Free Speaker Crossover Calculator
Calculate passive crossover component values (capacitors in μF and inductors in mH) for 2-way loudspeaker driver integration.
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Passive Speaker Crossover Design Principles
Loudspeakers use specialized drivers: large woofers excel at moving air for bass, while delicate lightweight tweeters reproduce high frequencies. Sending low bass signals into a dome tweeter will physically shatter its voice coil. A passive crossover splits the amplifier signal into separate frequency bands.
Linkwitz-Riley vs Butterworth
Standard 2nd-order Butterworth filters are down 3dB at cutoff, causing a +3dB peak bump in summed acoustic power at the crossover point. The 2nd-order Linkwitz-Riley alignment drops each driver by 6dB at $F_c$, producing a perfectly flat, smooth frequency response across the transition.
The 2nd-Order Inverted Phase Trick
A 2nd-order (12 dB/oct) passive filter inherently shifts phase by 180 degrees at crossover. If you connect both drivers in positive polarity, their sound waves cancel destructively, creating a deep notch. Inverting the tweeter's wiring (+ to -) restores perfect in-phase summation!
Frequently Asked Questions
What capacitor voltage rating do I need for speaker crossovers?
Never use cheap polarized electrolytic capacitors. Always use metallized polypropylene film capacitors rated for at least 100V (preferably 250V or 400V) to handle high amplifier AC voltage peaks without breakdown.
Should I buy air-core or iron-core inductors?
Use air-core inductors for the high-pass tweeter filter and midrange to prevent magnetic core saturation and harmonic distortion. Iron-core or ferrite-core inductors are only used in low-frequency woofer circuits where large inductance (e.g. > 4 mH) would otherwise require huge, expensive spools of copper wire.
How do I choose the best crossover frequency?
Check your tweeter's resonant frequency ($F_s$). As a rule of thumb, set the crossover frequency at least two octaves above $F_s$ (e.g. if a tweeter resonates at 1,000 Hz, cross over at 2,200 Hz or higher) to protect the diaphragm from over-excursion.