Design a passive speaker crossover in seconds. Enter each driver's impedance and the crossover frequency to get every capacitor and inductor value for 1st to 4th order Butterworth and Linkwitz-Riley 2-way or 3-way networks, with wiring positions, driver polarity, the nearest standard part values and a response chart.
Last updated:
Crossover type
Driver impedance
Ω
Nominal rating, or better: measured at the crossover frequency.
Ω
Ω
Crossover frequency
Hz
Hz
Hz
Enter your values to see the result.
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How to use the Speaker Crossover Calculator
Choose 2-way or 3-way and pick the filter order (slope) and alignment.
Enter the impedance of each driver, ideally measured near the crossover frequency.
Enter the crossover frequency (or the low and high points for a 3-way).
Read the parts for each section and where each one is wired, plus the driver polarity.
Download the parts list and use the nearest standard values when buying components.
Crossover formulas
Every passive crossover section here is a ladder of inductors (L) and capacitors (C) driven by the amplifier and loaded by the driver. Each part's value comes from a normalized coefficient g for the chosen alignment, the driver impedance R (ohms) and the crossover frequency f (hertz):
L = (g ÷ 2π) × R ÷ f · C = (g ÷ 2π) ÷ (R × f)
For the high-pass (tweeter) side the positions of L and C swap and the reciprocal 1/g is used. The 1st-order case reduces to the familiar C = 1 ÷ (2πfR) and L = R ÷ (2πf).
Alignment
Slope
Level at fc
Low-pass L1 / C1 / L2 / C2 coefficient
Polarity
1st-order Butterworth
6 dB/oct
−3 dB
0.1592
Normal
2nd-order Butterworth
12 dB/oct
−3 dB
0.2251 / 0.1125
Tweeter reversed
2nd-order Linkwitz-Riley
12 dB/oct
−6 dB
0.3183 / 0.0796
Tweeter reversed
3rd-order Butterworth
18 dB/oct
−3 dB
0.2387 / 0.2122 / 0.0796
Either
4th-order Butterworth
24 dB/oct
−3 dB
0.2436 / 0.2510 / 0.1723 / 0.0609
Normal
4th-order Linkwitz-Riley
24 dB/oct
−6 dB
0.3001 / 0.2532 / 0.1501 / 0.0563
Normal
Example: a 2nd-order Linkwitz-Riley crossover at 2,500 Hz for 8 Ω drivers needs a woofer inductor of 0.3183 × 8 ÷ 2,500 = 1.02 mH and a shunt capacitor of 0.0796 ÷ (8 × 2,500) = 3.98 µF. The tweeter gets a 3.98 µF series capacitor and a 1.02 mH shunt inductor, wired in reverse polarity.
Tips for building a passive crossover
Measure first: driver impedance is not flat. Use an impedance plot or a Zobel network (a resistor and capacitor across the woofer) so the low-pass sees something close to a resistor.
Level-match the tweeter: tweeters are usually more sensitive than woofers. An L-pad (two resistors) after the high-pass network lowers its level without changing the crossover point much, as long as the network sees the same impedance.
Keep inductors apart: mount coils at right angles to each other and away from steel to avoid coupling and saturation.
Pick sensible crossover points: keep the tweeter well above its resonance (often 2× its Fs or more) and the woofer below the frequency where it starts to beam or break up.
Tolerance: parts within about 5% of the calculated value are fine. Parallel capacitors add (C = C1 + C2); series inductors add (L = L1 + L2) if they are not coupled.
Frequently asked questions
How do I calculate a crossover capacitor value?
For a 1st-order high-pass filter the capacitor is C = 1 ÷ (2π × f × R). For an 8 Ω tweeter crossed at 3,000 Hz that is 1 ÷ (2π × 3,000 × 8) = 6.63 µF. Higher-order filters use the same idea with different coefficients for each part, which this calculator applies automatically.
What is the difference between Butterworth and Linkwitz-Riley crossovers?
Both are standard filter alignments. A Butterworth section is 3 dB down at the crossover frequency, so a 2nd- or 4th-order Butterworth pair sums to a 3 dB bump there. A Linkwitz-Riley section is 6 dB down at the crossover point, so the woofer and tweeter add up to a flat response, which is why LR2 and LR4 are popular for speakers.
Why is the tweeter wired in reverse polarity?
In a 2nd-order crossover the low-pass and high-pass outputs are 180 degrees apart at the crossover frequency. Without flipping one driver they cancel and leave a deep notch. Reversing the tweeter (or the midrange in a 3-way) brings them back in phase. 1st- and 4th-order designs use normal polarity.
Which crossover order should I use?
1st order (6 dB/octave) uses one part per driver but lets the tweeter receive a lot of low-frequency energy. 2nd order (12 dB/octave) is the common choice for home and car 2-ways. 3rd and 4th order (18 and 24 dB/octave) protect the drivers better and narrow the overlap region but need more parts and closer matching.
Should I use the nominal or measured impedance?
The formulas assume a resistive load. A driver rated 8 Ω often measures 10 Ω or more at a few kHz because of voice-coil inductance. Using the impedance measured at the crossover frequency, or adding a Zobel network to flatten it, gives results much closer to the textbook response.
What kind of capacitors and inductors should I buy?
Use non-polarized film capacitors (polypropylene is common) and air-core inductors in the signal path to avoid distortion. Pick the nearest standard value; being within about 5 percent of the calculated value is fine for most builds, and capacitors can be paralleled to reach a value.
How far apart should the crossover points of a 3-way be?
Simple 3-way networks work best when the low and high crossover points are about 2 to 3 octaves or more apart, for example 400 Hz and 3,500 Hz. When they are closer, the midrange high-pass and low-pass sections interact and the midrange response sags.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.