       # Car Audio / Passive Crossovers, Narrow Band Pass Calculator

Use these formulas to calculate values for Narrow Band Pass filters only! These are completely different formulas than the ones used here, and should only be used when the low pass frequency is less than 20 times the high pass frequency. Remember, the low pass frequency (F2) is higher than the high pass frequency (F1).

Before clicking for the crossover component values, enter the net impedance level and the desired crossover frequencies. Values should be rounded off to the nearest hundredth.

If you need a 16 mHy coil, you can series a 12.8 mHy coil and a 3.2 mHy coil. If you need a 70 µfd capacitor, you can parallel two 35 µfd capacitors.When the exact value of a coil or capacitor is not available, you can substitute values of ± 5%.

Crossover Calculators:
High Pass/Low Pass Calculator
Narrow Band Pass Calculator
Zobel Calculator

## Passive Crossover Narrow Band Pass Filter Capacitor and Coil Calculator Narrow Band Pass Filter Calculator
 Net Impedance High Pass Frequency Low Pass Frequency Ohms Hertz (Hz) Hertz (Hz)
1st Order (6 dB per Octave) Narrow Band Pass (diagram)
Formulas for first order only, calculate for L1 first, then C1.
L1 = Net Impedance / [(F2 - F1) x 6.283] x 1,000 = L1 in (mHy) Coil - L1 Millihenries (mHy)
C1 = 1 / (39.472 x [L1/1000] x [F1 x F2]) x 1,000,000 = C1 in (µfd) Capacitor - C1 Microfarads (µfd)
2nd Order (12 dB per Octave) Narrow Band Pass (diagram)
Formulas for second order only, calculate for C1 first, then L2, C2, L1.
L1 = 1 / (39.472 x C1 x [F1 x F2]) x 1,000 = L1 in (mHy) Coil - L1 Millihenries (mHy)
C1 = .707 / (Net Impedance x 6.283 x [F2 - F1]) x 1,000,000 = C1 in (µfd) Capacitor - C1 Microfarads (µfd)
L2 = 1 / (C1 x [6.283 x (F2 - F1)]2) x 1,000 = L2 in (mHy) Coil - L2 Millihenries (mHy)
C2 = 1 / (39.472 x L2 x [F1 x F2]) x 1,000,000 = C2 in (µfd) Capacitor - C2 Microfarads (µfd)
3rd Order (18 dB per Octave) Narrow Band Pass (diagram)
Formulas for third order only, calaculate for L3 first, then C2, C3, L2, L1, C1.
L1 = 1 / (.499849 x [6.283 x (F2 - F1)]2 x C2) x 1,000 = L1 in (mHy) Coil - L1 Millihenries (mHy)
C1 = 1 / (39.472 x [F1 x F2] x L1) x 1,000,000 = C1 in (µfd) Capacitor - C1 Microfarads (µfd)
L2 = 1 / (39.472 x [F1 x F2] x C2) x 1,000 = L2 in (mHy) Coil - L2 Millihenries (mHy)
C2 = 1 / (1.4884 x [6.283 x (F1 - F2)]2 x L3 x 1,000,000 = C2 in (µfd) Capacitor - C2 Microfarads (µfd)
L3 = (.5 x Net Impedance) / (6.283 x [F2 - F1]) x 1,000 = L3 in (mHy) Coil - L3 Millihenries (mHy)
C3 = 1 / (39.472 x [F1 x F2] x L3) x 1,000,000 = C3 in (µfd) Capacitor - C3 Microfarads (µfd) •
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