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

Not sure I go along with the presumption that Kimber 12TC are “high end cables.” I guess we need to define what high end cables means.  Kimber does have good name recognition going for him, however. I’ll give him that. By the way sales of fake Kimber 12TC cables appears to be rather brisk on eBay. Maybe I’m missing something.

On another subject I’m not sure why people assume that a given set of components have a certain predictable level of sound quality or that photos of a system reveal anything about how it sounds. There are way too many variables to be able to make such judgements.

Kimber 12TC Electrical Specifications:

(Cp) parallel capacitance: 494 pF / meter - (Ls) series inductance: 0.09 uH / meter - (Rdc) dc loop resistance: 0.005 Ohm / meter.

geoff is correct, here is an ad for fake Kimber 12TC

https://www.ebay.com/itm/1pair-FOR-Kimber-12TC-8N-OCC-Main-Speaker-cable-Rhodium-plated-Y-plug-1-5M-...

https://www.kimber.com/counterfeits

Neither of those responses really answer my question, other than: we don’t know how it’ll sound.

quite the punt then at $1000 from here: https://www.russandrews.com/kimber-12tc-speaker-cable-biwire-kimber-bananas-31909999101/

I’m not trying to be cryptic or trap anyone. An important factor in any good experiment design is to determine what success looks like.

I’ve done everything I think I can: dedicated power circuits, decent components, good sources, good speakers, room analysis, there’s really not much more I can do. I’m trying to put myself in the best position to determine if I can hear a difference between speaker cables. If I can, great, if I can’t, then they’re going back. They might go back anyway if they don’t make enough of a difference. And no, I don’t know what “enough” is for me to feel like I’m getting good value.

anyway. I’ll report back when I’ve tried them out.

Folks, everyone is talking resistance but there are two other factors that come into play.   One is the inductance and capacitance of the cable, the other is the skin effect.   For audio work, skin effect becomes a non issue when the wire is 16 g copper or thicker, and I doubt anyone reading this is using 20 or 18 g wire.  The other is capacitance and inductance and these are tied together.  If you are using dynamic loudspeakers, that is a speaker whose motor is a magnet with a voice coil and cone, then one needs very low inductance cable with the result of it being higher capacitance.  The reason is inductance becomes a significant factor when the load impedance is low and most speakers have impedance dips below 8 Ohms and peaks above 8 Ohms.   This causes an attenuation of signal if the cable is not low inductance.   Plain zip cord is fairly inductive and thicker zip cord, that is the stuff with larger gauge copper, becomes even more inductive while the resistance drops.   This is the reason speaker cables sound different.   If you have a non dynamic speaker, that is a pure resistance load, i.e. Magnapan, ribbons, etc. or an electrostatic, then the parameters change.   Resistive speakers require low resistance and a moderate inductance cable while electrostatic speakers are a special case but can more or less live with higher inductance cables.  There are other losses as well, but these variables are secondary to the above.
Regarding the question why no manufacturer will calculate the cable needed is a lot depends on the output impedance and phase margin of the amplifier.   One just can't hang high capacitance on the output of an amp, it might cause it to oscillate. At the very least, it won't like the load; worst case is the amplifier dies a violent death.  No cable manufacturer is going to take that risk, rather it is left up to the user to sort all this out.