I have some miscellaneous split ferrite beads I wish to use as RFI chokes on some long speaker cables. I checked them with my antenna MFJ antenna analyzer to see what they do on the bands I work. What is the important parameter here, Rs or Xs? (I'm thinking that Xs only changes the resonate frequency of a line, Rs is what kills the RF.) So do I want high Rs, high Xs, or both?
Either, but in common-mode choke applications if I had a choice I would lean towards a ferrite with significant R component. Fair-Rite mix 31 is a very good modern choice.
In any event, multiple turns of the speaker cable pair through a bead/toroid is the way to rack up impedance fast. If you can't get multiple turns through, you may need a long stack of beads.