Wednesday, July 4, 2018

Bullet Ear Buds

At one point, I had made a pair of these (not my video) :

But, since I use them most when traveling on aircraft, I wanted some that worked a little better with not-so-short wires, but that could make it through TSA without being confiscated due to the gun powder residue.

This resulted in a little different approach.  Here's what went into these :

  • Unused and unloaded .40 caliber brass cartridges, nickel plated
  • TDK EB760 Ear Buds for the drivers
  • A cheap pair of braided-wire ear buds from china (the color I wanted), primarily because the TDK wires are too short for me, even before cutting them out
  • A small chunk of round aluminum about a half inch in diameter
Tools used :
  • A cheap harbor freight heat gun
  • A small tool vise
  • Soldering iron
  • Small, round file
  • Drill bit just larger than the to0be-used speaker wire
  • My metal lathe with some collets (you can use a drill as shown in the video, but my experience was better with the lathe as explained later)

Once I had everything, I started by using the lathe to cut a brass plug that would press into the primer spot in the cartridge casing.  It was about 0.172 in diameter and pressed into it perfectly (make sure it's the right side when cutting the fake primer).

Place the casings into the small tool vise, take them over to the drill press, and (using the drill bit just larger than the wires) punch a hole in the side of the casing as shown in the video.  Use a counter sink to remove the raised edges and clean it up.  Do this for the other casing as well.

Next, I measured about 12mm in length from the back of the casing.  I need the line as I will put the casing into a collet with the primer side in the collet to both protect it during the cut, and also allow me to clean it up after the cut.  Make that cut, then bevel the outside edge.  Using a small, round file with a handle bevel the inside edge of the casing as well.  Because we are using un-spent brass, there is no expansion, which results in the casings being a little too snug in comparison to what is in the video, so we absolutely need a centering bevel on the inside.

Using the heat gun, heat all around the TDK ear buds until they come apart.  Don't get them too hot or you could destroy the drivers, and that is what we need out of them.  Once they come apart, cut the wire to release the speaker driver and the casing that holds it (and the rubber/silicone things that hold them in your ears).  The driver and the casing the driver sit in are what you want.

You now need the wire from the other ear buds.  Cut them free from the cheap ones, and then push the wire through the small hole from the outside of the casings to the inside.  Tie a knot to prevent them from coming out.

Use a soldering iron, release the old speaker wire still attached to the drivers, and attach the new wire that was fed through the casing side.  You may need to clear insulation on the new wire until you get to the colored speaker wire on the inside.  Solder them up like the old wires were (colored wire to colored pad, copper wire to the other pad).

Finally, I crushed the driver housing when I tried to press the housing into the un-spent brass.  I ended up using the small aluminum round after drilling a hole through it about a 0.25" in diameter, and them putting a concave surface.  I then took that with the driver housing and casing back to the small tool vice.  The round went over the top of the driver housing so I could press on the sides of the driver housing rather than the front, then centered everything up, and pressed them together.

I put the silicone parts back on, and tested them out.  They are pretty slick and pretty nice!  Great sound, cool look, and I HOPE it should get through TSA without confiscation.  Note, I have not yet tried to get these through TSA, so I don't know if they'll make it through.  I certainly hope they will.

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