Logitech X-540 5.1 speakers loudly crackle when volume moved up or down
There was no problem for a couple of months, then out-of-the-blue - when I go to change volume (up or down) the volume increases to an extreme yet variable level and is crackly & distorted until I stop moving the volume knob
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Sounds like it could either be the crossover circuit or a distorted speaker cone. The cone is the easy one to check. You need to check that it moves freely at all points. It sounds like you have partly done this, but you just need to make certain you went all the way around the cone checking for free movement.
However I don't think it is the cone, because of the slow way it acts up. That could be the crossover circuit. If you have a look at it and see either an IC or transistor looking parts, then I would have thought it would be one of them acting up - presumably getting hot!
If you can have the speaker outputting sound, with access to the crossover, you could spray these parts (one at a time if there is more that one) with Servisol Freezer spray. You simply wait till the fault develop then spray the suspect part. If it returns to normal you have located the faulty part. If nothing happens, wait till the coolant wears off then try the next suspect.
Places like Maplin stock the Freezer spray.
Sounds like you may have a blown (open) speaker. Remove the speaker and measure the DC resistance if you have a ohmmeter. Should read a little under the rated impedance (4 ohms). No ohmmeter handy? Touch a 9V battery across the speaker terminals, and you should hear a pop from the speaker. No pop then you have a bad speaker. Also the speaker should move freely when you push on it. Don't push the dust cover (the dome in the center) unless you like that dented look! If the speaker is indeed bad and you can't get an OEM (P/N: 363389-001) then an aftermarket speaker should (in most cases) work fine. Just make sure it is a 12", 4 ohms and rated at 250W RMS or greater. May actually be lower than 250W but better higher than lower. Good luck!
Rotate the volume controls. Does this cause the crackle? Try working the controls through several turns up and down.
Also check that the lights on the top are not solid red. This would indicate that the inputs are clipping (the input signal is too strong) or the volume is turned up too high.
If that doesn't solve it call Bose® Product & Technical Support at (877) 335-2673 (U.S. and Canada only)
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Hi Larry. From your description, it sounds like the voice coil of the woofer is damaged due to possibly overdriving the speaker, mainly playing the system very loud for an extended period. I would replace the woofer element. The woofer should be held in place with 4 screws. When removed, there will be 2 wires on spade connecters. Disconnect these and replace with the new woofer. Hope this helps you out.
The crackling could be due to a faulty wire or jack connection. If you have any other sound device (e.g. headphones), try connecting that one instead of the Z4 and see whether the crackling disappears (in which case it's the Z4) or not (in which case it's the jack or the computer). Could arguably be an EM or electrical interference, but you'd need a laptop running on batteries to check the second, and trying orienting differently the speakers to try checking the first.
The music slowing down means something's wrong in the computer: the Z4 are purely passive, they can't do anything to the music tempo. Try running an antivirus check or try Task Manager (or Process Explorer) and see whether anything's eating more CPU than it should.
Does the crackling and popping sound comes only from the sub, or from the other speakers too? Try switching of to check. I think that it is problem on volume control potentiometer. In that case all the speakers must sound crackling and popping. If the problem is only in the sub you have to check its connections.
Crackling is an unusual noise but typically indicates a bad capacitor in the amplifier board. This can be a rather costly repair but first we will go through basic trouble shooting steps.
Reduce the volume on the sub and see if the noise remains and changes with the volume.
Unplug the sub and disconnect interconnect cables. With both hands push softly on the speaker cone to move it in, let it back out and do this a few times. If you hear a scraping noise and some resistance your driver is misaligned and you need to recone or replace the driver.
Check all your interconnect cables, there may be a bad internal connection (usually causes pops and cut-outs).
Let me know how things workout. If it makes the crackling noise at all volumes and the driver seems fine then I would seek a professional to repair it, or replace.