Many high end speaker manufacturers (e.g., Vandersteen, Wilson) set back the mid-range and tweeter to adjust for so-called time delay. Why doesn't B&W bother with this?
In an earlier version they did just that but they changed to this tweeter forward design. If memory serves me well the explanation given was something along these lines. The earlier version did use an acoustical 24 dB per octave filter which require that the drivers are connected with the same polarity, if the drivers are at the same distance from the listener. Then B&W decided to go for minimum component 6dB per octave crossover. Because the drivers have their own roll off they ended with a 12 dB or 18 dB acoustic crossover slope. A crossover with these slopes require the drivers to be connected with opposite fase
Sorry I pressed “post” by mistake so I will go on. However the development team came to the conclusion that instead of putting the tweeter in opposite phase compared to the midrange they could run both with the same polarity and the push the tweeter forward by half the wavelength at the crossover frequency, which gives the same effect (putting it 180 degrees out of phase) but holds the advantage that the tweeter is freed from diffraction and the acoustic shadow of the midrange cabinet/housing. Greetings from Denmark.
You do not need refraction behind the speaker,the only time you can is if you have rear firing drivers and in this case you don’t,put them out in the room if you want them to do what the are designed for,read about acoustical treatments and learn 🥴
