Audio Crossover Calculator

Design passive speaker filters with precision. Calculate capacitor and inductor values for your 2-way audio crossover networks.

Component Values

Formula Explanation: These values are for a passive crossover. The high-pass filter (for the tweeter) uses a capacitor in series, and the low-pass filter (for the woofer) uses an inductor in series. A 2nd order filter adds a component in parallel for a steeper cutoff.

Visual representation of the selected filter slope.

What is an Audio Crossover Calculator?

An audio crossover calculator is an essential tool for designing speaker systems. It helps you determine the correct component values (capacitors and inductors) needed to build a passive crossover circuit. A crossover’s job is to split a full-range audio signal from an amplifier into separate frequency bands, sending high frequencies to the tweeter and low frequencies to the woofer. This ensures each speaker driver only receives the frequencies it’s designed to reproduce, preventing damage and resulting in a much clearer, more balanced sound.

This calculator is specifically a 2-way audio crossover calculator, ideal for systems with one woofer and one tweeter. Without a crossover, a tweeter would try to reproduce low bass notes, which could quickly destroy it, and a woofer’s attempt to reproduce high frequencies would sound muddy. Therefore, using a crossover is fundamental to proper hi-fi speaker design. For more on the basic components, see our guide to a {related_keywords}.

Audio Crossover Formula and Explanation

The calculations for passive crossovers are based on the desired crossover frequency and the speaker’s impedance. The formulas change depending on the ‘order’ of the crossover, which determines how sharply it filters the frequencies (its “slope”).

1st Order Butterworth Filter (6 dB/octave slope)

• High-Pass (for Tweeter): C = 1 / (2 * π * f * R)
• Low-Pass (for Woofer): L = R / (2 * π * f)

2nd Order Linkwitz-Riley Filter (12 dB/octave slope)

• High-Pass (for Tweeter): C = 1 / (2 * π * f * R), L = R / (2 * π * f)
• Low-Pass (for Woofer): L = R / (2 * π * f), C = 1 / (2 * π * f)

Crossover Formula Variables

Variable	Meaning	Unit (auto-inferred)	Typical Range
C	Capacitance	Microfarads (µF)	1 – 100 µF
L	Inductance	Millihenries (mH)	0.1 – 5.0 mH
R	Speaker Impedance	Ohms (Ω)	4, 6, 8 Ω
f	Crossover Frequency	Hertz (Hz)	500 – 5000 Hz
π	Pi	Constant	~3.14159

Building a full speaker system? You might also need a {related_keywords}.

Practical Examples

Example 1: 2-Way Bookshelf Speaker

You’re building a pair of bookshelf speakers with an 8 Ohm woofer and an 8 Ohm tweeter. You want to cross them over at 2,200 Hz using a 2nd order Linkwitz-Riley filter for a good phase response between the drivers.

• Inputs: Crossover Type = 2nd Order LR, Speaker Impedance = 8 Ω, Crossover Frequency = 2200 Hz.
• High-Pass Results (Tweeter): The calculator would show a Capacitor (C) of 9.04 µF and an Inductor (L) of 0.58 mH.
• Low-Pass Results (Woofer): The calculator would show an Inductor (L) of 0.58 mH and a Capacitor (C) of 9.04 µF.

Example 2: Simple Subwoofer Low-Pass Filter

You have a car audio subwoofer with a 4 Ohm impedance and you want to prevent it from playing any mid-range frequencies. You decide to use a simple 1st order low-pass filter at 100 Hz.

• Inputs: Crossover Type = 1st Order Low-Pass, Speaker Impedance = 4 Ω, Crossover Frequency = 100 Hz.
• Results: The audio crossover calculator would recommend one component: an Inductor (L) of 6.37 mH. The capacitor is not used in this simple filter.

How to Use This Audio Crossover Calculator

1. Select Crossover Type: Choose the filter order and type. A “2nd Order Linkwitz-Riley” is a very popular and effective choice for standard 2-way speakers. A “1st Order” filter is simpler but has a more gradual cutoff.
2. Enter Speaker Impedance: Input the nominal impedance of your speaker driver, which is usually printed on the magnet or in its specifications (typically 4, 6, or 8 Ohms).
3. Enter Crossover Frequency: Decide on the frequency where you want to divide the sound. For a typical 6.5-inch woofer and 1-inch tweeter, a frequency between 2000 Hz and 3000 Hz is common.
4. Interpret the Results: The calculator will instantly provide the required values for the capacitor (in microfarads, µF) and the inductor (in millihenries, mH). The circuit diagram will depend on whether you are building the high-pass (for the tweeter) or low-pass (for the woofer) section. Understanding impedance is key, learn more about {related_keywords}.

Key Factors That Affect Crossover Design

• Driver Frequency Response: The natural range of your woofer and tweeter determines the ideal crossover point. You can’t force a driver to play frequencies it’s not capable of.
• Impedance Curve: A speaker’s impedance is not a flat line; it varies with frequency. Our calculator uses the nominal impedance, but advanced designs compensate for these variations.
• Phase Alignment: Different filter orders introduce different amounts of phase shift. 2nd order Linkwitz-Riley filters are popular because the woofer and tweeter remain in phase at the crossover point.
• Component Tolerance: Capacitors and inductors have a tolerance (e.g., ±5%). Using high-quality components with tight tolerances ensures your crossover performs as designed.
• Power Handling: The components must be able to handle the power from your amplifier. Inductors should have low DC resistance (DCR), and capacitors should have an adequate voltage rating.
• Driver Sensitivity (SPL): If your tweeter is more efficient (louder) than your woofer, you may need an L-Pad circuit in addition to the crossover to balance the volume levels. Check out our guide on {related_keywords} for more tips.

Frequently Asked Questions (FAQ)

1. What’s the difference between a 1st and 2nd order crossover?

A 1st order crossover has a gentler slope of 6 dB per octave, while a 2nd order has a steeper 12 dB per octave slope. The steeper slope provides better protection for the tweeter and less frequency overlap between drivers.

2. Why are the units in microfarads (µF) and millihenries (mH)?

These are the standard, practical units for crossover components. The base formulas produce values in Farads and Henries, which are then multiplied (by 1,000,000 for µF and 1,000 for mH) to get values that are easier to find and purchase.

3. Do I use the same components for the woofer and tweeter?

No. For a 2nd order filter, you will build two separate circuits. The high-pass filter for the tweeter uses a capacitor and inductor, and the low-pass filter for the woofer uses its own inductor and capacitor, wired differently.

4. What is a Linkwitz-Riley vs. a Butterworth filter?

They are two different filter alignments. Both are 12dB/octave for a 2nd order. Linkwitz-Riley filters sum to a flat frequency response at the crossover point and keep the drivers in phase, making them a top choice for 2-way speaker design.

5. Can I use a value close to the calculated one?

Yes. It is often impossible to find the exact component value. It is standard practice to use the closest commercially available value, typically within 5-10% of the calculated target. Our {related_keywords} can help with this.

6. Do I need one audio crossover calculator per speaker?

You use the calculator to get the design (the component values). You then need to buy and assemble a set of those components for each speaker cabinet you are building.

7. What if my tweeter and woofer have different impedances?

This calculator assumes both drivers have the same impedance. For mixed impedances, you would need to calculate the high-pass and low-pass sections separately by running the calculator twice with the respective impedance values.

8. Is a passive crossover better than an active one?

Passive crossovers are simpler and don’t require external power. Active crossovers are more complex and require bi-amping (separate amplifier channels for woofer and tweeter) but offer greater control and precision. This calculator is for passive crossovers.