# Crossover Calculator

Calculate audio crossover component values for speaker networks. Find capacitor and inductor sizes for 1st and 2nd order Butterworth crossovers.

## What this calculates

A crossover network splits an audio signal into frequency bands so each speaker driver handles only the range it was designed for. The woofer gets low frequencies through a low-pass filter, and the tweeter gets high frequencies through a high-pass filter. This calculator gives you the exact capacitor and inductor values for first-order (6 dB/octave) and second-order Butterworth (12 dB/octave) passive crossover designs.

## Inputs

- **Crossover Frequency** (Hz) — min 1 — Typical: 80-200 Hz (sub/mid), 2-4 kHz (mid/tweeter).
- **Speaker Impedance** (Ω) — min 1 — Nominal impedance: 4, 8, or 16 ohms.
- **Crossover Order** — options: 1st Order (6 dB/oct), 2nd Order Butterworth (12 dB/oct)

## Outputs

- **High-Pass Capacitor** (μF) — Capacitor in series with the tweeter (high-pass)
- **Low-Pass Inductor** (mH) — Inductor in series with the woofer (low-pass)
- **High-Pass Inductor (2nd order)** (mH) — Shunt inductor for 2nd-order high-pass section
- **Low-Pass Capacitor (2nd order)** (μF) — Shunt capacitor for 2nd-order low-pass section
- **Rolloff Rate** (dB/oct) — How fast the filter attenuates out-of-band signals

## Details

The component values depend on three things: the crossover frequency, the speaker impedance, and the filter order.

First-order crossover (6 dB/octave):

  - High-pass capacitor: C = 1 / (2pifc x Z)

  - Low-pass inductor: L = Z / (2pifc)

  - Uses just one component per driver

  - Gentle slope means drivers overlap significantly near the crossover point

  - Phase-coherent (no phase shift between drivers at crossover)

Second-order Butterworth (12 dB/octave):

  - Steeper rolloff with two components per driver

  - Uses sqrt(2) multiplier for flat amplitude response

  - Introduces 180 degrees of phase shift (reverse tweeter polarity to compensate)

  - Better separation between drivers reduces interference

Common crossover frequency choices:

  - 80-120 Hz: Subwoofer to midrange

  - 200-500 Hz: Woofer to midrange (3-way system)

  - 2000-4000 Hz: Midrange to tweeter

Use non-polarized film capacitors (polypropylene preferred) and air-core or low-DCR inductors for best audio quality. Electrolytic capacitors work in budget builds but add distortion.

## Frequently Asked Questions

**Q: What crossover frequency should I use?**

A: It depends on your drivers. Check the manufacturer specs for each driver's usable frequency range. A good rule: cross over at least an octave away from each driver's resonant frequency and rolloff point. For a typical two-way bookshelf speaker, 2-3 kHz is common. For a subwoofer to satellite system, 80-120 Hz works well.

**Q: Why does speaker impedance matter?**

A: The crossover components form a voltage divider with the speaker impedance. If the impedance changes with frequency (as real speakers do), the actual crossover behavior shifts from the design target. Use the nominal impedance (usually 4 or 8 ohms) as a starting point, and measure the actual impedance at the crossover frequency for a more precise design.

**Q: Should I use first-order or second-order?**

A: First-order crossovers are simpler and maintain phase coherence, making them popular in audiophile designs. However, the gentle 6 dB/octave slope means both drivers play a wide overlapping range, which requires well-behaved drivers. Second-order gives better driver separation and protection but introduces a phase flip (reverse the tweeter polarity). For most DIY builds, second-order Butterworth is a good balance of simplicity and performance.

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Source: https://vastcalc.com/calculators/physics/crossover
Category: Physics
Last updated: 2026-04-08