My speakers were made in 1989 using the old Kimber Kable teflon coated wire internally. Hopefully, since all the connections are soldered, there's no oxidation going on.
Years ago I ran the Kimber Kable braded strands as speaker cables, but they were too short for my current room when we moved in 1999 to a larger home. Thanks to the internet, I kept reading that speaker wires don't make an audible difference, which had contradicted my previous beliefs, but since money was tight I bought some inexpensive 16 gauge CCA wire.....it didn't sound nearly as good, but I attributed it to the sound of the new room. My beloved system sounded uninviting and uninspiring, and I lost some interest.
Years later I upgraded with some decent 4 conductor OFC wire that sounded so much nicer. I stopped listening to the cable deniers right then there, and have gone my own way ever since. Wire, cables, connectors, caps, amps, opamps, power supplies, DACs, tubes, isolation, etc, can not only make an audible difference, but they're cumulative! The weakest link theory applies....I try to leave no stone unturned, and I'm extremely happy with my system these days. Even if it's all in my head, it's noticeable every time I listen, so I don't really care what the cause is.