Speaker crossover calculator
Exact component values for passive 2-way crossovers — with the nearest standard E12 parts, tweeter L-pad, and an optional Zobel network. Formulas in the open.
Values assume the driver impedance you enter is what the driver presents at the crossover frequency. Real impedance rises with frequency — use measured values or add the Zobel to flatten the woofer first.
High-pass → tweeter
| Part | Exact | Nearest E12 | off by |
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Low-pass → woofer
| Part | Exact | Nearest E12 | off by |
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Choosing a filter type
- Linkwitz-Riley 2nd order — the default for good reason: both drivers are −6 dB at crossover and sum flat when wired with the tweeter's polarity inverted.
- Butterworth 2nd order — maximally flat individually, but sums with a +3 dB bump at crossover; some designs use it deliberately.
- Bessel 2nd order — best transient behavior of the second-order family, gentler knee.
- Butterworth 3rd order — steeper 18 dB/oct protection for fragile tweeters; sums flat with drivers in normal polarity.
- 1st order — only one component per driver and perfect phase in theory, but 6 dB/oct sends real power to the tweeter well below crossover. Use high crossover points and robust tweeters.
The math
Second-order sections come from the filter Q: C = Q / (2πfR), L = R / (2πfQ), with Q = 0.5 (Linkwitz-Riley), 0.707 (Butterworth), 0.577 (Bessel). Third-order Butterworth uses the standard ladder constants (0.1061, 0.1194, 0.3183 / 0.2387, 0.2122, 0.0796). The L-pad holds the tweeter's load constant: R₁ = Z(1−k), R₂ = Z·k/(1−k) with k = 10^(−dB/20). Zobel: R = 1.25·Re, C = Le/R².
FAQ
Why is my 4th-order Linkwitz-Riley not here?
Because passive LR4 done honestly needs impedance-compensated drivers and verified tables; a wrong LR4 is worse than a right LR2. It's on the roadmap with proper validation.
Do I really need to invert the tweeter on LR2?
Yes — at crossover the two 2nd-order sections are 180° apart; inverting the tweeter brings them into phase so the outputs sum flat instead of cancelling into a notch.
Capacitor and inductor quality?
Film capacitors and air-core inductors drift least. E12 tolerance (±10%) shifts the corner a few percent — audible mostly as a small level change near crossover; parallel/series-combine parts if you want closer than E12.