Practical tools for measured work
Passive Speaker Crossover Calculator
Calculate starter inductor and capacitor values for a first- or second-order passive speaker crossover.
Woofer-to-tweeter frequency for 2-way; woofer-to-midrange for 3-way.
Used only in 3-way mode and must exceed the lower crossover.
Used only in 3-way mode.
12 dB/octave ideal reference sections. In 3-way mode the midrange HP and LP are separate design references, not parts to concatenate without a full network simulation.
How it works
What this calculates: starter inductor and capacitor values for an ideal resistive two-way crossover, or separate target-corner references for the branches of a prospective three-way design. Three-way output is deliberately not presented as a finished combined network.
Method. With angular frequency omega = 2 pi f, first-order low-pass inductance is L = R / omega and high-pass capacitance is C = 1 / (R omega). The second-order values use Q = 1 / sqrt(2): low-pass L = R/(Q omega), C = Q/(R omega); high-pass uses the dual network.
Worked check. At 2,500 Hz into an ideal 8-ohm driver, a first-order low-pass needs about 0.509 mH and the matching high-pass needs about 7.96 uF. Select nearby real component values only after measuring the drivers and modeling their acoustic response.
Current-input example
The result above uses these exact values. This snapshot is included when the page is printed so the output can be checked against the original measurements.
- Reference layout
- 2-way crossover
- Electrical order
- 2nd order Butterworth (12 dB/oct)
- Crossover frequency
- 2500 Hz
- Upper crossover (3-way)
- 5000 Hz
- Woofer nominal impedance
- 8 ohm
- Midrange nominal impedance
- 8 ohm
- Tweeter nominal impedance
- 8 ohm
Primary result: 2500 Hz LP series: 0.720 mH.
Before using the result
- Measure from the datum or reference edge described by this tool, and do not mix inside, outside and centerline dimensions.
- Keep inputs in the displayed units and preserve more precision than the final cutting or purchasing tolerance requires.
- When the result is close to a limit, verify it with a test piece, field measurement, manufacturer drawing or qualified project professional.
Limitations
These are ideal electrical starting values, not a finished loudspeaker design. A loudspeaker's impedance changes with frequency and its cone, enclosure, baffle, sensitivity, acoustic offset and natural roll-off all alter the summed response.
For a three-way design, the displayed midrange high-pass and low-pass are independent reference sections. Cascading them changes their loading and Q; do not simply join the displayed parts. Model the complete interacting band-pass network with measured impedance. The calculator does not add impedance compensation, response shaping, level matching, driver-protection analysis or component parasitics.
Frequently asked questions
Why are nominal ohms only a starting point?
The printed 4- or 8-ohm rating is not a flat resistance. The real impedance curve changes around resonance and across the passband, shifting the electrical corner produced by fixed parts.
Can I directly combine the two midrange rows?
No. They show the two target corner references. A real passive band-pass is an interacting network, so use measured impedance and a circuit/acoustic simulator to combine and optimize it.
Is a second-order passive network automatically Linkwitz-Riley?
No. This page calculates Butterworth electrical sections. A Linkwitz-Riley label describes the resulting crossover alignment; achieving it acoustically requires the driver responses and their physical alignment to be included.
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