Here is the link for the DIY repair I mentioned in the previous post. My subs aren't dry rotted to the point that they are falling apart, They are cracked just above where the connect to the cone with a few 1/8-1/4 holes in the same areas. I figure that it's worth a shot and if it works then I have saved some money.
Cracking foam surround patching help! - diyAudio
Post #5
I am not a professional speaker repair person, but I did not want to hassle with finding and replacing the surrounds, and I wanted to hear my new speakers right away! The high end was OK, but the woofer surrounds were in pieces, but still holding the cone in alignment. It was an odd value 28 ohm woofer with rotten foam, so I figured it was going to take awhile to find and get a replacement, so I elected to try a repair first, and then start the search for a replacement. (that was 1 1/2 years ago)
3M makes a black contact cement adhesive for door trim. The black is nice since it blends in somewhat with the original colors. I was able to buy it at an industrial supply in a medium size tube. It was recommended somewhere, maybe a speaker vendor, as the best adhesive to glue rubber surrounds to polypropylene cone material. Search for Dynaudio surrounds. Someone, somewhere mentioned the door trim adhesive. Most just said the white glue was OK but it does not seem to adhere well to the poly cone material.
I diluted the contact cement with MEK, in small batches, maybe a teaspoon or so, and then with a small model brush, painted the mix onto the foam. Eventually, after a few applications, on both sides, the surround was basically now rubber. The first coat was diluted quite a bit, and it soaked in. When the first coat dried, there was a noticeable improvement in the strength of the foam. Towards the last coats I did not dilute as much - just enough to allow smooth brushing.
The foam in my case was so bad that the weight of the wet adhesive would cause additional breakthroughs. Several of the real bad spots I laminated on a single thickness of cheesecloth, to hold it together till the first layer of adhesive set. I suppose patches of very thin similar foam would also work, maybe better.
The end result does not look great, and it had to change the characteristics, but mine was down firing. It seems to sound fine. Someday it will be properly repaired or replaced.
If your foam is in better shape, a single application may be enough, and not add to much additional weight. It shouldn't hurt anything, and is cheap, and I can still remove the repaired surround if I find one that is a perfect fit, or piece one close in size together, so not much to loose except a 9.00 tube of adhesive, which you will need anyway if you have poly cones, and a bit of time. It actually was completed during one weekend, so went pretty quick.
good luck,
Dave
Post #7
Here is the stuff.
It is actually Loctite 30540. I got the MEK at the local hardware store.
Judging by the condition of my "repair" after 1 1/2 years, I would say it is going to hold up for quite some time. The rotten foam is basically encapsulated by the rubber. You might also try regular contact cement like "Goo" from a hobby shop, but some products may remain tacky. This stuff feels like rubber when dry.
Loctite® Black Contact Adhesive, distributed by R.S. Hughes - Industrial Distributor - Tapes, Adhesives, Abrasives, Safety, and Electronic Products
( I actually used this Loctite product)
Shop 3M: 3M Super Weatherstrip Adhesive, 08008, 5 oz tube, Black
(this is probably the same stuff by 3M, and I found it listed in auto parts shops)
Post #11
I ran into this problem a number of years ago. After much investigation, I ended up using modified acrylic latex caulk from the hardware store. If I recall correctly, it was DAP brand, though I’m not 100% certain which one I used. DAP ALEX PLUS Clear would seem a likely candidate.
The material I used was milky white as a liquid but dries essentially transparent on the surround. Add enough water to thin (not too thick, you want the solution to penetrate the foam), then paint the surround repeatedly with thin coats allowing sufficient tine to dry between applications. If accessible, do the back side of the surround also. The result is a tough, flexible film which impregnates the deteriorating foam. I used this method on several Infinity subwoofers which are still in daily use some eight years later.
Not having performed any before or after measurements, I can’t document any changes to the driver performance, but empirically speaking, the coating does not appear to have significantly altered the drivers parameters.
Keith
assive
