Crossover Calculator

A speaker crossover divides an audio signal so each driver receives the frequency range it is intended to reproduce. In a simple two-way passive network, a series capacitor creates a first-order high-pass path for the tweeter and a series inductor creates a first-order low-pass path for the woofer. At the selected crossover frequency, each ideal branch has a reactance equal in magnitude to the nominal speaker impedance, producing the familiar six-decibel-per-octave electrical slopes. The capacitor equation is one divided by two pi times frequency times impedance. This calculator converts the result from farads to microfarads. The inductor equation is impedance divided by two pi times frequency, with the result converted from henries to millihenries. Frequency is entered in hertz and impedance in ohms. Raising crossover frequency reduces both required component values. Raising impedance reduces the capacitor value but increases the inductor value. These calculations describe ideal first-order filters driven by a resistive load. A real loudspeaker does not maintain one fixed impedance across frequency. Voice-coil inductance, enclosure loading, resonance, and the driver's mechanical and electrical behavior all change its impedance and acoustic output. The driver's natural response, physical offset, polarity, and listening-axis phase also influence the combined response. Therefore, a component pair that is mathematically correct may not create an acoustically flat crossover without measurement and adjustment. Choose standard component values near the calculated targets and use parts with suitable voltage, current, resistance, and power ratings. Film capacitors are common in signal paths, while crossover inductors should have low enough series resistance for the design. Avoid choosing a crossover outside a driver's safe operating band. Tweeters in particular may require a steeper filter or a higher crossover frequency to limit excursion and heating. Use this result for preliminary design, then verify the network with impedance data, frequency-response measurements, simulation, and listening tests. More advanced second-, third-, and fourth-order alignments require additional components and different coefficients, so their values should not be inferred directly from this first-order calculator.