Why are headphone cables shielded?

[jaencer]

I don't see the reason why pretty much ALL commercial headphones come with shielded wires (even the economy HPs). I mean, how much EMI or RFI noise would actually be audible? If you took an unshielded headphone cable and put it right next to a transformer, it still probably would move the diaphram enough to be audible...
Speaker cables aren't normall shielded, and headphones are little speakers...
So why are headphone cables shielded? Is it to reduce noise injected back into the circuit (and why would that be a problem? what would that do?)

Thanks for your knowlege

 

[Iain McNeill]

My guess is because shielded 2 conductor cable terminated on a stereo 3.5mm plug is mass produced in China for pennies. The shield does nothing as you say because of the low impedance of the amplifier and transducers.

It may also offer some strength to prevent the thin wires from breaking, but my money is on the cost factor.

 

[Jen-B]

Iain you are right that it's cheap in quantity, but it would be even cheaper if it was not there. I think the actual answer is that it's a combination of additional strength and crush protection.

 

[mjf]

hello.
i have a headphone connected to my computer soundcard.
with the shielded lengthening cable all is quiet,but with the unshielded cable i can hear a little (modem)noise in the background..........
greets

 

[qusp]

headphone cables are inherently low power/high sensitivity devices, which are much more susceptible to noise than wires carrying high current. a few microvolts of noise coupled into a headphone cable has a MUCH larger effect on the drivers as a result. that being said I only ever use shielding on home headphone cables (single ended) as they are generally much longer and tend to pass by more sources of interference than the occasional mobile phone tower like with portable. the home is literally full of noise these days with wireless LANs etc.

hope that answers your question