A crossover design featuring a 24-decibel per octave roll-off constructed by combining two-second order 12-decibel per octave Butterworth low-pass filters. The Linkwitz-Riley design is commonly used in speakers and particularly in subwoofers and subwoofer outputs. It results in in-phase outputs that roll-off quickly and minimize lobing (where two speaker drivers on either side of a crossover frequency both still output signals over a range of frequencies close to the crossover frequency).