Lacee - don't forget that the differences they may fail to detect also depends on the other cables in their systems which may or may not allow them to hear a difference.
If either the speaker cables or interconnects are not of sufficient quality or gauge, they will not hear any improvement.
I have very good 10 gauge speaker cables and phono interconnects with balanced conductors and directional screens. They make a huge difference to the complete sound and allowed me to hear improvements
But you are correct in that people listen for different things - e.g. I listen to the musical phrasing, not the actual words.
If either the speaker cables or interconnects are not of sufficient quality or gauge, they will not hear any improvement.
I have very good 10 gauge speaker cables and phono interconnects with balanced conductors and directional screens. They make a huge difference to the complete sound and allowed me to hear improvements
But you are correct in that people listen for different things - e.g. I listen to the musical phrasing, not the actual words.