Crossover calculator for 2-way and 3-way speakers
A passive crossover splits the amplifier’s signal so each driver gets only the frequencies it handles well: bass to the woofer, treble to the tweeter. This crossover calculator gives the capacitor and inductor values for 2-way and 3-way networks with Butterworth or Linkwitz-Riley alignments from 1st to 4th order, plus L-pad resistors to bring a louder tweeter or midrange down to match the woofer.
It also simulates the network and plots each driver’s output and the sum, so you can see the effect of polarity, order and spacing before you buy parts. Everything is calculated in your browser.
How to use the Crossover Calculator
- Choose 2-way or 3-way, then the alignment and the order (slope).
- Enter the crossover frequency (two frequencies for 3-way) and each driver’s impedance.
- If the tweeter or midrange is more sensitive than the woofer, enter the difference in dB as its L-pad.
- Read the parts list, check the plot, and copy the values for your parts order.
Crossover Calculator features
Six alignments
1st order, Butterworth 2nd–4th order and Linkwitz-Riley 2nd and 4th order.
2-way and 3-way
Woofer, midrange band-pass and tweeter sections with separate impedances.
L-pad resistors
Series and parallel resistor values that cut the level without changing the load the filter sees.
Polarity advice
Recommended driver polarity for each order, with your own override.
Response plot
A circuit simulation of every section and the acoustic sum for ideal drivers.
How the values are calculated
For a low-pass section the inductors are L = k × R ÷ f and capacitors C = k ÷ (R × f), with R the driver impedance and f the crossover frequency; high-pass sections swap the parts. The constants k come from the normalised filter tables. This tool derives them from each filter’s polynomial for a network fed from an amplifier into a resistive load, and they agree with the widely published tables (for example LR2: 0.3183 and 0.0796; LR4 high-pass: 0.0844, 0.1000, 0.1688, 0.4502).
Example: a 2-way Linkwitz-Riley 2nd-order crossover at 2,500 Hz with 8 Ω drivers needs a 1.02 mH inductor in series and a 3.98 µF capacitor across the woofer, and a 3.98 µF capacitor in series with a 1.02 mH inductor across the tweeter, which is wired in reverse polarity.
| Alignment | Level at fc | Polarity for a flat sum |
|---|---|---|
| 1st order | −3 dB | normal |
| Butterworth 2nd | −3 dB | reversed tweeter (+3 dB bump) |
| Linkwitz-Riley 2nd | −6 dB | reversed tweeter (flat) |
| Butterworth 3rd | −3 dB | either (flat) |
| Butterworth 4th | −3 dB | normal (+3 dB bump) |
| Linkwitz-Riley 4th | −6 dB | normal (flat) |
L-pads
An L-pad is two resistors: R1 = Z(1 − 10^(−A/20)) in series and R2 = Z × 10^(−A/20) ÷ (1 − 10^(−A/20)) across the driver, for A dB of cut on a Z-ohm driver. The pair still looks like Z ohms to the crossover, so the filter frequency does not move. For 6 dB on an 8 Ω tweeter that is 3.99 Ω and 8.04 Ω; use the nearest standard values and resistors rated for a few watts.
3-way crossovers and real drivers
- In a 3-way network the midrange high-pass and low-pass sections load each other. Keep them at least 3 octaves apart (for example 500 Hz and 4 kHz); closer spacing shows up as a bump or dip in the plot. Published 3-way tables (Bullock, JAES 1983–85) adjust the midrange values for 8:1 and 10:1 spreads; this tool uses independent sections and shows you the result instead.
- A driver’s impedance rises with frequency because of its voice-coil inductance, so a filter designed for a fixed 8 Ω can drift. A Zobel network (a resistor and capacitor across the driver) flattens it.
- Different driver sensitivities and acoustic offsets change the summed response. Measure, then fine-tune with an L-pad or in a simulator.
- Use film capacitors in the tweeter path and air-core or low-resistance inductors for the woofer; check each part’s tolerance.
Crossover Calculator FAQ
How do I calculate a 2-way crossover?
Choose the alignment and order, enter the crossover frequency and each driver’s impedance, and this crossover calculator gives every capacitor and inductor. For a first build, Linkwitz-Riley 2nd order at the frequency the tweeter maker recommends is a good starting point.
Which is better, Butterworth or Linkwitz-Riley?
Linkwitz-Riley sections are each −6 dB at the crossover point, so the woofer and tweeter add up flat. Butterworth sections are −3 dB, which leaves a 3 dB bump in 2nd and 4th order.
Why is the tweeter wired backwards in a 2nd-order crossover?
A 2nd-order low-pass and high-pass are 180° apart at the crossover frequency. Reversing the tweeter brings them back in phase so they add instead of cancelling.
What does an L-pad do?
It reduces a driver’s level by a fixed number of dB while keeping the impedance the crossover sees the same.
What frequency should I cross over at?
Stay above the tweeter’s resonance (often 2–3 times it) and below the frequency where the woofer starts to beam or break up. Many 2-way speakers cross between 1.8 and 3.5 kHz.
Can I use this for a car audio or subwoofer crossover?
Yes, the maths is the same for 4 Ω or 2 Ω car drivers and for a low-pass on a passive subwoofer, but large inductors for low frequencies get expensive and lossy; an active crossover is often better below about 200 Hz.