2-way crossover designer
Tweeter · high-pass
High-pass section
| Part | Position | Calculated | Nearest E12 | Deviation |
|---|
Woofer · low-pass
Low-pass section
| Part | Position | Calculated | Nearest E12 | Deviation |
|---|
3-way crossover designer
Woofer · low-pass
Low-pass section
| Part | Position | Calculated | Nearest E12 | Deviation |
|---|
Midrange · band-pass
Band-pass: high-pass + low-pass
The midrange driver gets both halves in series: the high-pass parts block bass, the low-pass parts block treble.
| Part | Position | Calculated | Nearest E12 | Deviation |
|---|
Tweeter · high-pass
High-pass section
| Part | Position | Calculated | Nearest E12 | Deviation |
|---|
Reference, examples & FAQ
Worked examples
Example 1 — classic 2-way bookshelf: 3,000 Hz, 8 Ω, 12 dB/oct Butterworth
ω = 2π × 3,000 = 18,849.6 rad/s. Tweeter high-pass: C1 = 0.7071 ÷ (8 × 18,849.6) = 4.69 µF (→ E12 4.7 µF), L1 = 1.4142 × 8 ÷ 18,849.6 = 0.600 mH (→ E12 0.56 mH). Woofer low-pass: L1 = 0.600 mH, C1 = 4.69 µF — the same two values, mirrored. Reverse the tweeter polarity (12 dB/oct = 180° phase shift).
Example 2 — 3-way midrange band-pass: 800 Hz / 4,500 Hz, 8 Ω, 12 dB/oct Linkwitz-Riley
High-pass half at 800 Hz: C1 = 0.5 ÷ (8 × 5,026.5) = 12.43 µF, L1 = 2 × 8 ÷ 5,026.5 = 3.183 mH. Low-pass half at 4,500 Hz: L1 = 2 × 8 ÷ 28,274.3 = 0.566 mH, C1 = 0.5 ÷ (8 × 28,274.3) = 2.210 µF. Wire all four parts in series with the mid driver, in the order shown in the 3-Way tab schematic.
Example 3 — 4 Ω car audio: 3,500 Hz, 4 Ω, 12 dB/oct Butterworth
Halve the impedance → inductors halve, capacitors double vs the 8 Ω design. Tweeter: C1 = 0.7071 ÷ (4 × 21,991.1) = 8.04 µF, L1 = 1.4142 × 4 ÷ 21,991.1 = 0.257 mH. Woofer: L1 = 0.257 mH, C1 = 8.04 µF.
Formula reference (w = 2π·fc, R = driver impedance)
| Slope | Alignment | Low-pass (series → shunt) | High-pass (series → shunt) | @ fc |
|---|---|---|---|---|
| 6 dB/oct | — | L1 = R/w | C1 = 1/(R·w) | −3.0 dB |
| 12 dB/oct | Butterworth | L1 = 1.4142·R/w, C1 = 0.7071/(R·w) | C1 = 0.7071/(R·w), L1 = 1.4142·R/w | −3.0 dB |
| 12 dB/oct | Linkwitz-Riley | L1 = 2·R/w, C1 = 0.5/(R·w) | C1 = 0.5/(R·w), L1 = 2·R/w | −6.0 dB |
| 18 dB/oct | Butterworth | L1 = 1.5·R/w, C1 = 1.3333/(R·w), L2 = 0.5·R/w | C1 = 0.6667/(R·w), L1 = 0.75·R/w, C2 = 2/(R·w) | −3.0 dB |
| 24 dB/oct | Butterworth | L1 = 1.5307·R/w, C1 = 1.5774/(R·w), L2 = 1.0824·R/w, C2 = 0.3827/(R·w) | C1 = 0.6533/(R·w), L1 = 0.6340·R/w, C2 = 0.9239/(R·w), L2 = 2.6131·R/w | −3.0 dB |
| 24 dB/oct | Linkwitz-Riley | L1 = 1.8856·R/w, C1 = 1.5912/(R·w), L2 = 0.9428·R/w, C2 = 0.3536/(R·w) | C1 = 0.5303/(R·w), L1 = 0.6284·R/w, C2 = 1.0607/(R·w), L2 = 2.8284·R/w | −6.0 dB |
Methodology & scope boundaries
Filter math. Each section is a constant-impedance LC ladder driven by a ~0 Ω source (a typical solid-state amplifier) into the driver's nominal impedance R. Low-pass ladders run series-L / shunt-C; high-pass ladders are the exact LP↔HP dual (series Ci = 1/(w²·Li), shunt Li = 1/(w²·Ci)). Normalized element values come from the Butterworth and Linkwitz-Riley transfer-function denominators and were verified numerically: Butterworth sections measure exactly −3.0103 dB at fc, Linkwitz-Riley exactly −6.0206 dB, with asymptotic slopes of 6/12/18/24 dB per octave.
Nearest standard parts. E12 deviations are computed in log space across all decades; a 5% part error shifts the crossover point by only ~2–3%.
Assumptions & limits. Real drivers are not flat resistors: impedance peaks at resonance (Fs) and rises with voice-coil inductance, which moves the true crossover point away from the textbook value. For critical builds, flatten the impedance with a Zobel network and measure the result. This tool designs passive crossovers (capacitors + inductors at speaker level) — it does not design active/DSP crossovers.
Boundaries (anti-cannibal). This tool covers passive speaker crossover part values only. It does not duplicate generic electronics calculators elsewhere in the directory.
Safety. Double-check tweeter polarity (reverse for 12 dB/oct) and capacitor voltage ratings (≥100 V) before powering up. Start listening tests at low volume.
Privacy. 100% client-side — no server, no tracking, no data leaves your browser.
Frequently asked questions
What is a speaker crossover calculator?
A speaker crossover calculator computes the capacitor (µF) and inductor (mH) values for a passive crossover network — the circuit that splits an audio signal so the tweeter only gets high frequencies and the woofer only gets low frequencies. You enter the crossover frequency, the driver impedance (e.g. 8 ohm), and the filter slope (6, 12, 18 or 24 dB/octave); the calculator returns every part value for 2-way and 3-way designs, plus the nearest standard E12 part values you can actually buy.
How do I calculate capacitor and inductor values for a crossover?
Use the normalized formulas with w = 2π × crossover frequency and R = driver impedance. First order (6 dB/oct): L = R/w for the low-pass, C = 1/(R×w) for the high-pass. Second order Butterworth (12 dB/oct): LP uses L1 = 1.4142×R/w with C1 = 0.7071/(R×w); HP uses C1 = 0.7071/(R×w) with L1 = 1.4142×R/w. Higher orders add more sections — the calculator above applies the exact Butterworth and Linkwitz-Riley polynomials for 18 and 24 dB/oct, verified to hit exactly -3.01 dB (Butterworth) or -6.02 dB (Linkwitz-Riley) at the crossover frequency.
What is the difference between a 2-way and a 3-way crossover?
A 2-way crossover splits the signal once: a low-pass section feeds the woofer and a high-pass section feeds the tweeter, meeting at one crossover frequency (e.g. 3,000 Hz). A 3-way crossover uses two crossover frequencies: the woofer gets a low-pass at the low point (e.g. 800 Hz), the tweeter gets a high-pass at the high point (e.g. 4,500 Hz), and the midrange driver gets a band-pass — a high-pass at 800 Hz cascaded with a low-pass at 4,500 Hz — so it only plays the middle band. Use the 3-Way tab above for the full midrange parts list.
Which crossover slope should I choose: 6, 12, 18 or 24 dB/octave?
Steeper is not automatically better — it is a tradeoff. 6 dB/oct (first order) uses one part per driver and keeps phase simple, but drivers play far outside their comfort zone. 12 dB/oct (second order) is the classic DIY choice: good protection with only two parts per section, but you must reverse the tweeter polarity. 18 dB/oct gives stronger isolation with three parts. 24 dB/oct (fourth order, usually Linkwitz-Riley) gives the sharpest separation and sums flat, at the cost of four parts per section and the most sensitivity to real-world impedance wiggles.
What is the difference between Butterworth and Linkwitz-Riley crossovers?
Both are 12 or 24 dB/oct filter alignments with different behavior at the crossover point. A Butterworth crossover is -3 dB at the crossover frequency, so the summed acoustic output has a +3 dB bump there (in the ideal model). A Linkwitz-Riley crossover is -6 dB at the crossover frequency, so the two drivers sum perfectly flat, and both drivers are always in phase — which is why Linkwitz-Riley is the default for 24 dB/oct designs. Linkwitz-Riley only exists for even orders (12 and 24 dB/oct); odd orders like 18 dB/oct are Butterworth.
What crossover frequency should I use for my speakers?
Follow the drivers, not a rule of thumb: cross the tweeter at least one octave above its resonant frequency (Fs) — a tweeter with Fs = 1,500 Hz is typically crossed at 3,000 Hz or higher with a 12 dB/oct slope. Cross the woofer before it starts beaming or breaking up, commonly 2,000-3,500 Hz for 2-way bookshelf designs. For 3-way systems, typical points are 300-800 Hz (woofer to mid) and 3,000-5,000 Hz (mid to tweeter). When in doubt, check the driver manufacturer's recommended crossover range on its datasheet.
Do I need to reverse the tweeter polarity when building a crossover?
Only for 12 dB/oct (second order) crossovers: they shift phase 180° at the crossover point, so the tweeter must be wired with reversed polarity or the two drivers cancel instead of adding. For 6 dB/oct (90° shift), 18 dB/oct (270° ≡ -90°), and 24 dB/oct (a full 360°, back in phase), keep normal polarity. The calculator shows a polarity verdict automatically for the slope you select.
How does speaker impedance (4 ohm vs 8 ohm) change the crossover calculation?
Inductor values scale directly with impedance and capacitor values scale inversely: halving the impedance from 8 to 4 ohm halves every inductor value and doubles every capacitor value for the same crossover frequency and slope. Always use the driver's nominal impedance (usually 4 or 8 ohm) as printed on the datasheet. Note this is an approximation — a real driver's impedance rises near resonance and with voice-coil inductance — which is why the guide below discusses Zobel networks for critical designs.
Can I use standard E12 capacitor and inductor values instead of the exact calculated ones?
Yes — that is what everyone does, and small deviations barely move the crossover point. A 5% part-value error shifts the crossover frequency by only about 2-3%. The calculator lists the nearest E12 standard value for every part with its percentage deviation, so you can shop directly: for example a calculated 4.69 µF capacitor becomes a standard 4.7 µF part (+0.2%). Avoid stacking errors in the same direction across all parts of one section.
What is a band-pass filter in a 3-way crossover?
The midrange driver in a 3-way system needs a band-pass filter: it must block bass (which would over-excurse the small mid cone) and block treble (which belongs to the tweeter). It is built by cascading a high-pass section tuned to the low crossover frequency with a low-pass section tuned to the high crossover frequency. The 3-Way tab above computes both halves and lists them as one midrange parts list — e.g. for 800 Hz / 4,500 Hz points you get the 800 Hz high-pass parts plus the 4,500 Hz low-pass parts in series with the mid driver.
Why do crossover calculators assume a flat 8 ohm impedance? My driver's impedance curve is not flat.
Because the textbook formulas need a single resistance value, and the nominal impedance (4/8/16 ohm) is the practical stand-in. In reality a driver's impedance peaks at its resonant frequency and climbs at high frequencies from voice-coil inductance, which shifts the real crossover point. For non-critical builds the error is acceptable; for accurate designs, add a Zobel network (a resistor + capacitor in parallel with the driver) to flatten the rising impedance, and consider measuring the driver. Treat calculator values as the correct starting point, not the final word.
Is a steeper crossover slope always better for sound quality?
No. Steeper slopes (18/24 dB/oct) protect drivers better and reduce overlap, but each extra reactive part adds phase rotation, cost, and sensitivity to the driver's real (non-flat) impedance — a 24 dB/oct network built on textbook values can deviate more in practice than a simple 12 dB/oct one. Many respected commercial speakers use 12 dB/oct Linkwitz-Riley or even 6 dB/oct first-order networks. Choose the shallowest slope that keeps each driver inside its comfortable operating range.
Can I use this calculator for car audio crossovers?
Yes for passive in-car networks (the small crossover boxes that come with component speaker sets): the math is identical — enter the speaker impedance (usually 4 ohm) and your target frequency. Most car component sets use 12 dB/oct at around 3,000-4,000 Hz. If your amplifier or head unit has a built-in active/electronic crossover, use that instead: active crossovers filter the signal before amplification, avoid power loss in coils, and this passive-parts calculator does not apply to them.
What is the difference between a passive and an active crossover?
A passive crossover (what this calculator designs) sits between the amplifier and the drivers and is built from capacitors and inductors handling full speaker-level power. An active (electronic) crossover sits before the amplifiers, filters line-level signals with op-amps or DSP, and needs one amplifier channel per driver. Active is more flexible and efficient; passive is simpler, needs no extra amps or power supply, and is the standard for DIY speaker builds and commercial hi-fi speakers.
What parts do I need besides capacitors and inductors to build the crossover?
Beyond the calculated capacitors and inductors: non-polarized capacitors rated for at least 100 V (polypropylene/MKP is the audiophile standard; avoid polarized electrolytics in the signal path), air-core inductors for low distortion (iron-core is acceptable for large-value woofer coils), an L-pad (two resistors) if the tweeter is more efficient than the woofer and needs attenuation, plus a board or terminal cups, hookup wire, and solder. Keep coils at right angles to each other on the board to avoid magnetic coupling.
Is this crossover calculator private? Does my data leave my browser?
Yes, it is fully private: every calculation runs locally in your browser with JavaScript — no server, no tracking, no data ever leaves your device. You can disconnect from the internet and it still works.