No one actually knows how to lculate what speaker cable they need

b4icu,

Thanks for all of this. I completely forgot about the weight which may become an issue. I guess, I could try with a little thinner cable that would be easier fit. It just seems like some easy game that is not that hard to do and costs quite close to a dinner for two around here. I think that it my case it would be sonically completely unimportant, but why not try. If my cables were any shorter, my speakers would be called headphones.

I am sure you have noticed the difference in attitude that other posters have towards your original post and ideas after you have started explaining your thoughts and giving practical examples. Now, if everyone tried to do what you suggest, we may get an answer if you are correct in your convictions about cable manufacturers. Luckily, there are other threads that deal with that.

A 4/0 AWG or 0000 AWG has a cross section of "only" 2x a 0 AWG as well as better resistance.
By the AWG table, the steps between two consecutive AWG cables is not twice as good resistance.
When I write 2x 0 AWG, I meant two 0 AWG cables in parallel.
When I write 4x 0 AWG, I meant four 0 AWG cables in parallel.
If you could use two mono blocks, placed next to the speakers, or back to back, it would be way thinner.

When someone have a fireplace between the speakers and requires 20'+ to make the distance between the amp. and the speakers,

It takes the extra thickness, to compensate for the length.

The cable resistance formula: R = ρ x L/S when ρ is the cooper conductivity (1.68x10-8), L is the length in meters and S is the cross section in square mm.

If length gets twice longer, so needs the cross section, to keep the same resistance:  R