jbl 2205a cracks in sorround flappy drivers - diyAudio
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Old 11th January 2013, 09:25 AM   #1
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Default jbl 2205a cracks in sorround flappy drivers

hey guys got a pair of jbl 2205a hear that have been running as part of my system for years with no probs, untill i pulled them out recently after 6 months of storage in a garage, to hook em back up as i have moved house since now and i had them in the lounge room up untill we had a couple of 40'c days summer heat here in melb australia but to top it of the idiot im liveing with left the central heating on set at 48'c blasting through the whole house not only these but a couple of my other twelve ince woofers stuffed up aswell but mainly these jbls i took the fronts of the cabinets and held them up to the light and you can basicly see through all the tiny microscopic sqaures in the rippled cloth sorounds(the jbl enthusiests should be familure with) not to mention a few cracs , so im guesing thats way there flappy sounding to and clipping at low volume there running of a 400 watt power amp at 85hz cut down with electronic cross over ...what do you guys sugest useing to dope the surounds i already have some selleys kwik grip wich is watter based and drys soft and rubbery ive used when reconeing and works great but what would any you pro's out there recomend for my style off sorounds here they are anyhow ..Click the image to open in full size.
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Old 11th January 2013, 01:15 PM   #2
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Use Weldbond.

Thin it out a bit and build up layers.

I was able to extend the life of some really damage 2205s in a high-power club install, several extra years worth.

Products | WELDBOND (where to buy)

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Use bits of rice-paper if you need some filler to patch up missing chunks.
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Old 11th January 2013, 05:00 PM   #3
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I'd ping a not to far away pro sound recone shop.

They have a variety of "treatments" designed for the edges of drivers.

Also a bit depends on what these cracks are, and what your edge is. Is it paper or cloth? Can't really tell from the photos posted.

Usually on paper they only treat the outside. It's not a bad idea to treat the inside too...

I'd stay away from anything that is hardening, or that is PVA based glue. I have no idea what is in the Weldbond.

In a pinch, there is "flowable" silicone rubber, it can be brushed on. It is sold for, among other things, automobile windscreen (front glass) sealer in autoparts stores. Dow chemical also makes it.
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Old 11th January 2013, 07:44 PM   #4
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ill have a look at this weldbond stuff ...they are all original and have never been touched, almost 40 years old, my pride and joy ,dont care so much about the other four 12 inch subs he ruined mostly cut about these,but i got them off a mate who got them from a picture theater when it closed down back in the "70"s here in melbourn, this theater was renowned for its "sensation sorround sound" and had many people either bring up there lunch or run out almost about to from all the bass they ran 20 off them in a small hall with wooden seats and flaw i had to make the boxes aswell .. the idot i live with is to lazy or has no apreciation for something like this.. all he did was open the windows in his room and go to sleep ..they are cloth sorrounds fairly solid and look like they may have had something doped on them originaly to stiffen em up a bit any way here is another pick a bit closer
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Old 11th January 2013, 08:19 PM   #5
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Thinned with water, Weldbond soaks into the pores of the surround and the water then evaporates. It is also used on foam surrounds, and paper surrounds and the full cones. It is not recommended for rubber.

Click the image to open in full size.

These RCA have a paper surround. When they were removed from service circa 1980 there were chunks that were missing out of the surround and the cones were very brittle. Installed in the late 40s, they were on there way to the landfill by 1980. One thinned out coat to the full cone and edge, then some patches and two thicker coats on the edge brought these back to life. They are in use now in a small theater in Kansas.
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Old 11th January 2013, 11:04 PM   #6
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I wonder if silicone will work as well?
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Old 11th January 2013, 11:07 PM   #7
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well ok, it soaks in, but what is it??

I'm not saying it is no good, I'm wondering what sort of "glue" and concrete bonder is going to remain flexible...

... I am saying that they make stuff to do this job in the speaker industry.

I've patched surrounds too... rice paper, other paper, cotton gauze, other stuff depending on what it needs.

Wonder if there is an MSDS on the Weldbond that will tell what the chemical makeup is? I shall search now that I am getting interested.
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Old 11th January 2013, 11:14 PM   #8
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MSDS calls it a PVAC, Polyvinyl Acetate emulsion.

They apparently can be constituted for a variety of applications and different adhesive properties.
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Old 11th January 2013, 11:18 PM   #9
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"I wonder if silicone will work as well? "

No, I've tried that too. Weldbond gives much better results, is safer to use, easier to clean up, non-toxic, and is less expensive too.

Weldbond® is a PVA adhesive . (Poly Vinyl Acetate based adhesive)

http://http://www.weldbond.com/files...aladhesive.pdf
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Old 12th January 2013, 04:44 AM   #10
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hey i manged to stumble across that weld bond stuff at the hardware store when buying some stuff to dope the vc"s on a diferent set ,im curently testing it on some paper wattered down at diferent thinning rates ...ill let all know how it goes but so far seems alot like the stuff i mentioned above goes on the same and goes tacky after a little bit soft and rubbery feel when dry

but not sure if its avail worldwide its an australian product ive had great success with bonding surrounds to cones and cone to frames strong flexible in thin coats i even had to pull one speaker apart that ran for 6 years and was still like softish rubber and was able to pry it apart easily enough without solvents or damage it drys to what id say would be inbetween rtv silicon and latex im geusing this weldbond is going to be very similar ,," hopefully "caus it only costs half as much
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