Free calculator
Passive crossover calculator: 2-way, 1st to 4th order
Enter the crossover frequency, alignment and the drivers' impedance – the calculator gives you the capacitors and inductors for the high-pass (tweeter) and low-pass (woofer), rounded to E12 or E24 if you like.
Inputs and result
High-pass (tweeter)
| Part | Position | Value |
|---|---|---|
| C1 | in series | 3.9 µF |
| L1 | across the driver | 0.33 mH |
| C2 | in series | 8.2 µF |
| L2 | across the driver | 1.5 mH |
Low-pass (woofer)
| Part | Position | Value |
|---|---|---|
| L3 | in series | 1 mH |
| C3 | across the driver | 12 µF |
| L4 | in series | 0.47 mH |
| C4 | across the driver | 2.7 µF |
Connect both drivers with the same polarity.
Formulas
ω = 2π · fc Low-pass: L = l · R / ω C = c / (R · ω) High-pass: C = 1 / (l · R · ω) L = R / (c · ω) Normalised values (amplifier → driver): 1.886 · 1.591 · 0.9428 · 0.3536
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.
Opens a new project with exactly this circuit. Works as a guest without an account; then load your drivers' FRD/ZMA.
Which alignment?
- Butterworth: maximally flat passband, −3 dB at the crossover frequency. In 2nd order the two branches (tweeter inverted) sum to +3 dB around the crossover, in 3rd order flat.
- Linkwitz-Riley: two Butterworth filters in a row, −6 dB at the crossover frequency; the sum is flat. Defined for 2nd and 4th order only – LR4 is the classic 24 dB/oct crossover.
- Bessel: the most even group delay and a gentler transition. Phase-normalised here: at the crossover frequency each branch has half its final phase (−n·45°).
How the calculator works
Every crossover is an LC ladder driven by an amplifier (0 Ω source) into a resistive load R – the driver's nominal impedance. The part values follow from the alignment's normalised table values (for 1 Ω and ω = 1).
In the low-pass the inductors are in series and the capacitors across the driver; in the high-pass it is the other way round. A 3rd-order Butterworth, for example, gives the well-known L₁ = 3R/(4πf), C = 2/(3πfR), L₂ = R/(4πf).
Limits
- Real drivers are not resistors: their impedance rises with the voice coil inductance and peaks at resonance. A crossover for 8 Ω behaves very differently on a tweeter that shows 15 Ω at 2 kHz. A Zobel network or a notch often helps.
- The drivers' acoustic response is not flat. The electrical filter plus the driver's own response makes the acoustic slope – and that decides whether the sum works.
- Inductors have a DC resistance (DCR) that changes level and Q; Crover includes it in the simulation.