Speaker Crossover Calculator

Calculate speaker crossover component values from frequency and impedance. Includes formulas, examples, assumptions and practical design limitations.

Quick answer

Enter your crossover frequency and nominal driver impedance. The calculator returns capacitor and inductor values for first-order (6 dB/octave) and second-order Butterworth (12 dB/octave) passive networks. These are electrical starting points — real drivers require measurement and adjustment before finalizing component values.

How this calculator works

The speaker crossover calculator gives starting capacitor and inductor values for simple 2-way passive networks at your chosen crossover frequency and nominal impedance. It suits DIY loudspeaker projects where you need approximate parts before modeling with measured driver impedance and frequency response.

First-order (6 dB/octave) series components are exact for a purely resistive load. Second-order Butterworth values are approximate starting points for HP/LP pairs. Real drivers are not resistors — Zobel networks, L-pads, and steeper slopes are often required for smooth acoustic summing.

Formulas used

  • First-order tweeter high-pass capacitor: C = 1 / (2π × f × R)
  • First-order woofer low-pass inductor: L = R / (2π × f)
  • Second-order Butterworth HP: series C = C₁/√2, shunt L = L₁/√2
  • Second-order Butterworth LP: series L = L₁ × √2, shunt C = C₁ × √2
  • f = crossover frequency (Hz), R = nominal impedance (Ω)

Worked example

Crossover at 3 kHz with 8 Ω nominal impedance:

  • First-order tweeter C = 1 / (2π × 3000 × 8) ≈ 6.63 µF
  • First-order woofer L = 8 / (2π × 3000) ≈ 0.42 mH
  • Second-order HP: series C ≈ 4.69 µF, shunt L ≈ 0.30 mH
  • Second-order LP: series L ≈ 0.60 mH, shunt C ≈ 9.37 µF

Use standard component values (E12 or E24 series) and measure acoustic response with both drivers mounted before finalizing.

Impedance assumptions

Crossover formulas treat the driver as a fixed resistor. In practice, driver impedance rises at resonance (by 5–20 ×) and at high frequencies (due to voice coil inductance). This shifts the actual acoustic crossover point away from the calculated value. Use measured impedance curves and add a Zobel network (RC shunt) to flatten impedance in the crossover region if accuracy matters.

Why real drivers need measurement

Component values from this calculator set the electrical crossover. The acoustic crossover — what you hear — also depends on the driver's on-axis frequency response, its baffle step behaviour and polarity. Two identical electrical crossovers will sound different in different cabinet and driver combinations. Always measure and iterate.

Key terms

  • Crossover frequency — electrical −3 dB split point between drivers.
  • First order (6 dB/oct) — one series component per driver leg; simple but has wide overlap region.
  • Second order (12 dB/oct) — two components per leg; steeper separation, phase shift of 180° across band.
  • Nominal impedance — design reference resistance, commonly 4 Ω or 8 Ω.
  • Capacitor (high-pass) — blocks low frequencies from the tweeter.
  • Inductor (low-pass) — blocks high frequencies from the woofer.

Related tools

Frequently asked questions

  • What does a crossover calculator calculate? Starting capacitor and inductor values for high-pass (tweeter) and low-pass (woofer) legs at a given frequency and nominal impedance.
  • First-order or second-order crossover? First-order is simpler and has better impulse response but a wider overlap region. Second-order separates drivers more sharply but requires polarity checking to avoid cancellation at the crossover point.
  • Can I use these values directly? Only as a starting point. Measure driver impedance and SPL, then adjust component values for flat acoustic summing and adequate driver protection.
  • Why does impedance matter? Component values assume a resistive load. Real driver impedance varies with frequency, shifting the acoustic crossover away from the calculated electrical point.
  • What is baffle step? A 6 dB midrange rise when the cabinet becomes large relative to the wavelength. Without compensation, the speaker will sound thin at the crossover region. Use the baffle step calculator to estimate and compensate.