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Old 4th May 2006, 07:54 PM   #1
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Question Paper Cone Strengthening

I have purchased a couple of PA FU15-4 subwoofers that have treated paper cones.
It has been rumored that there cones can fold and then rip apart if overloaded.
I am planning to run these subwoofers to there limits and am wondering what I may apply to the cones to strengthen them from tearing apart?

They are new and I have not used them yet. I have see another FU15-4 run to its limit and noticed that the cone is not running uniformly across the cone. It has a bit of a warble effect across the cone(thinking lack of stiffness).

If anyone has any idea how to help this problem without telling me to turn them down please lend a hand.

Also I have a PA15-4 for test purposes so don't be shy to give up your wacky solutions. Sound quality degration is not an issue.
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Old 4th May 2006, 08:05 PM   #2
qwad is offline qwad  Australia
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áfraid there is not much u can do without altering the drivers paramaters drastically 'thou on 2nd thoughts you could try reinforcing ribs on the back of the cone like tannoy used on some of their drivers of yore....... dunno if anyone else could chip in with more pos advice? GM? PLANET 10? good luck and cheers
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Old 4th May 2006, 08:18 PM   #3
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Thanks for your reply,
I have also entertained the though of reinforcement ribs on the rear.
Although I'm not sure what I would use material wise to do this.
Parameter changes are not a huge concern either being these drivers are only going to play from 60hz to around 35hz.
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Old 4th May 2006, 10:55 PM   #4
Ron E is offline Ron E  United States
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To be honest, you would have to see a failed unit to find the weak points. Willy-nilly reinforcements will only reduce sensitivity....which is perhaps a protection in itself

Most likely failure areas are coil and spider and the junction of coil and cone, not the cone itself.
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Old 4th May 2006, 11:10 PM   #5
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Apart from burned out coils, the most common failure mode I've seen in bass drivers is the splitting of the surround and the spider. Very few have damage to the actual cone.
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Old 5th May 2006, 02:01 AM   #6
lolojr1 is offline lolojr1  United States
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the problems i find while driving woofers to their max is usually tinsel leads melting

but

you are intrested in strengthening the cone i have seen a few people use fiberglass resin all it takesi s a thin coat on the cone and if you feel like it do the back side but dont get it on the spider or surround (of course)
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Old 5th May 2006, 04:19 AM   #7
Relax is offline Relax  United States
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Damar seems to stiffen cones, but have only seen it on smaller drivers, subs may not help enough.
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Old 5th May 2006, 04:27 AM   #8
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I have seen pictures and a video of the torn cones. It apears that it starts to fail by bending then tearing in the center of the cone between the spider and surround.
By the way its a daul spider design(top an bottom)
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Old 5th May 2006, 01:09 PM   #9
AMV8 is offline AMV8  United Kingdom
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Hi

I have tried varnish and acrylic glue ( which is stiff ) on parer cones. Both seem to work.

I have not noticed any detrimental affects for base/low mid but I have not tried on a mid range unit.

On the base unit the units were noticably stiffer after treatment and I believed provided a tighter base sound in a sealed box unit in comparison with non treated ut otherwise identical units. I did not take any sound measurements.

Don
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Old 5th May 2006, 04:58 PM   #10
AndrewT is offline AndrewT  Scotland
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Hi,
the concentric ribs seen on many bass drivers is, I think, a second layer of corrugations glued over the top of a paper cone. However this may be stiffening to reduce response anomalies at the high end of the frequency range.

The Tannoy type ribs are to prevent bending of the cone and extend well short of the voice coil former. Maybe a longer version that goes right upto the spider could help.

I have seen pics of horn loaded drivers that have destroyed the cone by repeatedly folding it due to lack of strength to push all that closely coupled air up the horn.

You could also add reinforcement from VC former to cone and a little beyond to help in that area.
I would try to minimise the weight added near the periphery of the cone. The forces needed to overcone the inertia of that remote mass must be quite big and worth avoiding.
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