How this calculator works
Passive networks require the driver impedance to behave approximately like a resistance around the crossover. The two-way table lists elements from amplifier to driver; shunt parts connect to the return. First- and second-order values follow ideal circuit equations. Third- and fourth-order values and three-way tables use the cited published coefficients, with their tabulated precision. Three-way networks support frequency spreads of 8 or 10 and require the referenced circuit, rather than independent cascaded filters. Specialised families use the published-coefficient mode so their coefficients and circuit remain explicit. Zobel compensation places a series RC across the driver. L-pad values preserve the stated input resistance with a resistive driver.
Formula
First order: L = R/(2 pi f), C = 1/(2 pi f R). Second order: L = R/(2 pi f Q), C = Q/(2 pi f R), with Q = 1/sqrt(2) for Butterworth, 1/sqrt(3) for Bessel, or 0.5 for Linkwitz-Riley. Here f is the natural pole frequency; section levels at f are about -3.01, -4.77 and -6.02 dB respectively. Published tables: L = kL R/f, C = kC/(R f). Zobel: Rz = R, Cz = Lvoice/R². L-pad: a = 10^(dB/20), Rs = R(1-1/a), Rp = R/(a-1).
Worked example
For an 8 ohm first-order two-way crossover at 1000 Hz, the woofer series inductor is 0.00127324 H and the tweeter series capacitor is 0.0000198944 F. Attenuating an 8 ohm driver by 6.0206 dB uses 4 ohms series and 8 ohms shunt.
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Frequently asked questions
Can I use nominal speaker impedance?
Only as a rough starting estimate. Measured impedance, resonant peaks and acoustic response affect the real crossover. Impedance correction may be needed.
Which driver polarity should I use?
For the cited three-way tables, second order reverses the midrange and the other offered orders use normal polarity. Two-way second-order pairs normally reverse one driver. Verify the full acoustic sum and the reference circuit.
How do I enter a published coefficient table?
Choose the published-coefficient mode and add one row per capacitor or inductor, with the coefficient from the source in C = k/(R f) or L = k R/f.