Audio Crossover Frequency Calculator

A crossover is a filter network that divides an audio signal into separate frequency bands for different speakers. Without a crossover, a tweeter receiving bass frequencies would be damaged, and a woofer receiving high frequencies would produce distortion.

Why Crossovers Are Necessary

Different speaker drivers are optimized for different frequency ranges:

• Subwoofer: 20–80 Hz (very low bass)
• Woofer: 40–500 Hz (bass and upper bass)
• Midrange: 300 Hz – 5 kHz
• Tweeter: 2 kHz – 20 kHz

A crossover filters each driver so it receives only the frequencies it can handle efficiently.

Crossover Orders

1st Order (6 dB/octave): Single capacitor for high-pass, single inductor for low-pass. Simple, phase coherent. Used in simple 2-way systems.

2nd Order (12 dB/octave): More aggressive filtering with better driver protection. Most common in home audio.

3rd Order (18 dB/octave): Better isolation, used in professional and high-performance systems.

4th Order Linkwitz-Riley (24 dB/octave): Flat summed response, excellent isolation. Common in studio monitors.

This calculator covers the first two of those, which is where nearly all DIY passive crossover work sits. Third and fourth order passive networks need more components, tighter tolerances and real measurement gear to get right, and are usually done actively (before the amplifier) instead.

The Formulas

At crossover frequency f (Hz) into a driver of impedance Z (ohms), writing ω₀ = 2πf:

In the shorthand most speaker-building references use, with f in Hz, Z in ohms, C in µF and L in mH:

• 1st order: C = 159,200 / (f Z), L = 159.2 Z / f
• 2nd Butterworth: C = 112,500 / (f Z), L = 225.1 Z / f
• 2nd Linkwitz-Riley: C = 79,600 / (f Z), L = 318.3 Z / f

Butterworth or Linkwitz-Riley?

Both roll off at 12 dB per octave, and both leave the two drivers 180 degrees apart at the crossover point. Wire them the same way round and they cancel into a deep notch there, so a 2nd-order network always has one driver, usually the tweeter, wired with reversed polarity.
With that done, the two part company. Each Butterworth half is 3 dB down at the crossover and the pair sums to a 3 dB bump. Each Linkwitz-Riley half is 6 dB down and the pair sums flat, which is why Linkwitz-Riley dominates studio monitor design (mostly in its 4th-order form, which sums flat with no polarity flip at all). LR needs a larger inductor and a smaller capacitor for the same frequency, which the table above shows.

Typical Crossover Points

• Subwoofer to woofer: 80–120 Hz
• Woofer to midrange: 400–800 Hz
• Midrange to tweeter: 2,000–5,000 Hz
• Woofer to tweeter (2-way): 2,000–4,000 Hz

Impedance Note

Nominal impedance for home speakers is typically 4, 6, or 8 ohms. Car audio speakers are often 4 ohms. Use the manufacturer’s specified impedance for accurate component calculations.