@thecarpathian
You asked in my opinion what "is the best type copper for cable application?".
I am here primarily to learn, so really I am the worst person to ask! However my physics background forces me to apply Occam's razor to claims. If there is a simple explanation, it is more likely to be correct than a complex one. Or as Einstein said, make the explanation as simple as possible, but not more so.
To your question: Theoretically, for high voltage transmissions lines, aluminium is best with a steel core to hold it up.
For microwave frequencies, use hollow pipes because of the skin effect.
For speakers, usually a high current application, the shorter the better. Ideally the amplifier is in the speaker so its output can be feedback-corrected to match the speaker. Otherwise you probably want low resistance in the cable and the connectors. If you halve the length, or double the cross section, you halve the resistance. Note that all speakers have varying impedance across their frequency range, especially around cross-over regions. Changing the resistance of the cable will alter the tonal balance, for better or worse. Changing the purity and crystal structure only have small effects on resistance.
The mere act of changing a cable scrapes oxidation from its connector surfaces, and suddenly the resistance drops a bit. The speaker gets a bit louder and louder sounds better.
In practice, most of my cables are cheap! I did buy one slightly up market power cord but I cannot find it. I did modify one power cord by adding ferrite chokes to mitigate RFI emissions and that solved a particular problem. I still feed my Quad electrostatics with the Naim speaker wire my dealer threw in forty years ago. I re-terminate it every few years.
When I bought current-hungry KEF Reference 1 speakers I bought a pair of QED silver coated copper leads with a fancy twist, secondhand. I could bi-wire them but can't be bothered - still enjoying them too much.
I did buy some van den Hul balanced interconnects, because the blurb on their website made some sense from a physics viewpoint. They use the cable weave invented by Alexander Graham Bell.
Am still seeking advice on rewiring my old SME tonearm! Reducing the number of corroded connections and going balanced has some appeal! Siver litz or copper?
My digital connections are all HDMI, no dramas as long as they include Ethernet. I only stream audio in order to sample tracks, and then it is WiFi to my phone and Bluetooth to my pre-amplifier.
Basically a cable sceptic but so many report benefits, they can't all be wrong. Can they?
