what speaker cable do you use on the Evolution Acoustics MM3 speakers or Harbeth speakers.

Fidelis AV which is the national distributor for Harbeth uses Tellurium Q Silver Diamond speaker cable.

Clear Day Cables Shotgun speaker cables with my MM3’s. Great cables and better seller.

Cerious technologies Graphene extreme speaker cables with Harbeth are exceptional.

With Harbeth, you'll definitely not want warm leaning cables.  Silver cables could be a possibility, but sometimes they're a bit lean.  For my P3ESR, after a few iterations, I ended up sticking with Furutech cables and they're a very synergistic match.  I went DIY, with the Alpha-S14 cable and terminated with Furutech rhodium banana plugs crimped with WBT sleeves.  This is their alpha OCC wire, and essentially the same as the Speaker Reference III line, but smaller gauge.  Not a warm cable, maybe slightly sweet through the mids (like Harbeths as well), and plenty of detail and openness. For this particular system, the price and performance was right. 

Harbeth's owner and designer Alan Shaw says that you do not need anything special. Any cable of sufficient thickness for the length will be fine. He occasionally uses ordinary electricity flex for demos. I think he is right, although it helps if the two strands are colour coded or have some ridge to avoid polarity confusion. That is really all there is to it.

You don't need anything special per se, but you can certainly affect the final sound based on your choice of cable.  I suppose the OP was asking about synergistic options.  I went through a few different options and found one that I really liked with the Harbeths, several that I didn't.

If cables have a sonic signature there is something wrong with them. Fortunately, even cheap ordinary cables can be completely neutral, unilke many boutique cables.

I upgraded to Synergistic Atmosphere speaker cables for the Harbeth and find the system has a bigger soundstage and yet very detailed and cohesive sounding

Upgraded to Tara Labs “The Muse”.

Very happy with Gabriel Gold Reflection V2 with the Evolution Acoustics.

Look at Furutech cables i am selling they would work great with these speakers.