Cables (interconnects, speaker cables, power cables...etc.) are generally made up of a number of very small diameter "wires". These small diameter wires are made by "drawing" a single large diameter wire through progressivly smaller diameter "dies" until the desired diameter wire is achieved. The process of drawing a wire through dies generally involves pulling (under great force) the wire through the dies making it smaller (and longer) as it goes through the dies. As the wire goes through the dies the molecular structure of the wire is changed. The molecular structure will take on a "directional" structure that represents the direction that the wire has been pulled through the dies. This directional molecular structure can produce different electrical characteristics in one direction than in the opposite direction. Measurement of these electrical characteristics requires extremly accurate electrical diagnostic equipment (you ain't gonna see it on a rat shak digital multimeter).
Based on this we can draw some conslusions.
1. Some cable manfacturers simply buy good wire, have it coated with an insulator amd make cables.
2. Some cable manfacturers have very sensitive test equipment that allows them to buy good wire have it coated with an insulator and perform tests for resistance in both directions. Upon determining the direction of least resistance they mark it as directional, terminate it, package it and sell it.
3. Some cable manfacturers simply require (specify) that their wire manfacturer indicate the direction of draw, coat with an insulator terminate, package and sell.
4. Other cable manfacturers have the necessary analytical equipment and require their wire suppliers to indicate the direction of draw and perhaps even specify the amount of cross-sectional reduction per die, maximum and minimum draw temperature as well as direction of spooling, spooling tension. spooling temperature........on and on.
Think about all of the possibilities. Are cables directional......? You tell me. My test equipment will not tell me that they are or are not. My technical education and job experience tell me that cables are directional. Thoughts....Ideas.....Rebuttals.....? Thanks :-) Doug