Why do you think Bi-Wiring improves the sound ?

So Alan Shaw says it doesn't matter and Richard Vandersteen says it absolutely matters. Two very respected speaker designers with completely different views of the same subject. Do you just cherry pick one because it supports what you believe or fits your experience? What a logical fallacy. I would not add a set of binding posts to a set of speakers just to try it out. If there are already two sets of binding posts, give it a try for yourself and make your own decision.

The terminals were fitted for one reason and one reason only: to give the user choice. Have I ever used them at exhibitions? No. Have I ever used them for critical listening? No. Have I ever used them during the design of the speaker? No. When we were offering the biwire terminals, right at the end of the design process (which has all been with single wire) I took a saw to the prototype PCB, cut in in half to isolate the bass and tweeter sections and then made a pretty PCB layout based on that. Did I listen to the biwired crossover before authorising production? No. Do I believe that even 0.00000001% of enhanced performance can be gained? No. 

This sure sounds like hard science. Lots and lots of "I believe" in there. He couldn't even be bothered to listen to it. It is no more authoritative than Vandersteen's anecdotal evidence. Is there any evidence that Richard Vandersteen does not use science in his designs? I would say that quite the opposite is true. In fact, he would say that designers that choose to not pay attention to phase in their speakers are absolutely wrong. He does back that with measurements. I am not saying either is right or wrong. I am just pointing out that many people here love to pick out the expert that they want to believe. You know, appeal to authority.