Speaker Crossover Calculator (1st & 2nd Order, Butterworth / Linkwitz-Riley)
Capacitor and inductor values for a passive two-way speaker crossover — 1st-order 6 dB or 2nd-order 12 dB Butterworth and Linkwitz-Riley — from crossover frequency and woofer/tweeter impedance.
How it works
1st order: C = 1 ÷ (2πfZ), L = Z ÷ (2πf). 2nd order: C = k_C ÷ (2πfZ), L = k_L × Z ÷ (2πf) with Butterworth k = 0.707 / 1.414, Linkwitz-Riley 0.5 / 2.0, Bessel 0.577 / 1.732
A passive crossover splits the amplifier signal so the woofer gets the lows and the tweeter the highs, using the frequency-dependent impedance of capacitors and inductors. A single series capacitor or inductor gives a first-order filter that rolls off 6 dB per octave — simple and phase-friendly but with wide overlap that can stress the tweeter. Adding a shunt element makes a second-order 12 dB filter; the ratio of the two values sets the alignment: Butterworth is −3 dB at the crossover so the sum bumps up 3 dB, while Linkwitz-Riley is −6 dB per section and sums perfectly flat, which is why it is the most popular choice. Both second-order types put the drivers 180° apart, so the tweeter is wired with reversed polarity. Real drivers are not resistors, so treat these as starting values and measure or listen.
Worked example
A 2.5 kHz Linkwitz-Riley crossover with 8 Ω drivers: tweeter 3.98 µF series + 1.02 mH parallel; woofer 1.02 mH series + 3.98 µF parallel.
Frequently asked questions
Why does the calculated value differ from a commercial crossover?
Designers use the drivers’ measured impedance and response, add baffle-step and level padding, and often stagger the woofer and tweeter frequencies. The textbook values are the starting point.
What about third-order?
Third-order (18 dB) Butterworth uses three elements per section and sums flat with drivers 90° apart; it is common in tweeters that need steep protection.
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This calculator is for educational purposes. Double-check important results before acting on them.