A superior speaker cable must minimize all impedance elements – resistance, inductance, and capacitance. Each of these will result in a speaker terminal voltage that is different than what your amplifier is producing. That’s a loose definition of ‘signal loss.’

Each of the three impedance elements are functions of material, geometry, and frequency. To reduce resistance (for a given material and conductor length), the cross-sectional area must be increased. Unfortunately, for solid or multi-stranded conductors, as frequency increases, the effective cross-sectional area becomes a smaller fraction of the actual area. You can thank magnetic fields for this, as these force the current to flow only within a fraction of the total conductor area. As frequency increases, this effect is more pronounced.

This resistance increase comes in two flavors — 1) proximity losses and 2) skin effect losses. Proximity losses are due to the magnetic fields created by currents in adjacent filaments, and skin effect losses are due to the currents’ self-created fields. These effects limit the possible reduction of resistance at high frequencies regardless of the size of the conductor.   

Litz conductors do a great job of reducing skin effect losses. A litz conductor is not only multi-stranded, but each strand is insulated. With a small enough strand diameter, the skin effect losses are effectively eliminated. However, proximity losses will begin to increase at some frequency, depending on the bundle size and braiding geometry. Minimizing both effects without consequences is a complex design problem, and basic electrical models aren’t sufficient to help in the design process.

As with all designs, the number one rule of engineering applies — there ain’t no free lunch. Optimizing one aspect of a cable will result in some penalty. A theoretically zero-inductance cable would have infinite capacitance and zero signal transfer. A cable with ‘negligible’ capacitance would have excessive inductance and resistance.

Good cable designs are also highly dependent on the frequencies involved — you can’t use coax for speaker cables or AWG#2 for RF antennas, even though the same fundamentals apply.

Getting a cable design right to handle a reasonable frequency range (for audio, at least 3 decades or a factor of 1000) is easy for the first 80% and very challenging for the last 5%. The toolbox must include testing techniques and equipment to isolate the impedance elements during the design process. Using a half-analytical, half-empirical design approach, the cable’s impact on the system can be reduced to a level that is not truly zero (this is impossible), but effectively inaudible.

-SMR