I'd like for somebody to explain the reason for speaker wire heavier than 14 gauge copper. That's what I use. I'm not making any judgments but would like scientific proof that heavy speaker wire is better and I'm not saying that heavier wouldn't be better.
Most houses in my area use 14 gauge wire throughout most of the electrical system and would most likely be used anyplace a stereo would be. Most likely you would have more than just an amp/receiver sharing that same circuit. Most people don't run speaker wire very far in their house. I'm not sure what gauge most of my equipment cords are but they sure don't look very heavy. Why would you need heavier wire going out of a amp/receiver than what is coming in. Some of the incoming power is lost to heat or whatever.
I'm not talking about the 1% with the elite systems with dedicated circuits. I'm just talking about the average guy even though that would cover a wide variety and quality of equipment.
I'm not wanting to start a flaming war but just would like some facts.
There's a big electrical difference between the two examples you gave.
Your house mains is running (presumably) Alternating Current (AC). Whereas the signal between your amp and your speakers is Direct Current (DC).
While the need to increase wire gauge to increase the amount of AC Amps pulled through it still exists, it's significantly more forgiving than if it was DC, especially in longer runs. That's why your house wiring can go the distances it does and provide the current it can without the need for it to be very large gauge cable.
DC current, on the other hand, is a lot more difficult to work with in this regard; It does not like to travel long distances. In order to prevent loss of current, as the distance from power source to load gets longer, the gauge of the wires must get smaller (fatter).
It's also the whole reason modern electric grids are AC to begin with. Go back in time to when we first started understanding electricity (Tesla Era), and you'll see that we originally tried to do DC because it's easier to work with (notice that many modern household electrical items have some type of transformer to convert the AC back to DC). But we soon realized that AC was so much easier to supply long distances. To supply comparable DC power those same distances (and I'm talking the miles it travels from power plant to our homes), it would require comically large cables, thus very impractical.
Back to home:
For most home stereos, as you've probably seen stated in your manual and here in your thread, 16 & 14 seem to be the common gauges recommended and used for speakers. But, the manual probably only suggests that size up to a certain distance, and should mention going a size or two bigger if the distance between the amp and the speakers it to be greater. Once again, it's because it's carrying DC current. Like it was mentioned earlier in the thread, it's a common misconception that 'well I've seen the wires in the inside of my amp and they're not big at all, so why should I bother going any bigger when running cables on the outside?' - it all comes back to current and distance.
Those runs inside the amp are a few inches to maybe a foot or so, so there's not much (if any) current loss in there, even in the smaller gauge wire.
But move to the outside of the amp, and you might be running 6, 8, 10, or maybe even 20 feet of cable out to the speakers - (and don't forget, since we're dealing with DC, that's a round trip current run to each, so that distance is technically doubled). So in order to make sure that the full current travels that whole distance with minimal losses, the cable gauge needs to get smaller (fatter), as the distance gets longer.
To visualize this concept a little better, here's a chart I used when I was installing the DC wiring for my solar installation - from the panels, to the controller, to the battery bank, and to the inverter, the same concept applied there too.
I hope this helps make it a little easier to understand.
Now, once you've determined what gauge cable is the most practical for your application, then you get to dive into the wide variety of flavors cables come in - from plain old lamp cord, to supremely finished exotics. And how you determine which, is entirely up to you and your wallet.
Good luck!
