Standing mounted speaker positioning

[Abtr]

I don't know about B&W, but KEF advices that their LS50 speakers be placed on 65 cm stands which positions the (coaxial) tweeter about 20cm lower than my ears when I sit in a normal chair (IKEA Poäng). Maybe the bass response and slight off-axis mid/high response of the KEFs is supposed to be best at 65 cm, though I personally use them at 72 cm stands (with tweeters 13 cm lower than my ears).. I think you'll have to try what works best with the B&Ws.. I guess you could tilt the speakers but that would only work for a listening position at a specific distance..