Let's be clear. I am NOT saying there is no difference above the "bad" level. I am not telling you if you hear something or not. I am not saying the simplistic measurements sometimes quoted are the whole story. I do want to be clear we can measure all parameters of a cable. We just don't know how to quantify them as a minimum " good enough" combination for one person, let alone everyone's personal preferences.
No, I believe what I hear. I know it may be real or may be in my head. I believe in the laws of physics so those things I know are impossible, I know are impossible. Being an engineer, I know how these things work to a reasonable scale so I know when the invented logic of snake oil salesmen or well meaning people making false logical jumps without the technical understanding come up with pure BS. BS is actually very good. Makes clay soils much better. Not my stereo though.
I also know from soft science, we do not understand very well how our brain converts reality to what we hear. We have some clues. Small linear distortions and small timing differences we seem to detect. We seem to detect timing differences across frequencies our brain does not recognize as natural. We also know our brain "maps" our environment and makes adjustments over time. If anyone can point to some papers quantifying these issues, I would love to read it. Better yet, if you are a grad student looking for a project, there is a lot to be learned.
We know a preconceived negative expectation can create a difference in our head even though no actual difference exists. We know a positive bias will also generate a positive response. We know our brain likes to play tricks on us and flip what we hear from reality. We know these biases may not hear a difference even when there is one large enough that we should. Everything we do is biased. If you ask a random person if they hear a difference, we know a large portion will hear a difference even if there is not one because we biased them with the expectation of a difference. This has been demonstrated many times to statistically valid levels. We know group think and reinforcement will strongly bias our perception. This is why witness evidence is recognized as the least reliable in court.
So, by understanding both hard and soft science, I can take a much shorter route to better sound and avoid the clear snake oil ethereal made up attribute magic crap. I can make a reasonable guess where to stop as we leave engineering into magic.
Follow the old 90% rule. Find your biggest problem and fix 90% of it. Then find your next biggest and fix 90% of that. That last 10% may or may not even be achievable and you get lost in a rabbit hole without improving the situation as a whole. In theory, that first last 10% will become the largest remaining problem, and you then attack it. In reality, it never happens. Not only are the very best speakers still pretty poor, the source material is even worse. In other words, don't expect a cable to fix either.
Today we have an advantage we did not have way back in the 70's. We have instrumentation thousands of times better. We can do things like hook a cable up and measure the signal at both ends, subtracting one from another to quantify the difference. Qualifying it is harder. There is no longer a reason to use pure subjective imagination to look for differences. Alas, the SINAD chasers are stuck in a very limited set of measurements and the subjectivists are completely controlled by their unconscious bias. I hope real engineers keep an open mind and if a statically valid subjective test shows a difference, we should look to measure and quantify it. Quite a mess. If the esoteric hucksters could prove their cable is better, they have the money to do so. Not even publishing the R-L-C parameters and explain why their balance is better. No data on rejection vs frequency. ( go look at a Belden data sheet. You find a lot more parameters! ) Some on geometry and engineers can make an educated guess why one many be better at some particular issue than another. Things any engineer wants to know when selecting a cable. Nope, hucksters just make up slick-page hyperbole and tell you how great it all is. A lot of exotic products are perfectly fine. Just not magical. Some people still believe the world if flat and we did not land on the moon. That is religion and is not easily swayed.
So in the middle. I use my understanding of physics to rule out the total BS. I can look at measurements on some things to rule out the obvious crap. Then I have to listen. 100% accurate? Heck no, but neither are any of the supposed double blind tests I have read as none of them reach the 3 sigma level to pay attention to, let alone 5. I have won 20 games of solitaire in a row. Taken as a sample, I am so great I win 100% of the time! No it means I still only average 40% over sets of 100. A statistical anomaly is all. A lot of reviewers need to study statistics before them make claims on tests.
Now, the really hard part. Do you want your cable to be part of the signal shaping distortion adding part of reproduction, or do you want it to just convey the signal? BOTH are valid. Same argument of SS vs tubes. I happen to prefer my MOSFET amp to a Benchmark. Is it some added distortion I like, some higher distortion masking something I do not? Some more complex distortion not typically measured? Not a clue but I know what I prefer and there are real measurable parameters that could explain the differences. I just don't know which ones.
Or do you want to let your belief that nirvana is just within reach with one more tweak? Subconsciously, if it costs more it has to be better? Music is all in your mind, so how you get there is up to you. I am not filthy rich, so I take the shorter path that falls within the expectations of reality. My budget is to save for a new roof before it is needed, not a set of speaker cables.
FEDX should deliver my new amp today. I have an appointment with a parlor next week to see if I can hear a meaningful difference between my DAC and a Chord or the other mega-buck ones he has. I go in with a bias. Half says my DACs have reached the as good-as-I-can-hear and the specs are better than the Mojo or Qurest, the other half of my bias is there is still some "digititus" to be smoothed by a more expensive product. Should be fun.