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KEF sub fault

Discussion in 'Subwoofers' started by Jeff D, Oct 7, 2004.

  1. Jeff D

    Jeff D
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    My Kef sub which is part of my 2005.2 system has developed a fault and I wondered if anyone has had a similar problem.

    I've just sent it off to my retailer as the one year warranty period is almost over (although someone in this forum thought Kef gave five years!)

    Just in case he says there's nothing wrong with it, here's what the fault sounds like. I noticed when watching LOTR the other day (for the second time) that I could here a higher pitched 'tapping' sound coming from the direction of the sub to accompany the low bass rumble on the soundtrack (you know when they cut to Mordor). I checked when the lights went up at the end of the film and noticed that the mains lead had got tucked under the cabinet and assumed the edge of the speaker cone had been tapping against the lead. Problem solved I thought! :clap:

    Next time i listened to that same soundtrack and other similar loud low sounds, with the sub turned on its side so I could hear it directly, it was still there :confused: This tapping or crackle sound is in time with each beat of the bass sound. The cone is perfect and moves freely so I think it's probably an electronic problem.

    Anyone had the same problem?
     
  2. Nimby

    Nimby
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    Sounds like classic bottoming out.

    Your cone is exceeding its excursion limit and hitting the endstops.

    You'll have to turn it down a bit to avoid it happening again.

    It will eventually wreck the cone or voice coil. Whichever is hitting what.

    Have you calibrated your sub against your speakers with an SPL meter?

    Having the sub too loud is always the likeliest cause of bottoming.

    Nimby
     
  3. Jeff D

    Jeff D
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    Thanks Nimby.
    You might be right. I've not calibrated the sub with an SPL meter, not sure how to do this. The only thing I can say is that I set the output level by ear when I first installed the system almost a year ago and it sounded very balanced to my ears without over-the-top base. The control has always been set in the middle between maximum and minimum (fed correctly from the normal sub pre-amp output on the Denon 3803 amp). The control has never been touched and has not moved since. I've also kept it on the 'music' setting rather than 'cinema' as I preferred this setting for watching films on DVD.
    If the speaker was bottoming out, would this not have been apparent right from the start?
     
  4. Cmoth

    Cmoth
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    Based on what you have just said I would be surprised if the sub is bottoming out - maybe there is a fault with the drive unit? - What you can do is disconnect the wires from your main speakers which should mean that the sub is till working which will enable you to ascertain what the problem is more easier - i hope!
    Worse case scenario sounds like the speaker may have blown or just not operating as it should - either way Kef should be able to rectify with no expense to yourself.
     

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