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Fix it time for PC monitor speakers

Posted 16th December 2013 at 06:23 AM by fas42
Updated 22nd June 2014 at 07:35 AM by fas42

Bummer!! After mentioning that Brad's (bcarso) units were doing very nicely I swapped CDs while they were set to max. volume, doing a good job on a classical piece. Unfortunately, the new disk was heavily compressed pop, my mind was elsewhere, and I hit the volume control a second too late - everything's OK except the right speaker has dropped about 6dB in volume, ...

I suspect that some protection circuitry has tripped, but it's not resetting. Which means, unless anyone has a good idea otherwise, that I'll have to dive inside and sort things out. But, on the other side of the equation that may be an excellent thing to do, it will give me a chance to do some more adventuresome tweaking ...

Trouble is, I'm lazy ...
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  1. Old Comment
    fas42's Avatar
    Bit concerned at the moment - I may have overcooked the poor little amp in the speakers ... or it may be the colder weather we're having at the moment, causing longer times for the electronics to condition themselves. The sound at low volumes is very "fuzzy", the noise modulation I mentioned elsewhere is very bad, on both channels - is the DAC "wearing out"? High level sound is fine, I'm listening to a harpsichord at the moment, at max. volume, and there are no problems, earlier on I had high energy rock running also at close to max, and didn't pick any issues. But, with normal classical, say solo piano, with plenty of "space" between the notes the fuzziness was quite bad on softly played notes ... hmmmm, will see how it goes with more playing ...
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    Posted 14th July 2014 at 01:02 AM by fas42 fas42 is offline
  2. Old Comment
    fas42's Avatar
    Veeeerrry interesting - the problems I mentioned in the last post appear, I repeat, appear, to be caused by classic Rub and Buzz issues with the speaker driver. I might be on a learning curve here - on impulse, I started prodding the speaker cone while it was working at low volumes, basically distorting its shape, and pushing it around on its suspension, in directions it normally wouldn't feel forces acting upon it. Lo and behold, the fuzziness cleared up dramatically - so, for once, , the audible problems were of a physical nature, associated with the cheap construction of the driver.

    At high volumes, these problems evaporate, the cone is moving too vigorously for the sound to be audibly affected. This is the first time I've experienced, noticed this sort of behaviour, I'm wondering whether it's an age thing, the colder temperatures at the moment or an overall effect of driving them hard - any thoughts? In any case, I'll have a look around, see if anyone has mentioned such ...
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    Posted 14th July 2014 at 04:59 AM by fas42 fas42 is offline
  3. Old Comment
    fas42's Avatar
    Okay, lesson learnt. The physical manipulation worked, and stayed working. Next morning, from cold, here was the fuzziness again; so, immediately, reasonably energetic manipulation of the suspension with the fingers, and away went the fuzziness!

    Other people have mentioned that the voice coil getting pretty hot can cause it to deform, go out round; this might be the cause of my bzzz'ng - in any case, a good massage when starting irons out the noise issues ... all's good!!
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    Posted 15th July 2014 at 02:53 AM by fas42 fas42 is offline
  4. Old Comment
    wintermute's Avatar
    Frank, hopefully the lesson learned is "don't crank the amp to full volume!"

    It may be voice coil damage, but it could also be damage due to excessive excursion. The particular track you played may have some high level low bass that has driven the poor little speaker past it's limits.

    Tony.
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    Posted 15th July 2014 at 03:53 AM by wintermute wintermute is offline
  5. Old Comment
    fas42's Avatar
    Possibly the low bass issue, but it's filtered away below 100Hz, doesn't provoke the cone into movement. Unlike, the more ambitious looking Altec Lansing(!) unit I have here, which manfully tries to do something with lower than 100Hz signals, but just ends up sounding silly, !

    The interesting thing is that I have driven similar types of drivers to much higher SPLs over extended periods, the Philips HT speakers are very much out of the same mold, and zero issues - hard driving in fact cleans up some distortion artifacts in those ones. The difference there is that the amplifiers were more capable, had higher voltage rails, better power supplies; with the PC speakers it's easy to hear the onset of sagging of the PS, which I normally keep happening to a minimum; but, that behaviour may have played a part in the driver problem.

    Since all of this is an exploration, I'm not fussed about negative consequences, so long as understanding results ...
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    Posted 15th July 2014 at 04:22 AM by fas42 fas42 is offline
  6. Old Comment
    fas42's Avatar
    Have mentioned volume controls, on a number of occasions, and noted that many people have a horror of digital, or software versions of these. Anyway, having got the drivers back to good shape, I had to drop the volume back to almost zero, because my wife wanted to concentrate on some paperwork matters. The PC speakers now have no analogue pot, running at full gain, so the normal XP volume mechanism is doing it all.

    Yet, with a jazz piece on at the moment with vibes, cymbals, at a setting one of two notches above dead silence, the sound, and treble, is clear, rings nicely across the room, and still is completely intact with my ear against the speaker - so, where are these "terrible digital volume control problems" ...?
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    Posted 15th July 2014 at 04:43 AM by fas42 fas42 is offline
 
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