what is the best speaker cables for martin logan

You could consider the Blue Circle BC92. Blue Circle's Gilbert Yeung is a Martin Logan owner and uses then as his reference to design his gear.

There is no such thing as the "best cable" it all depends on your taste and the rest of your system. I like Harmonic Tech Pro-9 plus. Cardas and Audioquest are also good choices but may cost a bit more. I suggest you borrow some and try them in your system.

I have tried harmonic tech and liked the sound, but prefer my cheaper alphacore goertz MI2 biwire cables. They seem to soften the somewhat dry and analytical sound of the logans (quest z's). Associated equipment include EAD PM 2000, which I love, a sub-standard marantz DVD player, and a sub-standard Yamaha DSP 3090 (Can't affort to upgrade yet). Hope this helps.