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Cause of speaker surround separating from driver

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itskabini View Drop Down
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    Posted: 04 August 2021 at 1:45pm
When I bought my sound system a lot of the subwoofers had blown drivers, although the damage seemed a bit different to what I've seen before. The surround seemed to be tearing away from the cone itself at various points around the edge. The speakers seemed to still work OK however, voice coils were fully functional although they didn't sound quite right, and on removal they seemed a lot darker than a fresh one.


I initially thought this was likely due to overexcursion causing damage, although looking at a winISD prediction, the maximum excursion should have only been about 17mm to a xlim of 22mm. 

The signal getting to the drivers was likely heavily compressed however due to the processing that was used with the system before, so this could have caused problems.

I've also had someone suggest that this could be damage due to humidity, as the speakers were used in a nightclub that probably wasnt that well ventilated.

What's people general opinion on the problem? I'm now running the system with some very conservative limiters, but if excursion wasn't the problem before then I can open them up a bit.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote fatfreddiescat Quote  Post ReplyReply Direct Link To This Post Posted: 04 August 2021 at 3:49pm
Most likely over excursion, are you using a highpass filter?
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itskabini View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote itskabini Quote  Post ReplyReply Direct Link To This Post Posted: 04 August 2021 at 3:50pm
The system was set up with a highpass filter at 25hz before, I'm running this a bit higher now to be safe.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tinnitus Rex Quote  Post ReplyReply Direct Link To This Post Posted: 04 August 2021 at 3:52pm
The edge suspension can rot and become brittle after time. The edge support,spider and leadoffs are the only mechanical parts of the cone and have to survive trillions of movements .The highest stress point is where the cone meets the fabric edge support (as your photo demonstrates) there are four places where the weave of the fabric joining the cone cross at a + rather than an X. The + parts are weaker due to having only one thread direction taking all the stress.
If a small air hole occurs in the fabric edge  the box pressure soon blasts a bigger one.
it is difficult but not impossible to fix using contact adhesive and fabric patches or replace the edge (pita)
The edge support and the spider have to provide the spring force that brings the voice coil back to its zero reference point ,these can stretch and lose their spring over time. The "tinsell" leadoffs often need replacing  in time ,All these factors decide is it worth fixing or reconing.
"couldn't we just like... use headphones?"
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itskabini View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote itskabini Quote  Post ReplyReply Direct Link To This Post Posted: 04 August 2021 at 4:01pm
I guess this could have just been normal wear and tear then. They would have been getting used hard multiple times a week for years.

I've already reconed all the ones with visible tearing, was just trying to ensure it doesn't happen again
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Earplug Quote  Post ReplyReply Direct Link To This Post Posted: 04 August 2021 at 4:21pm
"and on removal they seemed a lot darker than a fresh one."

That's most probably due to HEAT! The obsession with trying to squeeze every "Watt" from the speaker - and actually loosing dB's - and lifetime due to overheating the things.   Dead


Earplugs Are For Wimps!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote APC321 Quote  Post ReplyReply Direct Link To This Post Posted: 04 August 2021 at 7:29pm
Originally posted by Tinnitus Rex Tinnitus Rex wrote:

The edge suspension can rot and become brittle after time. The edge support,spider and leadoffs are the only mechanical parts of the cone and have to survive trillions of movements .The highest stress point is where the cone meets the fabric edge support (as your photo demonstrates) there are four places where the weave of the fabric joining the cone cross at a + rather than an X. The + parts are weaker due to having only one thread direction taking all the stress.
If a small air hole occurs in the fabric edge  the box pressure soon blasts a bigger one.
it is difficult but not impossible to fix using contact adhesive and fabric patches or replace the edge (pita)
The edge support and the spider have to provide the spring force that brings the voice coil back to its zero reference point ,these can stretch and lose their spring over time. The "tinsell" leadoffs often need replacing  in time ,All these factors decide is it worth fixing or reconing.


+1
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 4D Quote  Post ReplyReply Direct Link To This Post Posted: 04 August 2021 at 10:39pm
cone damage from mechanical wear & tear & old age whilst a heavily compressed signal being not far off straight DC is quite likely to nicely toast voice coils 
DMZ. "The bass was intense. Girls were literally running up to stand next to the subs"
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