Custom earplug speakers for motorcycling; strain relief
I had a set of Challenger custom earplugs with speakers made for me by Bob
Weis at The Earplug Company in Florida
in 2003. These are terrific for motorcycling, because they fit under your
helmet with no need for extra clearance, they block out wind noise better than
foam earplugs, and they give you high-fidelity tunes on the move. I use them
for motorcycling and also when I fly. The crying babies just don't exist when
you play your music through these. (You do have to peel one out to talk to the
flight attendants, though.)
I had a professional hearing-aid technician make the molds that I sent Bob.
For me it was $50 well spent: the instructions say to be sure to get "past the
second bend of the ear canal," but we found out my ear canal is unusually
straight. I would have thought I was doing it wrong when I didn't see any
Unfortunately, these earplug speakers are a little delicate and I'm a
little rough on them. Besides knocking them around occasionally in tank bags
and pockets, I'm forever feeling the wires tug on my ears (meaning the fragile
internal connection is also being tugged at) as I do head checks and
other maneuvers on the bike. I've had to have Bob repair/rebuild mine twice.
I started thinking about how I could add some strain relief. This page is
Adding strain relief to Challenger-C custom earplug speakers
Here's what the back of an earplugs looks like with no modifications.
The ridge in the center and the depressions above and below it are there so
you can "screw" the earplug in and out of your ear. You're supposed to pinch
the middle and twist the earplug so the bottom enters your ear canal.
(The red dot is a little stick that seems to be part of the manufacturing
process. It's not a tube, just a stick. Maybe Bob can tell me what it's for.
The one in the left earplug is a different color.)
I've found I don't use the ridge in the center for insertion or removal.
Instead, I hold the top and back of the plug and push/twist the bottom into
place, then push the top in so it fits snugly where it's supposed to, as
illustrated below. To remove them, I reverse the procedure. (Tugging the
earplug out using the wire is the fastest route to the repair shop.)
Since I don't use the pinch-bar or depressions anyway, I got to thinking
maybe I could use them for some strain relief.
Disclaimers and considerations
Attempting anything like this is sure to void your warranty with The
Earplug Company. Bob is a nice guy (he did my first repair during a
hurricane, for heaven's sake!) but monkeying with your earplugs and a hot-glue
gun is beyond reasonable when it comes to a warranty claim.
Bob also told me this: using adhesives on the wires can prevent him
from making repairs in the future. So think about that before you try
this. I believe I have this covered: I can melt the hot-glue off the wires
if they have to go back in for repair. (This is a reason to use hot glue and
silicone adhesive combined, instead of silicone adhesive for the whole job.)
This is a calculated risk that I'm willing to take.
Finally, Bob said he thought you could get enough strain relief with a
clip like you use on cell-phone earpiece cords - the kind that attach to your
collar. Or you can run the wire up over your ear and then down. But for various
reasons I thought these tricks wouldn't be effective for me.
Let's get on with it!
So here's what I did: I filled the little depressions with
hot glue, then made a loop of wire and rested the two halves of the loop in
the depressions. I held them there while the glue hardened around them.
Theoretically this should provide strain relief: a tug on the free end won't
pull on the delicate connection to the transducer (speaker) inside.
I tried to arrange it so there wasn't too much strain on the wire as it
leaves the ear mold and turns upward to the first blob of glue. I also made it
so the two blobs of glue aren't connected to each other. Otherwise, movement
at the free end would transmit to the other side of the loop, which defeats
There's just one problem: the hot glue doesn't stick to the outside of the
earplug. I don't know what those things are made of, but they're slick and
none of the adhesives I had handy would stick to them.
Bob told me that Permatex makes one adhesive that works. I think he was
talking about "Permatex O-Ring & Rubber Bonding Adhesive," which is Permatex
part number 40413. It comes in a little yellow bottle (1/3 oz.) with a tall
black cap and a black label. (Bob, if that's not the right stuff, please
tell me. If anybody else knows an appropriate adhesive, please tell me that
too. Use the feedback link in the left column of this page. Thanks.)
The idea is not to use the Permatex adhesive in place of the hot
glue, but in addition to it. Do the hot glue trick as described
above. When it has cooled and solidified around the wires, you can pop the
blobs (with wires running through them) out of the depressions. Now dab the
depressions with the Permatex adhesive. Put the solidified blobs of
hot glue back in where they came from, and hold until the Permatex cures.
Voila! Now your hot glue is itself glued into place. I figure I can still
get the wires free (if needed for repairs) by melting the top part of the
hot glue, while the rest is still secure. I can re-seat the wires later by
melting more glue into the right spots: the new hot glue will stick to the
old glue, which is still stuck to the earplug. Genius? Aw, shucks.
This all depends on whether the Permatex adhesive actually bonds to both
the earplug and the hot glue. I have not tried this yet, so don't
assume everything I've said is true!
Pedantic and wildly speculative financial
reasoning - stop reading now!
Bob says I might be ruining his ability to repair these in the future. This is a risk I'm willing to take. I figure (A) the earplugs
should last longer between repairs, (B) I can melt off the hot glue if
they do need to go back for repairs so he can do his thing, and (C) the amount of money on the
table is small enough that I'm willing to gamble. The worst case is a full
replacement at $160, with a low probability, as a bet against a reasonable
probability of saving one or more repairs at $70 each, plus hassle.
This page was last edited
April 26, 2008.