Muffled Centre Speaker?

Discussion in 'Home Cinema Speakers' started by Kootuu, Mar 1, 2014.

  1. Kootuu

    Kootuu
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    Hi Guys, I've got an intermittent issue with my centre speaker (Kef iQ60C) that I'm having a hard time diagnosing.

    I've got my receiver (Pioneers VSX-921) set to Auto Surround so it changes depending on the source but I'm noticing that from time to time a Dolby Digital source will be working fine one minute and the next the Centre speaker sounds like it's underwater or blocked – you can hear a faint sound of the dialogue, but it's very very low and sounds like they are mumbling.

    If I switch the receiver to Stereo you can hear it all fine as dialogue is coming out of the 2 fronts. If I then switch it back to Auto Surround it suddenly fixes the issue. Any ideas what could be the cause of this? Is it my Speaker? Amp? Cable?

    Because it's so intermittent I can't find a good way of testing it :/

    Edit: Forgot to add that this has been happening since we had a power cut a couple of months back.

    Thanks,
    Chris
     
  2. KelvinS1965

    KelvinS1965
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    I deal with intermittent faults at work sometimes, so you have my sympathy...

    I don't know how practical it is, but you could try swapping over the cable from your centre speaker and say the left speaker at the AMP end, so that this tests the speaker and it's cable. Of course it will sound odd like this (unless you can move the two speakers around physically as well), but if it's just so you can check if you lose speech after a while then it will work. It just depends how often the fault occurs I suppose, compared to the inconvenience. It could even be that the fault stops completely which might indicate that you had a poor connection at the amp end of the speaker cable, before you moved them.

    If the fault moves to the left speaker, then this at least confirms it is the amp. It could be a relay inside the amp dropping out and breaking the connection, so that you are only hearing the speech 'bleeding' through the left/right speakers (that 'underwater' effect you mention). If the amp continues to display the correct sound mode during this fault then it seems less likely to be an issue with the DSP/auto switching. Of course whether it's a relay or DSP issue (or some other internal connection failure) then the amp needs repairing/replacing anyway, but at least you've done all you can checking cables and speakers to isolate where the fault lies. You can then either live with the work round of manually changing the setting on and off, or repair/replace the amp.
     
  3. Kootuu

    Kootuu
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    Thanks for the reply Kelvin, so it sounds like you think it might be more an issue with the Amp than say a blown or damaged tweeter within the speaker itself?

    Will switch the speakers around and see what happens, the problem is I can go weeks without it being an issue so very hard to replicate :( The receiver is still under warranty so I guess I could also just take it back to see if they can identify any issue with it.

    Thanks,
    Chris
     
  4. KelvinS1965

    KelvinS1965
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    I think it's unlikely to be a blown tweeter as you'd hear it all the time, but swapping round the speakers/cable should confirm where the fault lies. Weeks between faults makes it harder too; it's bad enough when I get a customer with a fault that only shows every few hours.
     
  5. BlueWizard

    BlueWizard
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    Can you or anyone give an expanded explanation of "Auto Surround"?

    I'm always wary of "Auto" anything. Do you have other surround mode where you can absolutely set it, thereby buy passing the "Auto" aspect. I'm not that big into Surround Sound so this "Auto" feature is new to me.

    One thing you can do is switch the wires on your speakers. That is use the Center Channel amp to drive the Front Left Speaker (as an example). Then have the Front Left Channel drive the Center speaker. If the problem is the amp, then the Front Left Speaker (now on center channel) should experience the same problem.

    However, if the problem is the speakers itself, then the problem should stay with the speaker.

    I'm suspecting the problem is with the amp, but I'm not convinced that the amp is truly faulty.

    Just one possibility.

    Steve/bluewizard
     
  6. Philip4242

    Philip4242
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    Before you start swapping cables about, have you thought of doing a 'Factory Reset' on the amp ?

    All it takes is a power glitch to upset the 'computery' bits in an AV amp, and who knows what might randomly happen !

    Powering-off is often not sufficient, as various settings are stored in non-volatile memory.

    A Factory Reset will clear all these settings, giving a fresh start for an Auto-setup.
     
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  7. BlueWizard

    BlueWizard
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    Excellent point from Philip4242. Absolutely do a Reset of the system. Especially since this seems to have started with electrical glitch.

    Good thinking on Philip's part.

    Steve/bluewizard
     
  8. Kootuu

    Kootuu
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    Hi Guys, thanks for all the advice will definitely give the factory reset a go tonight (need to dig out the manual!) but otherwise will try not using the Auto setting which from what I can tell outputs the correct format (Stereo, Dolby 5.1, TrueHD, etc.) based on the source. Right?

    Thanks again for all the tips fellas.
     
  9. Philip4242

    Philip4242
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    As with many other manuals - available on the web from the manufacturer.

    VSX-921 - Pictures, support, downloads - Pioneer UK

    Also a firmware update.
     
  10. quatter

    quatter
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    With My LX82, Auto Surround defaults to the last setting that you input. Having selected auto surround you then need to select the 'standard' key to input your preferred setting. It should then default between DPL (orDPL11) or DD depending on the signal received.
     

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