Dumb Question about cables

That's not a dumb question at all, in fact it makes a lot of sense to wonder about that. I don't know what the answer is, but have wondered about it the same as you.

can't wait to hear the reason. i only know purple cables sound better than red ones, which in turn sound better then black ones.

Cables act like antennas. The longer the antenna (Cable), the better they pick up signals. If you have an 8 foot unshielded cable, you in effect have an 8 foot antenna. By applying insulation, you reduce the effective length of the antenna i.e. cable from picking up EMI and RFI. You can never eliminate the effects of the cable from picking up EMI and RFI, but the application of insulation will reduce the effects substantially.

Insulation (usually plastic) is for keeping electrical shorts from happening. It does not primarily serve as a shield from EMI and RFI (both of which are just terms for the same thing because radio waves are electromagnetic waves). Insulation does not shield. A shield shields. A shield is made out of a conductive material. An insulation is made out of a non-conducting material.

If you are referring to speaker cables, where the cable is huge and the endings are thinner, this is mainly just for flexibility and ease of use. It is a "necessary" compromise because you have to hook up the cable somehow, and each speaker manufacturer has different widths between their input terminals.

Louis Motek