Free calculator
3-way crossover calculator: passive, 1st to 4th order
Enter two crossover frequencies, the alignment and the impedance of the three drivers – the calculator gives you the inductors and capacitors for the low-pass, the midrange's band-pass and the high-pass, rounded to E12 or E24 if you like.
Inputs and result
High-pass (tweeter)
| Part | Position | Value |
|---|---|---|
| C1 | in series | 3.3 µF |
| L1 | across the driver | 0.27 mH |
| C2 | in series | 6.8 µF |
| L2 | across the driver | 1.2 mH |
Band-pass (midrange): high-pass first, then low-pass
| Part | Position | Value |
|---|---|---|
| C3 | in series | 27 µF |
| L3 | across the driver | 2.2 mH |
| C4 | in series | 56 µF |
| L4 | across the driver | 8.2 mH |
| L5 | in series | 0.82 mH |
| C5 | across the driver | 10 µF |
| L6 | in series | 0.39 mH |
| C6 | across the driver | 2.2 µF |
Low-pass (woofer)
| Part | Position | Value |
|---|---|---|
| L7 | in series | 5.6 mH |
| C7 | across the driver | 82 µF |
| L8 | in series | 3.3 mH |
| C8 | across the driver | 18 µF |
Connect all three drivers with the same polarity.
The formulas assume a resistive load. Real drivers have an impedance that rises with frequency and peaks at resonance, and a response of their own – so the crossover behaves differently from the calculation. Only a simulation with measured FRD and ZMA data shows how it will sound.
In Crover you draw the crossover with these values and simulate it with your drivers' measurements.
How the calculator works
Every edge is an LC ladder into the driver's nominal impedance, exactly as on the 2-way calculator: the woofer gets the low-pass of the lower crossover, the tweeter the high-pass of the upper one.
The midrange gets both: first the high-pass of the lower crossover, then the low-pass of the upper one. Both sections are calculated for the midrange's impedance – the textbook method, and accurate as long as the crossovers are far enough apart.
Limits
- Real drivers are not resistors, and a midrange often has its resonance right at the crossover to the woofer. Without measurements (FRD/ZMA) every crossover is only a starting point.
- Three drivers only sum flat when their timing fits too – the midrange usually sits elsewhere on the baffle than the woofer and the tweeter.
- Inductors have a DC resistance (DCR); in the band-pass the low-pass coil sits in series with the midrange and lowers its level.