Speaker Crossover Frequency Calculator
A passive crossover splits the audio signal so each driver only receives the band it handles well. A first-order network uses a single component per driver and rolls off at 6 decibels per octave, with each filter 3 decibels down at the crossover frequency. This calculator computes the high-pass capacitor and the low-pass inductor for a first-order crossover from the crossover frequency and the driver impedance you enter, returning the capacitor in microfarads and the inductor in millihenries. Use the driver's nominal impedance so the values match your hardware.
First-order crossover formula
High-pass capacitor C = 1 / (2 pi f R)
Low-pass inductor L = R / (2 pi f)
Microfarads = C * 1,000,000
Millihenries = L * 1,000
f is the crossover frequency in hertz and R the driver impedance in ohms. The capacitor passes highs to the tweeter; the inductor passes lows to the woofer.
Crossover context
- First-order networks roll off at 6 decibels per octave, the gentlest standard slope.
- Higher impedance means a smaller capacitor and a larger inductor for the same frequency.
- Real driver impedance rises with frequency; a Zobel network can flatten it.
- Steeper second- and third-order designs use more components per driver.
- Match the crossover point to each driver's usable bandwidth.
Crossover frequency: frequently asked questions
What is a crossover frequency?
The crossover frequency is where a passive crossover network splits the audio signal between drivers, for example sending highs to a tweeter and lows to a woofer. At a first-order crossover the response of each filter is 3 decibels down at the crossover point and rolls off at 6 decibels per octave.
What are the first-order component formulas?
For a single-component, first-order filter: the high-pass capacitor is C = 1 / (2 pi f R), and the low-pass inductor is L = R / (2 pi f), where f is the crossover frequency in hertz and R is the driver impedance in ohms. This calculator returns both in microfarads and millihenries.
Why does driver impedance matter?
The filter component value scales directly with impedance: a higher-impedance driver needs a smaller capacitor and a larger inductor for the same crossover frequency. Use the driver's nominal impedance (commonly 4 or 8 ohms), entered as a user input so the calculation matches your hardware.
What is the slope of a first-order crossover?
A first-order crossover rolls off at 6 decibels per octave, the gentlest standard slope. It uses one component per driver and preserves phase well, but offers less protection against out-of-band frequencies than steeper second- or third-order designs.
Are these values exact for a real driver?
They are the textbook resistive-load values. Real drivers have impedance that rises with frequency and a reactive component, so designers often add a Zobel network or measure the impedance. Treat these as the correct starting point and refine by measurement.
Official sources
- Acoustical Society of America: ASA audio and electroacoustics resources.
- National Institute of Standards and Technology: NIST electrical and acoustic measurement.
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.