiest.

    HT SYSTEM-
    Sony 850c 4k
    Pioneer elite vhx 21
    Sony 4k BRP
    SVS SB-2000
    Polk Sig. 20's
    Polk FX500 surrounds

    Cables-
    Acoustic zen Satori speaker cables
    Acoustic zen Matrix 2 IC's
    Wireworld eclipse 7 ic's
    Audio metallurgy ga-o digital cable

    Kitchen

    Sonos zp90
    Grant Fidelity tube dac
    B&k 1420
    lsi 9's
  • dpowell
    dpowell Posts: 3,050
    Do you have cable TV? If so, this can cause the hum issues. You can buy a ground loop isolator that connects inline with your coax cable to resolve the issue. Of course if you're OK with the cheater plug on your receiver, that works as well but removes a layer of protection that the receiver was designed to have.
    ____________________________________________________________ polkaudio Fully Modded SDA SRS 1.2TLs + Dreadnaught, LSiM706c, 4 X Polk Surrounds + 4 X ATMOS SVS PB13 Ultra x 2Pass Labs X1, Marantz 7704, Sunfire Signature Cinema Grande 400, ADCOM 7807, Panasonic UB420, Sony SCD-C333ES, EPSON Pro Cinema 6050
  • tonyb
    tonyb Posts: 32,902
    edited January 2015
    dpowell wrote: »
    Of course if you're OK with the cheater plug on your receiver, that works as well but removes a layer of protection that the receiver was designed to have.

    True in theory, if your going directly into a wall outlet. If your going into a Power conditioner though, you still have a layer of protection against surges and spikes. Of course if you had a good power conditioner, you may not need the cheater plug either.

    Back in the day, we used to run a simple wire from a case screw to another piece to get rid of some hum issues. I used to use a cheater plug for over 5 years, with no ill effects. Yes, it's a temporary fix, but it will give you some time to save coin for a decent power conditioner. Better cabling and Hospital grade wall outlets will help also.



    Post edited by tonyb on
    HT SYSTEM-
    Sony 850c 4k
    Pioneer elite vhx 21
    Sony 4k BRP
    SVS SB-2000
    Polk Sig. 20's
    Polk FX500 surrounds

    Cables-
    Acoustic zen Satori speaker cables
    Acoustic zen Matrix 2 IC's
    Wireworld eclipse 7 ic's
    Audio metallurgy ga-o digital cable

    Kitchen

    Sonos zp90
    Grant Fidelity tube dac
    B&k 1420
    lsi 9's
  • dpowell
    dpowell Posts: 3,050
    Seems like I see Monster HTS 3500's on CL all the time for under $100. Cheap insurance.
    ____________________________________________________________ polkaudio Fully Modded SDA SRS 1.2TLs + Dreadnaught, LSiM706c, 4 X Polk Surrounds + 4 X ATMOS SVS PB13 Ultra x 2Pass Labs X1, Marantz 7704, Sunfire Signature Cinema Grande 400, ADCOM 7807, Panasonic UB420, Sony SCD-C333ES, EPSON Pro Cinema 6050
  • jhw59
    jhw59 Posts: 348
    Thanks for all the comments. I have an Acme hospital grade outlet and just installed a APC LE1200 Line-R 1200VA Automatic Voltage Regulator. I noticed a little hum but when I moved the Fios cable it disappeared. I may need to install a ground loop isolator. Any advice on where to purchase it?