crossover point and type ?s

[deadbroke]

so if i pick a butterworth type crossover for my lowpass and high pass at my crossover point both drivers will be at -3db but the sum of both drives would give me a 3db increase. why would i want an increase of sound at my crossover point. i'm assuming this is why some people decide to do lowpass at say 100hz and highpass a few hz more so the sum of the rolloff would be flat? in my mind i am thinking at the crossover point one driver is playing half as loud and the other driver is playing the other half to sum itself to 0db. why not just do a linkwitz-riley so you sum at 0db and not worry about what frequency to pick up on your highpass