Directionality Explained

If the impact on frequency response is <0.1db there is little(no) evidence we can detect a difference and even more variance at the upper end of the spectrum to detect a difference. Now try to find a cable not inherently directional, i.e. with circuitry that has 0.1db difference in the audio spectrum by changing direction. Feel free to use square waves for tests with bandwidth limiting and real speakers for transmission line effects.

I don’t think it’s just one number. Anyway, I think our audible perception of music is a bit more complicated than just one or two simple measurements.

Also why ".1dB"? Somebody would come here and say "no, it’s more like 0.08dB". It seems a bit arbitrary.  And it comes back to what has been said "who gets to decide?".

Also you may have a situation in which you have a set of cables all will meet your "0.1dB" threshold, but they all will sound different for obvious reason.

I believe that there are aspects of hearing that machines do not measure.

I think human hearing is just to complicated to be analyzed by just one or two numbers.  

Instruments cannot capture the entire event in any way approaching how we hear. They can only capture a pre determined aspect of a sound. 

Quote-"I believe that there are aspects of hearing that machines do not measure"
.
At the current time I am sure that we are not even asking the "correct" questions. And without those questions how do you measure? What do you measure? What scale is to be used?
Do we really ever use simply "one’, sense at a time? What about that pesky, "Sixth" sense?
How much of a role does "individual perception", play? 
Simply one’s mood can change any "perception". Hence how does that variable factor? 
And in how many ways? New scale?
On and on and on.
Let alone the design of any apparatus to help us measure, "quantify", in any meaningful way or even just to "qualify" in any way at all? Any result?
It Is therefore currently beyond our capabilities. But that shall not be true forever. It could be a relatively long wait though, "In case you happen to be in a hurried state".
Yet,
At least we are having this discussion. Which would never have taken place even a few decades before now. And "This", IS indeed part of the process!
No less important than any other part. "And quite possibly more important than many others".
Therefore;
Congratulations!

Your "involvement", in this thread, has moved "Human Understanding" forward.
By approximately "one", (standard), "iota"!
Shall we go for two?