We have discussed acoustic centers before - see post 4430 Studio Monitor.

As to baffle spacing - keeping the drivers as close togethor to each other is best. It reduces comb filtering interferance, shifting crossover nulls further off axis and time delay between drivers. You can calculate exact vectors where the two sound sources are in cancellation around 180o, if that is the sort of thing you want to do. Keep them as close as possible though.

Calculation of wavelength is speed of sound/frequency.

Speed of sound is 344 meters/second which will get you wavelength in meters. 13548inch/sec is speed of sound in inches, which will get you wavelength in inches.

800Hz wavelength is 16.94"

Adrian