[NJARC] Speaker repair...

[Robert E Lozier]

Here is my two cents on speaker cone repair...

1. What kind if speaker are you needing to repair?  

Is it for Hi-Fi or is it for say... before 1937?  Or is it a cheap
speaker for an AA5?

There reason for asking is to assess the relative distortion by the
acceleration of a relatively asymmetrical massive patch on the true
conical portion of the cone.

If it is a Hi-Fi speaker, you want to keep the patch as light and RIGID
as possible....  If both sides of the tear are accessible, use Scotch
REMOVABLE tape on one side to hold the tear together.  You should be able
to get the tear to butt almost perfectly this way.  Then you can take
coffee filter paper (because it is very thin and porous) and cut a thin
strip to follow the tear line.  Glue it down with slightly thinned
Tite-Bond wood glue.  Once the glue has dried, you can then paint alcohol
or lacquer thinner around the edges of the Scotch tape (it won't affect
the wood glue.).  The solvent will wick under the tape and cause the
acrylic adhesive to get gummy and release...  Then take a Q-tip to rub
off the tape gunk... (easy)  Then just paint a ridge of the wood glue on
the back side of the tear.

The result is that you have bridged the tear without having introduced
much sonic distortion.  The bonded fiber dryer softener sheets are much
thicker and load up with much more glue to significantly increase the
mass of the repair.

If you are working to repair tears in the suspension between the cone and
the speaker basket, this mass problem is not so much a concern.

One new thing I have found for repair in this area of the cone where
FLEXIBILITY really is desired is flowable silicone adhesive.  Look for
Permatex Flowable Silicone Windshield & Glass Sealer - Here the dryer
sheets concept is useful although I would recommend you go to a local
fabric shop and look at the various weights of bonded polyester liner
material because I don't know if the perfumes, etc. in the dryer sheets
compromise adhesives.  I have even used a couple of strips of panty hose
out there on the edge to good effect!

Since the older cones are paper pulp with a lot of sulphur they really
are loosing a LOT of strength.  I've even started getting proactive in
some cases and just going ahead and painting on the silicone around the
outer suspension.  It soaks in beautifully.

Robert

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