Speaker Crossover Frequency Calculator
A passive crossover sends low frequencies to the woofer and high frequencies to the tweeter, with the crossover frequency marking the handover point. The simplest design is first-order: a single capacitor for the high-pass leg and a single inductor for the low-pass leg, each rolling off at 6 decibels per octave. This calculator works in both directions. Enter a capacitor and inductor value with the driver impedance to get the crossover frequencies, or enter a target frequency to get the component values you need. The nominal impedance is editable to match 4-ohm or 8-ohm drivers.
First-order crossover formula
High-pass (capacitor): f = 1 / (2 * pi * R * C)
Low-pass (inductor): f = R / (2 * pi * L)
Capacitor for target f: C = 1 / (2 * pi * R * f)
Inductor for target f: L = R / (2 * pi * f)
R is the driver impedance in ohms, C is capacitance in farads, and L is inductance in henries. The calculator converts microfarads and millihenries to base units internally. First-order filters roll off at 6 decibels per octave.
Worked example
An 8-ohm tweeter with a 10 microfarad capacitor crosses over at f = 1 / (2 * pi * 8 * 0.00001) = 1,989.44 Hz. To cross at 2,500 Hz on an 8-ohm driver you need C = 1 / (2 * pi * 8 * 2,500) = 7.96 microfarads, and a low-pass inductor L = 8 / (2 * pi * 2,500) = 0.51 millihenries.
Crossover frequency: frequently asked questions
What is a speaker crossover?
A crossover is a filter network that splits an audio signal into frequency bands and routes each band to the driver best suited to it: low frequencies to the woofer, high frequencies to the tweeter. The crossover frequency is the point at which the filter has reduced the signal by 3 decibels, where the two drivers hand over.
What is the first-order crossover formula?
For a single capacitor high-pass or single inductor low-pass feeding a driver of impedance R, the crossover frequency is f = 1 divided by (2 times pi times R times C) for a capacitor, and f = R divided by (2 times pi times L) for an inductor. This calculator covers the first-order (6 dB per octave) case for both.
What capacitor or inductor do I need for a target frequency?
Rearrange the formula. For a high-pass capacitor: C = 1 divided by (2 times pi times R times f). For a low-pass inductor: L = R divided by (2 times pi times f). Enter your target frequency and impedance and this calculator returns both component values alongside the resulting frequency.
Does driver impedance stay constant?
Real drivers have impedance that varies with frequency, so the nominal impedance (often 4 or 8 ohms) is an approximation. For precise passive crossover design, impedance compensation networks are used. Treat the result as the textbook first-order target and verify with measurement.
Official sources
- U.S. National Institute of Standards and Technology: nist.gov (electrical units and constants).
- NIST Reference on Constants, Units, and Uncertainty: SI units.
Reviewed by the CalculatorHub team, edited by James Graham, 19 June 2026. See our methodology.