So you think wire conductors in cables are directional? Think again...

In all seriousness, to the OP: who cares. 
Step One: cables arrive

Step two: if they have arrows, place them according to arrows

Step three: done

Why is this so tough??

Unless of course you buy stupid shit Christmas “wire” from Home Depot, and are wondering why they don’t have any arrows on them. 
Which begs the question: why do YOU even have to worry about the directionally of the cable?

If wire had directionality to audio signals somebody would already have invented a device to measure and quantify it! So where's this device? 

Engineering wise, conductor signal direction makes no sense, especially since we are talking about AC signals that change directions anyway.


Doesn't the electromagnetic wave propagate away from the source?

All we get so far are the wise sages listening to their wires and acting like the four blind men and an elephant!