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View Full Version : Repairing weak spot in 2242hpl cone



KenWH
06-28-2006, 11:27 AM
I tried searching here but couldn't find anything.

I just got a couple 2242's off of ebay. Once they arrived I noticed one had several scratches/gouges in the cone like a cat went to town on it. Well one scratch is pretty deep(almost totally through the cone) and caused a weak spot in the cone. Is there any thing I can do to add strength back to to area? Maybe lay in a thin layer of fiberglass over it?

Thanks in advance for the help,
Ken

scott fitlin
06-28-2006, 06:52 PM
A little GE clear silicone will work for small tears such as you describe, and all you need is a caulking gun to apply.

subwoof
06-28-2006, 08:01 PM
Silicone will NOT strengthen the cone at all and will make it impossible to do it right later.

The cone is a layered paper compound and you should use some strong epoxy to seal the rift. Call a JBL reconing service center and ask them what they use.

No matter what you do the mass in that area will be greater and if you pound them hard, the original weakness will expand.

sub

Mr. Widget
06-28-2006, 08:13 PM
Silicone will NOT strengthen the cone...I agree. Nothing will be as strong as the original fiberglass impregnated cone, however if you want to give them a whirl before spending the money on a proper recone, I'd use simple PVA "white glue". It will soak into the paper giving you a strong bond and remain slightly flexible. It is also quite light once the water has evaporated and the glue is cured.


Widget

KenWH
06-28-2006, 09:00 PM
Thanks guys. I think I'll try some simple white(elmers)glue and a layer of newspaper on the back side. My nephew built a school project(made a large dragon fly) and used newspaper and white glue over a wire skeleton. Once it was all dry it was very rigid. I was shocked at how strong it was yet still very light weight. Since it's a fairly small area that's damaged...i'm hoping it will do the trick.

Thanks again for all the suggestions.

GordonW
06-29-2006, 09:19 AM
Should work. Newspaper/paper towels and Elmers glue, is the standard "audio hobbyist" method of repairing a damaged paper cone... been around for many years. Not as good as a factory-fresh cone, but probably will work with no subsequent problems.

Regards,
Gordon.

KenWH
06-29-2006, 09:42 AM
I did the repair early last night.

Other than the color difference...the newpaper/glue combo looks and feels just like the original cone material. I can't even feel the edges of the paper patch. I got them mounted and ran the 2242's through a pretty good work out a few minutes ago. It's my first time hearing the 42's and needless to say...they are a nice step up from the 2241's that originally came in the enclosure(4642a).
Best part...the repair seemed to hold just fine:applaud: .

Now I just need to move the 41's over to my 4688....I hope my neighbors like bass.;)

Thanks again,
Ken

Baron030
06-29-2006, 11:25 AM
If you should need to re-enforce that weak spot further, don't use the heavy automotive or boat repair grade of fiberglass. What you want is the kind of fiberglass that is commonly used to make radio controlled model airplanes. If you search out hobby shops that carry model airplanes, you should be able to pick up a small package of fiberglass mat for only a few bucks. The stuff you what has about the same thickness as a single sheet of newspaper. And it should weight only about ¾ to 1 oz. per square yard. The only additional piece of advice that I can give you is this, don't get heavy handed with amount of glue your using. Fiberglass mat likes to suck up a lot of glue. So, you only what to use just enough glue to stick fiberglass mat to the speaker and no more.

Baron030

KenWH
06-29-2006, 11:46 AM
Thanks for the info Baron.

I've made a few sub/speaker enclosures out of fiberglass. I usually use the heaviest chopped mat I can find.:p I didn't even know about the light weight "hobby" glass. For the speaker repair, would I use the two-part resin or would it be better to use simple white glue instead?

-Ken

Baron030
06-29-2006, 02:41 PM
Hi Ken
I would still use "White Glue" for any speaker repairs. If for no other reason then, it could be removed with a little water and careful rubbing.

I know that what I am about to say takes things way off topic.:offtopic:
(Why this could even be a good idea for whole new discussion thread?)

But, Yikes! Building sub/speaker enclosures with heavy chopped mat.
Wow, that’s a box I would not want to lift, it must weight a ton.
You probably already know that fiberglass gets its rigidity through the use of shape and wall thickness. With curved surfaces being more rigid then flat ones. And that each time you increase the wall thickness, the rigidity increases by its cube. So, if the wall thickness is doubled, then there is an 8 times increase in the rigidity. But, before you start breaking out even more chopped mat and resin. In the future, please look into using fiberglass/foam composites. If I wanted to build a speaker enclosure out of fiberglass, I would start with a 1" layer of Divinycell foam and then lay down just two layers 6-oz. fiberglass cloth on each side. The resulting composite would be a very rigid enclosure and it wouldn’t be a ball buster to move.
Oh, a good source for Divinycell foam is www.fiberglasssupply.com (http://www.fiberglasssupply.com).
Since, this company caters to hobbyist’s making surfboards, they do accept small orders.

Baron030

KenWH
06-29-2006, 04:22 PM
He he I may have overstated my use of fiberglass. I've used glass to mold in speaker/sub baffles in odd shaped/tight area's of car trunks etc. I've not built a whole box totally out of fiberglass. But I'm bookmarking your link cause unlike some folks...I actually enjoy working with fiberglass and plan to expand my projects in the future.

If I may brag a little:p ...my favorite glass project was for my 7yr. old Nephew. I made him a light weight boombox for his family to take to his XMA karate tourney's. They fly all over the country and they always had to lug around a large poor sounding battery powered boombox. Well I bought a little t-amp from partsexpress and a pair of 6.5" 2-way kenwood car speakers from crutchfield. I basically mounted the speakers to a thin piece of 1/4" hd fiberboard and formed a glass box around the baffle and the "amp rack". The whole thing tips the scales at 10lbs batteries,woofers and all with 2/3rds of that weight coming from the woofers themselves. Overall it's 5lbs lighter than the boombox,smaller overall in size, plays several times louder and sounds way better. My nephew loves it. He can actually hear/feel the bass in his songs now.

SIDENOTE:
Those little t-amps are pretty decent sounding amps. I wish I had bought the ac adapter(amp makes a little more power that way) as just running it off the aa batteries it sounded pretty good connected to my old Klipsch RF-7's.

Baron030
06-30-2006, 12:08 PM
Hi Ken
I'm glad to hear that you enjoy working with fiberglass. Sure, fiberglass is messy, and it's smelly, and you end up itching like crazy. But, God, how I do love this stuff. Your lightweight boom box project is a perfect example of how fiberglass can help solve a problem. Fortunately for me, I got introduced to stuff from an old timer, who worked on Corvettes and Fiberglass Boats for a living. So, I have ended up learning a lot about fiberglass from a real expert. Other than one small car audio project, almost all of my fiberglass projects have been involved with making telescopes. Astronomy is my other very expensive hobby.

Rather then pull your original "Speaker Repair" thread even further off topic. Maybe, it would be better for someone to start a whole new DIY fiberglass enclosure thread. I will be happy to chime in with useful information, comments, and other crazy ideas that might be helpful. :)
Baron030