Enter high and low pass speaker impedances. Enter desired crossover frequency. On the second-order crossover calculator you must select type of crossover. Phase shift on a first-order crossover is 90 degrees.
Butterworth crossovers yield to a peak at the crossover frequency.
Bessel crossovers have a frequency response between Linkwitz-Riley and Butterworth crossovers. Ohms An L-pad circuit will attenuate a speaker. The power delivered by the amplifier remains constant. Since L-pads are made from resistors, it does not induce any phase shifts, or affect frequency response.