yes, shielding is a must when considering wire for SIGNAL lines.
the reasoning is - you are sending milivolts down these lines, not something like 20~30acv that has a strong signal out of the amp - and needs no signal reinforcement.
since there are many many emi producing things inside a car, for example, the alternator is one of the MAIN emi producing devices there is, and the power wire run from your battery to your amps.
every current of electricity produces its own little electromagnetic field. this is the basis of how a speaker works. by coiling the wire upon itself, you generate a compound field that can get quite strong. so strong in fact, they are making a class-21 carrier for the US navy that uses electro magnets to launch the multi-ton jets from 0 to 200+ mph in a few seconds. so a power wires magnetic field is so much stronger than the field from the singal of your music (wich for most headunits, the max output is 2v and almost no current) that it will introduce noise by radiation into the signal - usually a high pitched whine caused by the alternators revolutions and feedback into the electrical system of the car.
so. in short. a (or multiple) braided shield is used in conjunction with dielectric materials to repel outward electromagnetic interference and keep the origional field integrity.
thus - me looking for cost effective and pretty RCA signal wire so i can build my cables to the length of my vehicle while keeping induced noise at a minimum. and i think im going to look into the Canare star quad wire because it looks like the exact thing im needing //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
thanks otrhorse. that was exactally what i was looking for.