Bass Crossover, how exactly do you use it for best effect?

[Canada]

I have B&W 683 front left and right speakers I also have a Velodyne DLS 4000R subwoofer I have my the crossover on my Pioneer receiver set as 80 hrz. Is that where I should have it set or should it be set higher. If I set the crossover to on my receiver higher will my front left and right speakers still be getting that signal or will it by pass my front speakers and be sent to my subwoofer exclusively.