Dorten, the answer to your last question is: "Yes."

Just as in power wiring, the wire size (gauge) is determined by the desire to lose as little power as possible in the conductor, so maximum power is delivered to the load. The power not delivered to the load heats the conductor due to IR2 (current x resistance squared) losses, also known as voltage drop.

However, as with most things, there is a point beyond which the additional gain (actually, less loss) is no longer worth the additional cost. This is known as diminishing returns.

The length of the conductors (round trip distance) is one component used to determine the conductor size. The electrical current of the load is another. The longer the run, and/or the higher the power desired is another.

General consensus is that, because the distance to the rears is (usually) greater than the fronts, but the loudness of the fronts is (usually) greater, you may as well settle on the same size wire for all channels.

But, what size? For typical smaller rooms, with less than 100W/channel, an 18 ga. or 16 ga. wire should be sufficient. Anything larger and/or more powerful, I'd go to 14 ga. or 12 ga. (Note: higher gauge number refers to a smaller conductor)

My system, for example, has the mains (L & R front) powered by a stereo amp rated at 300W/ch., and the center, sides, and rears powered by a 5-channel amp rated at 200W/ch. My amps are below my center speaker, with about 3 ft. of wire to the center, about 6 ft. to the mains, and about 24 ft. to the sides and rears.

I use a high-quality "ordinary" rope-layed (limp) speaker wire of 12 ga. all around. I consider that size a satisfactory compromise between pereformance and cost. I guess the answer to your first question would be: "Not really."

Larry
www.fineelectricco.com