This is a great mod to try if you want to enhance cheap earbuds/earphones or your cord is already broken somewhere (hopefully at the plug end, because it's usually difficult to figure out how to take apart the in-ear units if no one has already documented the procedure).
Essentially, to proceed with this mod involves re-making the Y-junction where the common cord splits left and right. Having to cut and rejoin wires possibly degrades audio quality¹. It's likely that you'll notice one of the binaural output signals being noticeably weaker, especially as you lower the volume on your audio source, but this condition is common on cheap headsets to start, so this is why I do not recommend you try this on expensive gear and fail to like the results.
However, it's possible to not introduce more points of electrical resistance, by choosing to redo the existing solder points at either end, if you willing to perform a more laborious rebuild.
As another caveat, depending on how discriminating you are about your listening experience with in-ear headsets, this mod might not be worth it. Paracord, being made of rigid nylon, will audibly and crisply chafe (therefore transferring this sound to your ears), but the use of a clip should reduce this by keeping it from sliding against the sides of your face and any hard fabric you may be wearing.
See the last step of this ible for more notes.
Step 1: Gather Materials
• Paracord of your choice. I assume the larger the diameter the less prone it is to flexing and therefore tangles/knots, but there isn't any significant diameter variety.
• Sacrificial earphones or earbuds with a cord thin enough to be easily thread through the outer jacket of paracord. The ones used here are Sennheiser CX55 In-Ear Headphones.
• Heat Shrink Tubing of various diameters
• Electrical Tape; depending on your earphone design you may have to tape the ends so that the heatshrink tube does its job of holding onto something with the paracord in place.
EDIT: Actually, super glue is more effective than tape. After a few months tape will tend to fail. I guess some sort of plastic cement might work, too.
• Small alligator clip (optional). I recommend clipping the cord to a shirt so that the headset remains in the ears and the cords freely contacting only air, despite whatever odd looks you may get from onlookers.
• scissors or knife
• wire cutters/strippers
• lighter (preferably a butane, torch type)
• soldering iron, flux, solder
Step 2: Cut Cords
Once you've decided what lengths you want each of the segments to be, cut your earphone cords into three pieces. Because I like the existing cord lengths of mine, I cut it at the fork.
Cut sections of paracord to match the earphone cord segments.
It's good to cut a little more than what you need because it will compress after sleeving. Based on my mod, I needed 15% more for the longest section. YMMV depending on the existing wire characteristics.
Gut the two shorter sections of paracord (remove the inner strands).
Step 3: Sleeve Cords
The longer piece can be more quickly done by hitching the cord to the inner strand(s) you saved, and pulling most of it through.
Unfortunately I haven't bothered to research the best way to do this without the temporary joint of old gut and new gut at some point breaking apart. I just use tape, and when it comes out alone I push the remaining cord through using peristaltic action: push the tip forward a tiny bit to form a compression of sleeve while squeezing behind the tip, then squeeze the sleeve around tip, and pull the compressed sleeve backward, undoing the compression (repeat). It takes a while if you didn't get most of it already pulled through.
Once you've sleeved them, use some heatshrink tube on the ends of the ear units and plug to tidy things up.
Note you may need to hold the paracord ends underneath in place using electrical tape if the design flares out and will not accommodate heatshrink without it slipping off.
Addendum 2010 06 22
Anyone want to experiment with also feeding a semi-rigid monofilament/fishing line through? I imagine that knot resistance could increase by doing so.
Step 4: Integrate a Clip
I use a small alligator clip that's intended for electronics. To make it look nice and to keep its metal teeth from biting into shirt fabric, cut a piece of heatshrink tube for the upper half. Make 3 cuts in the shape of an 'H' to slip into place, covering both jaw and handle. The 'H' cut is as high as the clip is wide, and as wide as the clip's hinge area is long. I've added a primative illustration.
Apply heat, then repeat for the bottom half, this time using a piece of heatshrink tube that is of a sufficient diameter to wrap around two sections of paracord and the bottom half the clip.
Step 5: Rejoin Wires
I oriented mine so that the clip is "jaws up," since it will be clipped onto my shirt and the weight of the slack cord to the audio source will pull downward, assuming gravity pulls downward.
Carefully strip the outer insulation revealing the inner strands of wires for your earphones. If the insulation is more rubbery than it is plasticky (tough to sleeve!), it's enough to cut the insulation halfway and stretch it until it breaks.
It's usually that the gold wire is common/ground, red is the right channel, and green is the left channel, and that it's enamel-coated, stranded wire. What I do is carefully use my lighter to burn away the enamel. Blow out the fire before it strips away too much wire!
You only need around 1/4" (6mm) exposed.
Slip on heatshrink tube long enough to cover the exposed copper. Then it's a matter of matching wires, twisting the exposed copper ends together tightly and tinning them with solder.
Meanwhile, plug the earphones into an audio source to check that the soldering works. As long as your soldering iron operates by emitting only heat, it should be safe to do this.
Once satisfactory, slide the heatshrink tubes over the solder points and shrink them.
Step 6: Finish the Y-Junction
I'm uncertain of how best to join the paracord ends together since I failed to melt the ends before they got frayed, so this is what I did:
To join the paracord here, what I did was take an inner strand and wrapped that around. I then used my torch-style lighter to melt it to fuse it together some. That wasn't very effective so I then coated it all with epoxy. I chose too small of a diameter of heatshrink for my clip, so i hurriedly slipped that over before it cured. But I fixed it as you can see, using some bigger heatshrink.
Step 7: Use
Feel free to comment on your experience.
More Trivial Notes/Findings:
¹ I'm not so sure now that audio quality is noticeably reduced. I managed to listen at -74dB attenuation (the minimum volume Rockbox on my Sansa achieves) when I woke up at 4AM one day, and to my ears, left and right channels were balanced. I blame the ancient Walkman I tested it with earlier for having unbalanced output at low volume, since its volume control is a potentiometer. So if they're balanced, I imagine there is no loss in quality, or you could say that they've equally degraded :D
• The sound of wind blowing against the cord has changed for my closed-design earphones:
the original, thin cord would emit a high pitch whistle. it now gives a middle range howl.
• I don't know what to do in case the paracord gets dirty. It's porous, but at least it won't mold or mildew. Just hope the section to clean isn't around the solderwork. Then again you could seal that with clear nail polish or something?
• It's good to use lengths of paracord that are slightly longer than the corresponding wire sections leading to your ears. I suppose that when they are compressed relative to the wire they sleeve, they will buckle less, therefore making it less likely to form knots when bunched up. These can still tangle, but the knots should be easier to undo than the typical thin rubbery wires they sleeve. As a consequence, however, it may be that compressed paracord will cause it(s fibers) to chafe against itself at the slightest movement, and transfer that sound to your ears. I can't be sure, since I typically use this in a noisy environment anyhow, such as while jogging or mowing the lawn (wearing hearing protection).
• Many months later, I realize that it's better to superglue the ends of the paracord, before shrinking down the heatshrink. I've edited the materials list to reflect this.