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

Mr.  chayro
How old are you?
Cables calculate? If they could also cook we could merry them.

morg111, invective aside, is a truth-teller. The article he cites, http://www.roger-russell.com/wire/wire.htm, is science combined with common sense, and a real money-saver. All that said it makes sense to take care (or pay some company some tens of dollars to take care) with the end connectors to amp and speakers.

Even if could connect our amp to speaker terminals with 1 inch square (cross sectioned), or other rectangular profile, six nines, pure copper bars with only air as the dielectric, there would be NO improvement in sound. None, zilch, zip. Arrrgh!

@ Cquinn-
Sorry, you are right, invective aside, couldn't help it after spending all that time reading this nonsense. But thank you for the backup.

Mr. stevecham
Thanks for reading, but I'm concerned the way you do it...
I wrote that " The electronic point of view, of looking at the electrical current loop of an amplifier, speaker and cables, the speaker cables are an extension of the amplifier ".
Let's say you have an Amp. with a DF of 500. What it means, is that the Amp.'s output resistance is 8 ohms / 500 = 0.016 ohms.
If you add your 8' 12 AWG copper wire, it is equivalent to: 0.0256 ohms.
(it is by the AWG table: https://www.powerstream.com/Wire_Size.htm
- using the feet raw, and do 16' as it is 8' for the red, 8' for the black = 8' *2=16' we end up with this 0.0256 ohms. Your cable have a 1.6 times higher resistance than what your amplifier's DF has. This is like degrading your amplifier's spec. to a DF of only 205. The other 300 were desmissed to a time the speaker cables get better.
You call it  INSIGNIFICANT! (?)
If you would have a tube amp. like the Vtl 250 mono blocks, with an output resistance of 0.86 ohms, you would be right. But with a DF higher than 100, your cable are no Transparent Cables, as Mr. chayro, try to claim. They are far from being perfect. They are most likely holding back your system's performance, by 60% or more.
If you have spent $10k on your system, try to go ack to the genius who sold you this speaker cable, and try to get a refund of $6k, as that kind of money was spent for nothing.
As long as you come up with says that do not rely on some calculations, but only on some bold assumptions based mainly on "Nothing", you can not keep up in this conversation.