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In Reply to: RE: A preservative for foam surrounds? posted by genungo on July 30, 2014 at 12:15:50
There is a way to preserve and "replace" foam surrounds.
Get some DAP Alex Plus caulk in the clear formulation, it may only be available in a large caulking gun sized tube.
Then, using an unused small child's water color paintbrush, squirt some caulk out onto a piece of clean cardboard or plastic sheet, and spread it onto the foam surround using the paint brush VERY gently and smoothly and evenly, and spread it out evenly as soon as possible. Work in small segments of the surround.
You will have to squirt out more small dabs to work with as you go, do not try to "use up" the current dab as it starts to dry.
The nice thing about the clear version, is that it goes on in a milky white color, so you can see that you are covering the entire surface of the foam, but it soon dries clear.
Spread a VERY thin layer, but with complete coverage, lapping onto the cone for approx. 1/16" PAST the edge of the foam as it goes down the cone,
and over-lapping onto the frame/gasket at the edge.
This will protect the foam, and when the foam does eventually rot (and it will), if you made the layer of Alex Plus even enough and with complete coverage, it will actually be a replacement for the foam at that point.
The secret is to get the layer as thin as possible, and yet still get complete and even coverage. This is usually achieved when you can not readily see the foam surround through the freshly applied white colored caulk, until it dries clear.
The other secret is to make sure you don't bulk it up at the edges, but rather, taper it down to nothing if possible.
Do NOT use the woofer for several days (5-7), even after it has dried clear, as the caulk takes days to fully cure.
Do not expose it to the sun, high humidity, or direct moisture either.
If you seal the remaining caulk in the tube well, it can be used for several weeks after opening, so you have time to do all of the foam surrounds you wish to treat.
If there is ANY doubt about how fresh the caulk is, DON'T USE IT !
Thickened caulk will end up needing too much pressure to apply via the paintbrush. At only several dollars a tube, it is worth it to seek out a fresher source of the caulk if the local store only has some old tubes available.
I strongly recommend practicing on a foam surround that is not a critical speaker component, such as from a cheap speaker from a thrift store, or a close-out driver from Parts Express, etc. You will have to develop a "touch" for how hard you can press on the foam before doing any damage.
Keep in mind that if the foam is already falling apart, you will NOT be able to use this approach, the paint brush WILL puncture or destroy the surround when you try to coat it. This technique will only work on relatively new (strong) foam surrounds, due to the amount of pressure that must be applied to coat the surround with caulk.
Oh, and BTW, the DAP Alex Plus is mold and mildew resistant.
Good luck!
Jon Risch
Follow Ups:
Weldbond is impervious to gasoline, oil, grease, salt, MOLDS AND FUNGI.
Thin it out a bit with water and apply with a soft brush, multiple coats are better than one heavy coat. Best product I have found for old foam that is going bad.
Goes on white, dries clear.
I have tried similar types of glues, essentially white glues (poly-vinyl types) and they typically dry too hard. The resultant stiffening of the surround can change the sound of the woofer, by altering it's frequency response and resonant frequency.
Some of these types of white glues can fail to fully bond to the foam surrounds, or may separate years later.
I have not personally tried the Weldbond brand for this type of use, so it would be interesting to hear some details about how many woofers you have treated in this manner, and for how long they have been in use since.
Jon Risch
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