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Passive Crossover Design Calculator

C1 equals 0.159 divided by R sub H times f; L1 equals R sub L divided by 6.28 times f
Ω
Ω
Hz

Solution

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1st Order Butterworth Crossover

The simplest crossover design with a 6 dB/octave roll-off slope. Minimal phase shift but a wide driver overlap band.

C₁ = 0.159 / (R_H × f), L₁ = R_L / (6.28 × f)

2nd Order Crossover

12 dB/octave slope with multiple alignment choices: Butterworth, Linkwitz-Riley, Bessel, and Chebychev.

C = k_C / (R × f), L = k_L × R / f

3rd Order Butterworth Crossover

18 dB/octave roll-off for tighter frequency separation. Good for protecting tweeters from low-frequency power.

C₁ = 0.1061 / (R_H × f), L₁ = 0.1194 × R_H / f

4th Order Crossover

Steepest 24 dB/octave roll-off with excellent driver isolation. Available in Linkwitz-Riley, Bessel, Butterworth, Legendre, Gaussian, and Linear-Phase alignments.

C = k_C / (R × f), L = k_L × R / f

How It Works

A passive crossover network splits an audio signal into separate frequency bands for different speaker drivers. The crossover uses capacitors and inductors to create high-pass and low-pass filters. The filter order determines the roll-off slope: 1st = 6 dB/octave, 2nd = 12 dB/octave, 3rd = 18 dB/octave, 4th = 24 dB/octave.

Example Problem

Design a 1st-order Butterworth crossover at 3,000 Hz with R_H = 8 Ω (tweeter) and R_L = 4 Ω (woofer).

  1. Capacitor: C1 = 0.159 / (8 × 3000) = 6.625 × 10⁻⁶ F (6.625 μF)
  2. Inductor: L1 = 4 / (6.28 × 3000) = 2.1231 × 10⁻⁴ H (0.212 mH)

Higher-order networks produce more components with different coefficients.

Key Concepts

Passive crossover networks use frequency-dependent impedance of capacitors and inductors to split an audio signal into bands. The filter order (1st through 4th) determines roll-off steepness: 6, 12, 18, or 24 dB/octave. Higher orders provide better driver isolation but add complexity and component count. Different alignment types (Butterworth, Linkwitz-Riley, Bessel, Chebychev) trade off between flat amplitude response, phase behavior, and transient response.

Applications

  • Home audio: designing two-way and three-way passive speaker crossover networks
  • Car audio: building custom crossovers for component speaker systems in vehicles
  • Studio monitors: matching crossover design to driver specifications for accurate sound reproduction
  • PA systems: calculating component values for high-power passive crossovers in live sound equipment

Common Mistakes

  • Using nominal impedance instead of actual driver impedance at the crossover frequency — impedance varies with frequency and can differ significantly from the rated value
  • Choosing a crossover frequency outside the drivers' overlap range — both drivers must operate comfortably at the crossover point
  • Ignoring component tolerances — capacitor and inductor values in audio applications should be within 5% to maintain the designed response curve
  • Mixing crossover types between high-pass and low-pass sections — both filters must use the same alignment (e.g., both Linkwitz-Riley) for proper summation

Frequently Asked Questions

What is a passive crossover network?

A passive crossover network uses non-powered components (capacitors and inductors) to divide an audio signal by frequency. Unlike active crossovers, passive crossovers sit between the amplifier and the speaker drivers, requiring no external power supply.

What is the difference between Butterworth and Linkwitz-Riley crossovers?

A Butterworth crossover is −3 dB at the crossover frequency, meaning each filter passes half power at that point. A Linkwitz-Riley crossover is −6 dB at crossover, so when the outputs are summed acoustically, the result is perfectly flat.

How do I choose the right crossover frequency?

The crossover frequency should fall within the operating range of both drivers. Tweeter crossover frequencies are typically between 2,000 Hz and 5,000 Hz for two-way systems.

Why do the results show values in farads and henrys?

Farads (F) measure capacitance and henrys (H) measure inductance. In audio crossovers, typical values are in the microfarad (μF) range for capacitors and millihenry (mH) range for inductors.

Can I use this calculator for three-way speaker systems?

This calculator computes component values for a two-way crossover network. For a three-way system, design two separate two-way crossovers: one between the woofer and midrange, and another between the midrange and tweeter.

Reference: Dickason, Vance. 1991. The Loudspeaker Design Cookbook. Audio Amateur Press. 4th ed.

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