First Hand Experience: I’ve owned my B&W 801-S2’s for over 25 years, and have tried on 3 separate occasions to "improve" them with bi-wiring. It seems that about every 10 years I need to re-prove it to myself. Each time, the resulting sound was phasey and less coherent. The 801’s have great driver integration. You don’t hear woofer+mid+tweeter. They gel into single voice very nicely, and that falls apart with bi-wiring....... every time. I even lived with them bi-wired for a couple weeks to get accustomed to that sound, and I did.... until I went back to single wire, and they suddenly sounded more correct.
It all comes down to HOW WAS IT DESIGNED!! If the designer voiced the crossover with bi-wiring, then OF COURSE it’s going to sound more correct that way. But what stupid designer would do that, when only a very small percentage of users will bi-wire?
Just last year, I finally upgraded my 801’s binding posts, and converted them to using only 1 pair of higher quality terminals. I have performed many other crossover mods on them over the years that have improved these 801’s greatly, but bi-wiring is NOT one of them.