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Crackling speaker

Discussion in 'Home Cinema Speakers' started by fyonn, Sep 28, 2005.

  1. fyonn

    fyonn
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    Hiya folks,

    for the last 2 weeks I've been trying to work out why my system sounded "odd" but I wasn't really trying to find the issue, too busy. last night I sat down with a test disc and tried to find the problem, and I've discovered that my left speaker is crackling at certain frequencies. it's like little bits of static that interfere with the signal at certain points.

    we're talking around male voice frequencies, but it's nt just that, but more widespread. I can't see any damage to anything and the speaks have been fine for about 4 years.

    I know that I'm gonna have to take it to a shop, and probably back to the manufacturer for repair, but I suppose I was hoping to get an idea of what it might be, what it might cost to fix it and what might have caused it.

    the speakers themselves are Kef Reference 1 floorstanders. I suppose that if the repair cost is going to be more than about £400 than it's probably not worth it.

    dave
     
  2. chedmaster

    chedmaster
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    i shouldnt think the repair cost will be any where near that, but i could be wrong :)
     
  3. fyonn

    fyonn
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    well, the broken driver is one of kef's top end uni-q dual concentric tweeter/mid range units so I guess it would have to be replaced as an item, rather than just replacing a broken tweeter or midrange. no idea how much one of those units would cost, followed, by how much will it cost to get someone to do the work?

    not sure, but I'll call a shop tmw and see what they say to me.

    dave
     
  4. the mechanic

    the mechanic
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    Hi,
    First thing I would do is swap over the speaker cables (Do this at the amp end for convienience) and see if the crackling is still in the left channel. If it is then the prob lies with the speaker, if the crackling comes from the right channel then its the amp at fault.
    If the fault lies with the speaker an easy way to check is to remove the grille, then with two thumbs either side of the bass cone (near the centre), press GENTLY inwards then release (repeat as neccessary) and listen/feel for any roughness or grating. If it does this indicates the voice coil has "burnt out" as they say. The cone of the speaker should move in and out under finger pressure with no noise/grating if it is OK.
    This happened to one of my Mission 773e's bass drivers (same symptoms as you are getting), and I ordered a replacement driver direct from Mission and it cost from memory £35.00 inc delivery.
    Replacing a "blown" driver is usually a simple procedure, normally needing nothing more than a screwdriver (or allen key / torx driver depending on what fittings are used to screw it down), and obviously a steady hand so you dont slip and puncture the new unit when re-fitting it.
    The cables attaching to the terminals on the speaker are normally spade type connections, and easily pull off for replacement.

    Keep us updated.
    All the best,

    Graham
     
  5. Timmy C

    Timmy C
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    Can you let us know the outcome of this? I've had similar problems with old Mission speakers but I never got to the bottom of it. I'd be interested to know if it turns out to be a speaker or amp problem.

    Good luck!
     
  6. fyonn

    fyonn
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    I already did this, and the fault is with the speaker. when I swapped left and right, it was still the left speaker that had the fault.

    I'll try the the other suggestion tonight about moving the cone and feeling for grating.

    I'll have to have a look and see how easy it is to get into the speaker, unlike the missions, my kef' don't have obvious exposed bolts keeping the driver in place, so I might have to remove the front baffle completely or something.

    if I got a replacement tweeter/midrange unit, would a new driver at one side, and an old one at the other cause problems do you think?

    dave
     
  7. the mechanic

    the mechanic
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    Dave,
    I should'nt think a new driver would cause any problems against the old one. When I changed the blown driver in my 773e there were no decernable differences between one or the other. I would suggest you run the affected speaker in for a while after replacement so it has time to take on a less pronounced "new speaker" sound.

    Keep us up to date please,

    Graham.
     
  8. fyonn

    fyonn
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    oh yeah. the faulty driver sounded almost like it was breathing as I moved the cone. did the same on the good driver and it was silent. could both feel and hear the burnt out voice coil.

    so what causes a voice coil to burn out? and for that matter, what does it mean to say that the voice coil has burnt out? what has actually happened?

    looks like I'd better write down the serial number and call kef tomorrow to ask what a new driver will cost.

    dave
     
  9. fyonn

    fyonn
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    well, I phoned kef today and asked to talk to someone about replacement drive units. I was told that they would put me through to the service department but he was off sick :) I'll speak to a hifi shop tmw, and probably call kef back on monday.

    dave
     
  10. fyonn

    fyonn
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    Right, I spoke to one of the dealers in Manchester who said they'd ask Kef for me. and then today I called kef myself.

    The dealer told me it would cost £50.

    Kef told me that the tweeter and midrange were seperately fixable (which surprised me, I thought it was an integrated unit). they asked which unit was broken to which I said I thought it was the midrange cone. they said that I could send them the entire unit, they'd work out what was broken, replace whatever it was (£34 for the midrange, £17 for the tweeter) and send it back. cost of labour included in the price of whatever component needed replacing.

    apparently the unit is soldered on though, so I'll need to de-solder it and re-solder it afterwards. never done that before.

    still, the latter option seems the best if I can work out how to remove the units from the cabinet without damaging anything.

    mind you, it's interesting though, Kef Reference 1 speakers used to list at £1600 was it? and the tweeter and midrange units add up to £50?

    It is rather tempting to get one of those wilmslow audio kits. I know someone who is a carpenter and could put it together for me too...

    dave
     
  11. philmate

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  12. fyonn

    fyonn
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    The only problem with ipl is that most of their kits tend to be for big floor standers. if I was to replace my kef references, I think I would be highly tempted to go for some wall mounted monitors and reclaim some floor space :)

    now... how do I get these drive units out of my reference speakers... :)

    dave
     
  13. fyonn

    fyonn
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    Just to finish the thread, I finally took my speaker into the shop and got it fixed and have it back. it ended up costing £60, £35 for the midrange unit, and £25 for the labour. I was happier letting them to do than risking it myself.

    haven't tested it yet as my Amp is being serviced for a fan replacement. they've had it over three weeks now and when I called, they told me they'll look at it next week *sigh*

    dave
     

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