Directional speaker wires, what and why.

I've been aware for a long time that some speaker cables are designated as "directional". To a limited extent I can understand the rational behind choices based on wire size and construction, biwiring, etc. but don't understand how any conductor can have directional characteristics even in a DC circuit. I'm not denying the possibility but can someone please clarify this for me?

The only reason this comes up is that some time ago, I changed from spades to locking bananas on my wires. It was just yesterday that I noticed that my cables have arrows printed on them indicating, I suppose, that they should be hooked up with the arrows pointing toward the speakers from the amp. The cables in question, btw, are Straightwire Octave 2's.

I've experimented with speaker wires in an attempt to optimize my system but have never been able to discern much, if any, difference between them. That being the case, though, I now don't know whether these have been situated incorrectly since about 2004 when I bought them with my Martin Logan Odyssey speakers.

How can there be a directional character to a conductor and how does that affect sound?