what glue to use for dust cap?

[fishline]

I have a speaker with the ScanSpeak 7" woofer that has the carbon fibre impregnated paper cone. The dust cap fell off recently. I tried searching online to see what kind of glue I should use to glue it back on, but can't find anything definitive. Can anyone here help?

[LineArray]

Hi fishline,

i have no experience with woven carbon
fibres ... most 2 component epoxy glues can be
mixed in a way to stay somewhat flexible
(strangely often by increasing the share of the
component called "hardener")

Such an epoxy "soft mix" would be my preferred
attempt after cleaning the two parts at the contact
area.

You may try the consistency of the (dried) glue on
a piece of paper first. It should stay a bit plyable,
not that hard and brittle consistency which is typical
for the usual epoxy mix.

For canny application you may use a "Tai Stick" e.g.
or a toothpick.

But i am sure there are more "glueing experts" in here
and we will find further proposals ...

[pinkmouse]

Well, I use just about anything handy for dustcaps. If you're not sure of accurate placement first time, then put the cap in place, then run thin superglue around the joint. If you're more confident, impact adhesive, epoxy, or as you have a paper based cone, even PVA. As Oliver said above though, don't use too much, and apply with a cocktail stick or similar, then put a weight on the cap to hold it down whilst it sets. I use an old 1 1/2" socket. Any minor glue runs can be smoothed with a wet fingertip.

[simon7000]

Normal speaker glue is made by a company called C P Moyen and is just called moyen by those in the trade. It is a high strength rubber cement. Using a rigid glue may cause the cone to crack where the glue saturates the fibers.

Moyen has a large number of volatile organic compounds that evaporate during drying. That way it leaves a glue joint that flows well but weighs almost nothing. It is also black the favorite color for loudspeaker drivers.

You can't buy the glue directly in small quantities directly, so a number of folks repack it in small tubes.

However as some folks are going greener a new glue has appeared that is a modified form of what woodworkers call "White" glue also known as Elmers or PVA! This glue remains a slight bit flexible after drying. So if you want to try another glue I would use yellow carpenters glue.

The trick is to place the speaker on a lazy susan then place the dust cap on the cone. Then place a weight on top of the dust cap. About 50 grams or 2 ounces should do. You spin the speaker as you apply the glue bead to get that nice smooth look. Then the hard part is not touching anything for 24 hours.

[Johnny2Bad]

When the dust cap on one of a pair of Energy Connoisseur C-2's I had came off (out of warranty) I called (the old)* Energy co and they told me use "Seal All" which is a fairly high VOC sealant in a tube. Very common in automotive shops because it's impervious to gas and oil when cured, so should not be hard to find. A bit tricky to work with but with some careful positioning it worked and it's been 10 years since. Poly cone speaker.

* Since being bought by Klipsch, I wouldn't expect any decent level of service from Energy ... I had a sub delivered with no power cord ... a simple problem ... and it was not a good experience.

They wanted me to box it up and ship it across the country, and wait for a replacement; that solution took 10 days to come up with, after concluding they could not possibly just mail one out, and not until after I was told by one service tech over the phone that it was "impossible" to not have a cord in the box, and implied I was lying (over a $3 IEC cord, yet). I just bought a new cord, and put them on the "Never Again" list, and naturally I share the story whenever appropriate, because apparently that's how they like it. I really did consider boxing it and costing them $150 for shipping both ways, but even with a company I no longer want to do business with that seemed too stupid an exercise to go along with.

[pinkmouse]

Originally Posted by simon7000

Using a rigid glue may cause the cone to crack where the glue saturates the fibers.

I've seen many hundreds of drivers returned for repair, and I've never yet had that failure mode.

[simon7000]

Originally Posted by pinkmouse

I've seen many hundreds of drivers returned for repair, and I've never yet had that failure mode.

I have! But my data base is probably tens of thousands. So I suspect that with the larger data base I have encountered more folks of less skill and intelligence who muck stuff up, than you have!

Recently we had to clean failed plating out of the magnet gaps out of 144 tweeters. A real pain in the... Oh yeah just out of warranty.

[pinkmouse]

Originally Posted by simon7000

...Recently we had to clean failed plating out of the magnet gaps out of 144 tweeters....

Nasty. Compressed air, brass shim scraper, or folded tape? Or all of the above?

[simon7000]

Originally Posted by pinkmouse

Nasty. Compressed air, brass shim scraper, or folded tape? Or all of the above?

Ah you understand the problem. All of the above plus stainless steel scraper. Interesting enough the folks I bought them from were using them and did not notice that about 1/3 of the tweeters had enough plating gunk keeping the voice coils from moving properly! Levels were about 6-10 db down at a few K!