The best speaker cable I’ve ever owned was the old Townsend Isolda. These were based on your Goertz flat ribbons (zobels and such) but different insulation and cryo’d. Imaging was huge, treble was sweet, and the bass was un-be-lie-vable. Like adding a subwoofer. It was ridiculous! I regret selling them years ago. They’ve been replaced by the Fractals which I presume are even better, but they’re much more expensive.
Anyway, some time ago but more recently, I did a huge cable loom loan from fatwyre and tried out the MI2 hoping that they might be similar to the Isolda yet cheaper. But they couldn’t be less similar. I found them lousy with almost no standout qualities! I compared them to similar priced cables from Zu, Cardas, Kimber, Nordost, DH Labs, Black Cat, and Audience AU24. Audience and Black Cat (Morpheus I think) were top of the pile, sounding quite similar but I got RF interference from the Black Cat where I lived so went with the Audience.
So a long post to affirm finding the Goertz unimpressive, but I’d be curious to see if more recent Black Cats might retain those good qualities. Vouching obviously still for the Audience (though more expensive). All the others I thought were forgettable. It's hard for me to say what impact the Zobels alone had on my old system, but my current amp and speakers (both ATC) for sure don't need these impedance circuits on speaker cables.