Crossover Slope

How steeply a crossover fades each driver out, in dB per octave.

A 12dB/octave slope halves output every octave past the crossover point twice over; 24dB/octave is twice as steep again. Steeper slopes hand off more abruptly and overlap less; shallower slopes blend more gradually but ask more of each driver outside its comfort zone. AVR bass management typically uses 12dB/oct high-pass and 24dB/oct low-pass.