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


It goes back to cable manufaturars, mostly provide no relevant data! to sales and the users. None will answer this!
Whay do you think that you own now the optimal cable to your setup?
I think I've figured it out. 


128x128b4icu
Post removed 
8 Ohm nominal speaker impedance +
0.0256 Ohm cable resistance =
8.0256 total nominal amp load.

Amp output impedance 0.016 Ohms
DF (which is a ratio, not units) into 8 Ohms is 8/0.016 = 500
DF into 8.0256 Ohms is 8.0256/0.016 = 501.6

Big difference. Not.
Hi there . For me every thing is simple. Top line speakers as well as amp ,power amp, preamp, cables and ofcours most expensive on entire world . And no question, no more arguments . It must sound good. I might invent something exceptional something extremely good sounding, but who is going to admire it , I got no name. We already have a gurus who are on the top. I should maybe write, money talks as simple. Thank you , nothing to argue about.
Poor wording on my part.  No the cables do not calculate.  The company measures all of your components' parameters and the company builds a cable with a network that that takes all of those factors into account.  Now your search is over.  Sorry for the ambiguity.  
Mr. stevecham

The speaker's 8 ohms is not a part of this calculation.


Your first par. adds the speaker impedance with the cable resistance (like adding bananas with apples!). The concept is wrong.
The speaker's cables resistance is not part of the load (speakers). They are an extension of the amplifier, just as I claimed before.

Your second par. is also wrong! DF is always related to 8 ohms (@1kHz), even if the actual speaker to connected is other (4 ohms or higher than 8 ohms). It is a fix number = 8.

In overall, your way doesn't fit the actual relations, nor explain what different cables sound different. As if you would be right, all cables would sound the same.