Copper foil

For speaker cables, try 5mil x 2", or 7mil x 2" for more LF emphasis.

The ends can be folded down to a pointed triangle and shaped with needle-nose pliers for crimping & soldering inside a convention spade. Alternatively the ends can be folded into several thicknesses and punched for direct copper termination. A Cardas no-stress binding post is perfect for this, as it clamps down without twisting.

Palerider, Far from "hi-fi legend," skin effect at AC is well documented as variation in impedance against frequency that occurs at difference depths of a conductor. The effect becomes pronounced at frequencies above a few kHz. It's not true that signal travels only on the surface of the conductor, but it is true that the larger a conductor's diameter, the more skin effect causes audible frequency shift. This is why litz wiring was conceived.

Ribbons sound great because of reduced skin effect. However you are correct that adequate conductor guage is also significant. The 2"x .005" copper ribbons I'm using as speaker cables have a cross-sectional area of 6.45 mm2-- about the same as a 9awg round wire.

Rather than explore relevant Bessel functions & Maxwell equations in a non-technical forum, I suggest that doubters spend $100 at McMaster-Carr for some electronics-grade copper of equivalent gauges in both formats & experiment. You will be surprised.

Nordost, Goertz, Mapleshade, Allen Wright/VSE are a few. McMaster-Carr sells raw electronics-grade copper and there are several small distributors of silver foil.