Speaker Crossover Component Calculator
Work out the capacitor and inductor values for a simple first-order passive crossover. Enter the crossover frequency you want and the driver impedance, and the tool returns the series capacitor that feeds a tweeter (high-pass) and the series inductor that feeds a woofer (low-pass).
Enter Values
How to use this calculator
- Enter the crossover frequency Fc in hertz — the point where the tweeter and woofer hand over (often 2000–3500 Hz).
- Enter the driver's nominal impedance in ohms, usually 4, 6 or 8 Ω as marked on the driver.
- Read the capacitor value (µF) for the tweeter and the inductor value (mH) for the woofer, then pick the nearest standard component values.
How it works
A first-order crossover uses one component per driver. The high-pass capacitor for the tweeter is C = 1,000,000 ÷ (2π × Fc × R), giving microfarads. The low-pass inductor for the woofer is L = 1000 × R ÷ (2π × Fc), giving millihenries. Both roll off at 6 dB per octave from the crossover frequency, and both use the driver impedance R at that frequency.
Worked example
Worked example. For a crossover at 2500 Hz into 8 Ω drivers: C = 1,000,000 ÷ (2π × 2500 × 8) = 7.958 µF for the tweeter, and L = 1000 × 8 ÷ (2π × 2500) = 0.5093 mH for the woofer.
Common mistakes
- Using the nominal impedance when the real impedance rises well above it near the crossover — a tweeter marked 8 Ω can be 10–15 Ω there, shifting the actual crossover point.
- Assuming a first-order network gives good driver protection; its gentle 6 dB/octave slope lets a lot of low-frequency energy reach the tweeter.
- Ignoring the woofer's voice-coil inductance, which adds its own roll-off and interacts with the crossover inductor.
Frequently asked questions
Why choose a first-order crossover?
It uses the fewest parts, is cheap, and is phase-coherent when the drivers are aligned. The trade-off is the shallow 6 dB/octave slope, so both drivers overlap over a wide band and the tweeter sees more low-frequency energy.
What component voltage and tolerance should I use?
Use non-polarised film capacitors and air-core inductors for the best sound, with tolerances of 5% or better. Pick the nearest standard value to the calculated figure, or combine parts in series/parallel to get closer.
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