What wire runs between two speakers on a headphone, and how do I replace it?

Question

I have a Sennheiser HD 280 Pro pair of headphones. There is a wire running through the bow that connects the left speaker in the headphone to the right one (see drawing, red line), I managed to snap this wire.

The wire looks like it has some sort of red-colored core, copper wires wrapped around that core, and a fluffy insulator.

I have taken some pictures of what that looks like:

left side:

right side:

What type of wire is this, and what would be my best bet at repairing it?

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Update: Currently trying to obtain the wire. Have tried two separate wires, but there is very little space inside the headphone. In this forum post they say the gauge of the wire that's in the headphone is 15 gauge total, with the internal wires being 27 gauge each.

Answer 1

The short answer is you can use pretty much any thin two core stranded wire. The fluffy stuff is just cheapness; manufacturers have been experimenting for years as to how much copper they can replace with bits of string to save cost; it offers some strength but is cheaper than metal. It's not an insulator, just a mechanical component.

If you want to joint onto the ends of the current wire, the tricky part will be finding enough copper to solder to. This wire is coaxial so you'd want to solder one of your new cores to the centre core, heatshrink over that, then solder the outer braid (what there is of it) with some more heatshrink over the whole lot. You'll likely though be able to find better connection options within the muffs themselves.

Answer 2

Okay I finally managed to get it fixed (ish). Please keep in mind, I know very little of what I am doing, so I wouldn't suggest using this as a guide per se. Like Ian said, any two core wire will do. Based on this post, I found the wire thickness to be 15 gauge total, with the internal wires being 27 gauge each. I couldn't find a dual core wire with the same thickness so ended up buying these, 30 awg wires (I would advice buying two colors to keep track of +/-). IMPORTANTLY, after the fix, the speakers are working great, but I can't adjust the headband any longer. This has to do with the fact I bought two separate wires, and they dislodge themselves in the headphone, getting stuck in the adjustment mechanism. Additionally I have, sometimes, some interference in the headphone (sounds like the noise speakers used to make when getting a text).

Opening the headphones is pretty straight forward, everything is held in place by small torx like screws. Do take pictures of everything along the way to make sure how it was assembled, especially the electronics. I used this guide as a reference for taking apart (do note, if you just want to replace the wire between the speakers, you don't have to follow every step in the guide).

Important things to take pictures of:

Controller board slot in one of the earpieces:

and the wiring on that same board:

direction of wiring on the two speakers:

I first ran the new wires through the back of the headphone, everything should come apart, so you have easy access the replace the broken wire:

This is where my wires kept dislodging and getting stuck in the adjustment mechanism:

I then resoldered the new wires to the speakers, and the small controller board in the same +/- order as they were in. Reassembled the headphone and tested it.

Overall the headphones have been working great for the past 2 ish weeks with almost entire day usage. The only two problems with this fix are the lack of adjustment after re-assembly and the occasional (maybe once every two days for a couple seconds) interference.

Hope this can help anyone else, and do let me know if you have any questions.