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

Sorry, pal, but your numbers are off by about 3 orders of magnitude. Nobody is using 200mm long speaker cables. More like 2000mm. That puts the final equation out around .25 ohm. 

Why do you think some people use Litz wire for interconnects? It's because the inductance of solid wire presents audiblo significant impedance to high frequencies. That's why I can't use Litz wire with my amp. It doesn't present the impedance required to damp the oscillation that can result from a bad ground, and with 1MHz full power bandwidth, it WILL amplify all kinds of things. If your misinterpretation were correct, it wouldn't make any difference. 

Sorry for the "0" on length. The new value is 0.00369 ohms and not 0.25 ohms as you say. Anyway, what about my Q:
"From where do you take this information about cable thickness and massive amount of impedance?"

Regarding Interconnects, it's another thread...

I use XLR, no Litz. The entire Pro industry use XLR, at length of 100 meters and longer, no loss! On 2m, it is perfect.

Are you using 0g XLR cables? NO. Are CAT6 ethernet cables built from 8g? NO. Are USB cables as big as my arm? NO. You’re proving my point, not refuting it! You can jam crazy high alternating voltages down a thin conductor with negligible impedance, and it’s generally preferable to do so. That’s why utility companies do it. 

As for your calculator... Learn how to read it. You’re looking at the wrong value. You’re quoting the skin depth impedance, not the full diameter impedance. It’s pretty freaking obvious. That’s why the number you quote is such a small figure and hardly changes with length.

Read this: https://www.passdiy.com/project/articles/speaker-cables

Nelson Pass did the measurements and they’re not even close to the stuff you’re saying. I’m going to trust his actual measurements a little bit more than your misinterpreted internet calculator speculation.

A short reminder: This thread is about speakers cables. 

No LAN cat 6, No balanced interconnects (XLR) or any other.

Until you answer my Q. don't expect to be answered.

With all the respect to Mr. Nelson Pass he went the wrong path. No one here approved his cable sounds better than other, but mine did.  

"With all the respect to Mr. Nelson Pass he went the wrong path."
- Now that's rich, have you any idea what he has accomplished?

"No one here approved his cable sounds better than other, but mine did."
- Nelson Pass doesn't make cables. You have stated 6 people have tried your "secret formula", only the ones that have shared their results on this thread have standing. The others are hearsay. Why don't you reveal your formula?
Educate yourself: https://www.passlabs.com/#