Originally Posted by sivadselim
It IS a weakest link scenario. If the external wiring doesn't transmit the signal properly in the first place, then it is the weakest link.
Reading your whole post, I do believe that you understand what your talking about Siv, so I'm not really going to disagree with you. However, the way your saying it may be somewhat misleading to those who don't understand, so I'm going to help clarify.
The resistance is indeed additive, as was explained by xradman. You cannot argue with mathmatics in that case. It is not the same thing as water flowing through a pipe, although some analogies can be drawn (explained below). We are talking about electrical signals not physical mass, they behave differently. Water flowing through a pipe experiences an increase in pressure drop when forced into a smaller pipe at higher velocity, the only way to keep the overall mass flow the same (given a constant desired end pressure). You can, however, add up the pressure drop from different length and diameter sections of a pipe to determine the overall pressure drop of a pipe run, which could be considered similar to the speaker analogy, in a way. Then, depending on the end pressure desired, you can calculate what the initial pressure needs to be to force the flow through the pipe (in a way, similar to the required amount of current needed for a speaker wire run, for desired volume). If you have enough headroom on your amplifier, this isn't really of much concern, just like if you had plenty of pressure to spare for the water flow.
I believe, however, what Siv was getting at was potential interference of the electrical signal from outside sources due to poor insulation of the wire. Higher guage (thinner) wire typically is less shielded, making it more susceptable to interference. If the original run provides a distorted signal to the inside of the speaker, it doesn't matter what the inside of the speaker is capable of. Likewise, if the inside of the speaker run creates an interference in the signal, it won't really matter what type of wire you've run outside the speaker. My personal opinion would be that reputable speakers will have an internal wire run that will not provide any meaningful problems in this regard. I just can't see how they'd spend so much money designing speakers that cost a thousand or more and limit themselves with a $2 problem that could be easily solved.
So, the difference in the water-pipe analogy and speaker wire is that water cannot escape from, nor can any water be introduce into the pipe, as a variable of the size of the pipe. That isn't necessarily the case with the electrical signal being transmitted through speaker wire.