Correct, am still investigating this but here is what I found from a Sound Stage interview of Lars Risbo of Purifi…
Purifies reliance on speakONs intrigued me, so I asked them about it. Lars Risbo:
Nearly all binding posts and/or banana plugs available we found to be magnetic and added measurable hysteric distortion. The cheapest plastic speakON passed the test. It seems that Benchmark Media Systems came to the same conclusion with their very low distortion AHB2 amplifier.
I have quoted some of your post for that very reason. Being Technically correct, reliable and also in my experience objectively presented without coloration from personal bias.
And yes, the steel thing is a non issue, obviously at the other end of the speaker cables connected to that Buckeye amp there is going to be a loudspeaker driver of some sort. The material in the terminals of that driver is not going to be even remotely relevant for the performance of said driver because it has so many other shortcomings that dwarfs whatever little impact the terminal material could have
But it is easy to forget sometimes that whatever the equipment and regardless of how good they measure, the real bottle neck are the speakers, and for the most part they are not going to be anywhere near as revealing as an AP analyzer