My headphones sometimes don't put out sound in one of the channels, so I opened them up and this question came to mind:
Shouldn't the 3 copper cables that connect to the mini-jack be insulated? One seems to be pure copper, I'm not sure how they changed the color of the other 2 to red and blue but it still looks like bare copper to my eyes.
They are insulated. Each individual strand is coated in blue, red (is it red?) or clear enamel.
It makes soldering it a bit of a pain, but makes for very flexible wires, and also reduces the high frequency impedance of the wire by massively increasing the surface area of each wire.
It is called "Litz Wire", and the reasoning behind it is to reduce the Skin Effect which causes increased resistances in AC waveforms.
The wire looks like enameled wire to me, basically copper wire coated with a very thin insulating material.
It probably isn't Litz wire.
The secret of Litz is the way the insulated strands are woven. Like rope, the strands are twisted into bundles, then the individual bundles are themselves twisted. This means that each strand spends an equal time at all layers in the cable. It is done to reduce proximity effect with adjacent bundles at Radio Frequencies.
This is of course expensive and requires special machinery. At audio frequencies there is no advantage, so headphone wires are just multiple parallel strands.
