Speaker Crossover Frequency Calculator
Finds the optimal crossover frequency for a two-way speaker system using the geometric mean of the woofer's upper limit and the tweeter's lower limit. Used by speaker designers to minimize driver overlap distortion.
About this calculator
A crossover frequency splits the audio signal so the woofer handles low frequencies and the tweeter handles high frequencies. The optimal crossover point is the geometric mean of the two drivers' usable frequency boundaries: crossoverFreq = √(wooferFreq × tweeterFreq). The geometric mean is used rather than the arithmetic mean because human pitch perception is logarithmic — equal ratios sound equally spaced. For example, 800 Hz is perceptually halfway between 200 Hz and 3200 Hz. Choosing the geometric mean places the crossover at the perceptual midpoint, minimizing the audible transition. Speaker impedance and crossover order (first, second, or fourth order) determine the values of the inductor and capacitor components needed to physically implement the filter, though those component calculations extend beyond this formula.
How to use
Suppose your woofer's upper usable limit is 2,000 Hz and your tweeter's lower usable limit is 8,000 Hz. Calculation: crossoverFreq = √(2,000 × 8,000) = √16,000,000 = 4,000 Hz. Set your crossover at 4,000 Hz. This places the handoff point at the geometric midpoint between the two drivers, ensuring each driver operates well within its comfortable range and the transition region is centered perceptually. Verify by checking that both drivers are at least 6 dB down from their respective roll-off edges at this frequency.
Frequently asked questions
What is the geometric mean and why is it used to calculate speaker crossover frequency?
The geometric mean of two numbers is the square root of their product: √(a × b). It is used for crossover frequency because human hearing perceives pitch on a logarithmic scale rather than a linear one. On a logarithmic scale, the geometric mean sits exactly halfway between two frequencies. Placing the crossover at the geometric mean ensures equal frequency-ratio margins for both the woofer and tweeter, which sounds like a centered, balanced handoff rather than one driver being pushed closer to its limits than the other.
How does speaker impedance affect crossover component values in a passive crossover network?
Impedance determines the resistance the crossover filter must work against, which directly sets the required inductor and capacitor values. For a first-order crossover, the inductor value is L = Z / (2π × f) and the capacitor value is C = 1 / (2π × f × Z), where Z is the speaker impedance in ohms and f is the crossover frequency. Lower impedance speakers (4 Ω) need larger capacitors and smaller inductors than 8 Ω speakers at the same crossover frequency. Using the wrong impedance value will shift the actual crossover point away from the calculated target.
What crossover order should I choose for a home hi-fi speaker build?
Crossover order determines how steeply the filter attenuates frequencies beyond the crossover point. A first-order crossover rolls off at 6 dB per octave — gentle and phase-coherent but offering little driver protection. Second-order (12 dB/octave) is the most common choice in home hi-fi because it balances component simplicity with adequate rejection. Fourth-order Linkwitz-Riley designs (24 dB/octave) are popular in audiophile builds for their flat summed response and deep driver isolation. Higher-order crossovers require more components and more precise construction but protect drivers more effectively from out-of-band signals.