Weird noise from subwoofer during Test-Tone

Discussion in 'Archived Threads 2001-2004' started by Willem Vos, Apr 9, 2002.

  1. Willem Vos

    Willem Vos Stunt Coordinator

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    I just noticed something while I was calibrating my sub. When the pink noise from the internal receiver test-tone (denon 3802) is outputted to my sub, it not only produces bass, but some weird resonance noise (a bit like a geiger counter...) coming from inside(!) the sub. I don't think it's the driver.

    First I thought something was shaking due to the bass, but it wasn't that. Is it some electronic noise?

    I put in a dvd after that, toned down the other channels except the sub's, and listened again, but the bass sounded fine...

    What could this be?!
     
  2. Willem Vos

    Willem Vos Stunt Coordinator

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    *bump*
     
  3. Travis G

    Travis G Stunt Coordinator

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    Willem,

    I'm thinking you probably have a case of voice coil rub. It happens when the voice coil is not centered properly in the gap. The speaker could have been defective when you purchased it. How long have you owned the subwoofer? Although the problem only becomes obvious when you play sine waves, it may get worse over time.

    Travis
     
  4. Willem Vos

    Willem Vos Stunt Coordinator

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    Thanks Travis,

    The sub is brand new (REL Q150E)

    I think by voice coil you mean the (heavy) rear end of the speaker. Wouldn't a voice coil rub cause a very loud noise? This is not the case, I only noticed it when I sat next to my sub to adjust the volume.

    Also, is there an explanation why this would only be audible during testtones?
     
  5. Willem Vos

    Willem Vos Stunt Coordinator

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    Just read on another forum that someone with the same problem exchanged his sub, but the new one had the same problem. Could this be normal?
     
  6. Willem Vos

    Willem Vos Stunt Coordinator

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    bump
     
  7. Willem Vos

    Willem Vos Stunt Coordinator

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    I'm still unsure what to do...

    I've read that the sound coming from a sub is never a hundred percent "clean", but I think I'm hearing the sound (like a geiger counter / or something vibrating inside the sub) during certain bass sequences now.

    I'm relatively technical, and I'm wondering if a voice coil rub (if that's what it is) can be easily fixed? The warranty is still valid, so I could just bring it back to the store...
     
  8. Cees Alons

    Cees Alons Moderator
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    Willem,

    Spurious sounds like that shouldn't be there.. period.

    Rel's are among the best subs in the market and if it's new, just go back to your seller and see what they can do or have to say about it.

    Of course, you must try to make sure first, if possible, that it isn't in the signal you're feeding to the sub.

    Cees
     
  9. Richard_s

    Richard_s Second Unit

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    Just a guess:

    A test tone produces a sustained signal that could couple into a resonance of something in the Subwoofer "sympathetic vibration" The gain of such vibration since it is continuously being supplied and in phase can cause tremendous "noise" from whatever is vibrating at the given frequency (it could even be a harmonic meaning a multiple of a frequency being supplied by the subwoofer so the "noise" you hear can be above 180HZ).

    Now when playing music the bass is short lived at any given frequency and more random not allowing for this "resonance" to be apparent.

    Like I said this is just a guess but make sure it is actually the subwoofer and not something near it. If its internal to the subwoofer not sure how to deal with that. Try changling the overall vibration characteristics of the case by placing a heavy weight on it as a test and see if that changes anything.

    Now I have a PB12 in a corner where I have forced hot water baseboard and I had a similar sound as you describe when running the AVIA sweep test. That cause the radiator to resonate but it sounded just like it was the subwoofer. I put duct tape on the item and that stopped the vibration.

    Side note: To protect the subwoofer from the heat of the radiator I stuffed towels underneath and plugged the registers with Pipe insulation to keek the radiator from putting too much heat into the corner where my subwoofer is.
     
  10. Steve_Ma

    Steve_Ma Second Unit

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    You might want to try something like the stryke disk. www.stryke.com. This will allow you to play various test tones at different freqs. If it's only happening at a certain freqs or if it's hapening with just sine waves vs warlbles, this sort of info might help you isolate the problem. The stryke disk is also handy to have around for calibration and room resonse reasons as well.
    Good Luck,
    --Steve
     
  11. Richard_s

    Richard_s Second Unit

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    The product that Steve_Ma recommended would help to isolate the "resonance" I referred to above if that is the problem. A note of caution. Run such tests first at a low volume and do not dwell too long on a given frequency that is resonating something. Constructive "sypathetic vibration" resonance can damage whatever It is resonating (remember the bridge that fell down - "Galloping Gertie" I think was the name).
     
  12. Willem Vos

    Willem Vos Stunt Coordinator

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    Thanks a lot guys, but the sound is definitely coming from inside the sub,

    I tried several things, because from a distance it really sounds like cutlery is shaking from the bass, but placing my ear on the sub leaves no doubt.

    I screwed out the spikes today, because at the last moment I thought that could be it, but to no avail...

    I'm taking it back.

    I'll be without a sub for a while, but what the heck, I want this thing fixed...

    $700 for a sub and still I get rubbish... just shows that more money doesn't always guarantee an error-free product.
     

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