Passive 3-Way Crossover Calculator (1st Order, 6 dB/oct)
Calculate starting component values for a passive 3-way network with separate woofer, midrange, and tweeter impedances.
Formulas used: L = Z / (2πf), C = 1 / (2πfZ)
What a 3-way crossover does
A 3-way speaker crossover splits audio into three frequency ranges so each driver works where it performs best: the woofer handles bass, the midrange handles vocals and instruments, and the tweeter handles high frequencies. This improves clarity, reduces distortion, and allows higher output compared with a single full-range driver.
How this calculator works
This tool uses first-order passive crossover equations (6 dB/octave slope). You provide each driver's nominal impedance and two crossover points:
- f1 (Low-Mid): where woofer transitions to midrange
- f2 (Mid-High): where midrange transitions to tweeter
The calculator returns:
- Woofer low-pass inductor at f1
- Midrange high-pass capacitor at f1
- Midrange low-pass inductor at f2
- Tweeter high-pass capacitor at f2
Formulas used
Low-pass inductor
L = Z / (2πf)
High-pass capacitor
C = 1 / (2πfZ)
Where Z is driver impedance in ohms and f is crossover frequency in hertz. The calculator displays in practical units: mH for inductors and µF for capacitors.
How to pick frequencies
Good crossover points depend on each driver's frequency response and distortion behavior. As a quick starting point:
- Woofer to midrange: often between 250 Hz and 800 Hz
- Midrange to tweeter: often between 2 kHz and 5 kHz
- Keep the midrange working comfortably between both points
- Use manufacturer response graphs whenever possible
Important real-world notes
1) Nominal impedance is not constant
Speakers are reactive loads. “8 Ω” is only a nominal value, and true impedance changes with frequency. These values are excellent for first-pass design, but measurement and tuning are needed for final accuracy.
2) Driver sensitivity matching
Many designs need an L-pad resistor network to level-match a louder tweeter or midrange. This calculator focuses on crossover frequency components only.
3) Component quality matters
- Use low-DCR inductors for better bass control
- Use film capacitors for mid/tweeter paths when practical
- Choose adequate voltage and power ratings
Example setup
If all drivers are 8 Ω, with crossover points at 500 Hz and 3500 Hz, this calculator produces:
- Woofer inductor: about 2.546 mH
- Mid high-pass capacitor: about 39.789 µF
- Mid low-pass inductor: about 0.364 mH
- Tweeter capacitor: about 5.684 µF
These are starting values. In a final build, you’d normally test and fine-tune by ear and measurement.
Frequently asked questions
Can I use this for car audio?
Yes. The math is the same for passive crossovers, as long as you input the correct nominal impedance and target crossover points.
Can I build with nearest standard values?
Absolutely. Choose the nearest standard capacitor/inductor values, then listen and adjust as needed.
Is first-order always best?
Not always. First-order networks are simple and phase-friendly, but they provide gentler roll-off. Many systems use second-order or higher slopes for better driver protection and reduced overlap.