Fourth-Order Linkwitz-Riley (24 dB/octave)

Most common professional crossover order.

Implementation: Cascade two Butterworth 12 dB/octave sections at same frequency.

Component values for each 2nd-order stage:

Stage 1 (Q = 0.5):

L₁ = R / (2π × f_c × 0.5)
C₁ = 0.5 / (2π × f_c × R)

Stage 2 (Q = 0.5 × same):

(Same values — both stages identical for LR4)

Properties: - At crossover: Each section = −6 dB - Phase: HPF = 360° (in phase), LPF = 360° - Sum: Flat response when both drivers in polarity - No polarity reversal needed

This is why LR4 became the standard for professional audio crossovers.