Linn amp and REL sub

If you're LK 85's are set up to be used in active configuration, they should be used with the intended speakers for the active cards. If you want, you could remove the active cards and use the amps to power your sub, and then yes, BFA's are just another type of speaker wire connectors.

extra action, did you ever connect this? with the rel sub, you have the neutrix connector that has 3 wires. check out rel.net for the instructions. 1 wire to black and 1 wire to red on the right speaker, then the yellow wire goes to the left speaker either on the red or black.