“Having had the original black speaker cable, I bought the Black II to biwire my Elac speakers.

Not sure what you did. The Black II is like a more sophisticated version of the original, better bass, more open midrange, more refined treble. Above all just a more communicative cable

I notice the differences by swapping them around (bass to treble etc)

I’m actually shocked enough to contact you. People seldom get the credit they deserve”