Repir problem on Velodyne F-1800RII subwoofer speaker

[Bob F]

I have a Velodyne F-1800RII that failed. One wire that connects to the voice
coil on the speaker has disconnected. There is a tab on the tube that the voice
coil is wound on where braided cables attach to the voice coil wire. The braid
and connection is then sealed under what looks like white epoxy. That epoxy
separated from the tab it was one, allowing the braids to move and break their
connection to the voice coil.

To repair the connection, it seems I need to remove the epoxy from the tab to
get to the voice coil wire I need to solder. Does anyone have any hints on how
to proceed, which I imagine means removing the epoxy? I've thought about using
my heat gun with a small tube to direct the heat at only the offending area, but
don't know if this would be appropriate.

If I need to carefully cut loose the rear spider from the voice coil tube to get
enough voice coil to solder to, is it likiely that the coil is a bit below the
spider so I won't damage it while cutting the glue joint between the spider and
the tube?

 

[N_Cook]

I have a Velodyne F-1800RII that failed. One wire that connects to the voice
coil on the speaker has disconnected. There is a tab on the tube that the voice
coil is wound on where braided cables attach to the voice coil wire. The braid
and connection is then sealed under what looks like white epoxy. That epoxy
separated from the tab it was one, allowing the braids to move and break their
connection to the voice coil.

To repair the connection, it seems I need to remove the epoxy from the tab to
get to the voice coil wire I need to solder. Does anyone have any hints on how
to proceed, which I imagine means removing the epoxy? I've thought about using
my heat gun with a small tube to direct the heat at only the offending area, but
don't know if this would be appropriate.

If I need to carefully cut loose the rear spider from the voice coil tube to get
enough voice coil to solder to, is it likiely that the coil is a bit below the
spider so I won't damage it while cutting the glue joint between the spider and
the tube?

With good forced ventillation, excavate it with an old soldering iron and a
needle of some sort

 

[Phil Allison]

"Gareth Magennis"

I suspect the speaker most probably didn't fail, it was overdriven and was
broken by a Human Being.

** Still called a failure by most.

If you force the cone to move way beyond its limits,

** That should never be possible using electrical input alone. It is simple
enough to arrange things so the voice coil moves out of the magnetic gap and
loses most of the driving force before mechanical damage occurs.

However, some sub woofers are designed (?) with very long voice coils
rendering this precaution impossible.

Such woofers are bound to fail.

it will indeed eventually pull its own braids out to stop the torture.

** That should not be the case - easy to make the braids long enough so
any possible excursion is allowed

I gave up years ago trying to repair this sort of damage as it never holds
up for very long.

** Fitting longer braids is possible, done that a few times.

I had one job where the two braids had welded together half way along - the
maker ( Alesis ) had arranged to braids to vibrate towards each other and
touch if enough level were applied. Shortening each braid fixed it.

Mostly because the user is incapable of understanding that it was him that
broke it, so quickly breaks it again,

** Had one guy who repeatedly damaged his JBL K120s this way. He had them
in an open backed 100W Marshall combo amp and played BASS guitar through
them.

JBL specifically warn against doing this with the K120s.


...... Phil

 

[Phil Allison]

"Gareth Magennis"

I've seen a lot of Peavey black Widows with broken braids, mostly 15"
drivers from the 1 x 15 bass bins.

** Fatigue failures - not being yanked off by force.

There is only so much a piece of cotton cored tinsel can take.



.... Phil

 

[Bob F]

Epoxy is used to make rigid connections, not flexible connections. The
cone will flex and the wire should flex with it. The white glue should
be some sort of emulsion.

This really does seem to be epoxy. It is hard and brittle.

The glue should just peel off. You could carefully peel it with a
razor knife.

I tried snipping between the two leads, and separated the damaged one. The
covering came off in flying chips. Very brittle stuff. Unfortunately, the voice
coil wire coming out is broken off right where it comes out between the rear
spider and the tube of the voice coil, so I am going to have to separate the
spider from the voice coil tube a bit to repair it. It appears they used the
same glue to glue the spider to the tube.

This speaker is interesting. It has the normal front spider, and another at the
back of the magnet assembly. The two are maybe 5 inches apart.

This is more likely to fuch the speaker up royally. I wouldn't try it.

For linearity, the coil should extend well out of the voice coil gap.
Pull up the VC stub, and solder a bit of same gauge magnet wire to it
to where the braid goes in.

You are suggesting that if I can get a hold on the wire, I can just pull a
little loose from the coil to get enough to solder to?

Thanks for your help.