BTW I went from Hale School to The University of Western Australia where I completed a five-year Communications Engineering degree course, 1961 - 1965.
The first impedance matched cables came from Japan and were invented by Shin Endo, UK patent attached and were marketed by Monitor Audio in the UK and by Polk in the USA. We used the cables exclusively as they sounded better than all other cables and they worked perfectly with competently designed amplifiers.
Unfortunately, they blew up the conditionally stable Naim amplifiers and a few others. However, Naim were so powerful, they forced the Monitor audio cable off the market.
Now that there was no off-the-shelf impedance-matched cable, we made our own by paralleling up six 50ohm coaxial cables to get 8.2ohms in about 1983. It worked as well as the Shin. Joining the 900 odd strands of copper when paralleling RG213/U required lots of soldering, hence I solder and I solder, became Isolda. Unfortunately, in the US it would be Isoda, which is another cable.
In 1992, or so, Goertz introduced their two flat strips, which they patented. Now that the patent has run out, we are using it as it is far less labour intensive the coax solution and it sounds better as it uses very little PTFE as the insulator. There is an unmistakable purity about the sound when impedance matched speaker cables are employed.