Speaker Crossover Calculator

This speaker crossover calculator will help you design a set of amazing sounding speakers. It'll tell you what capacitors and inductors you need to create a passive crossover design for either two speakers (a 2-way passive crossover) or three speakers (a 3-way passive crossover).

In the 2-way mode, the calculator uses the impedance of your tweeter and woofer to produce a 2-way speaker crossover design. By choosing three speakers, it becomes a 3-way crossover calculator, in case you also want to incorporate a midrange speaker into your design.

There are also additional circuits for a single speaker: one to help stabilize the speaker's impedance as frequency changes (Zobel) and another that attenuates the volume (L-pad).

In this article, you'll learn why, if you want to get the best sound, you need more than one speaker, and how, by using the right electronic components, you can send only the most suitable frequencies to each speaker.

Why More Speakers Are Better Than One

If you are new to hi-fi speaker design, you might wonder why we can't just use one speaker. Devices like small portable radios or mobile phones have a single speaker but do they sound great at all frequencies?

A common complaint of single-speaker designs is the lack of bass response. Increasing speaker size may improve bass, but it reduces high frequency output. Hi-fi designs aim for consistent sound volume across a wide frequency range.

The solution is to have two or three specialist speakers: a tweeter for high frequencies, a woofer for low frequencies, and optionally a midrange driver for middle frequencies.

Passive Crossover Design

A passive crossover splits the signal from the amplifier according to frequency. Low-pass filters send low frequencies to the woofer, while high-pass filters send high frequencies to the tweeter.

For two speakers, this is a 2-way passive crossover; for three drivers, a 3-way passive crossover adds a band-pass filter for midrange. Passive designs require no additional power source.

This calculator is only applicable to passive crossovers. Typical crossover frequencies for 2-way systems are between 2000–3000 Hz.

Order and Filter Type

The filter order affects how steeply unwanted frequencies are attenuated:

• 1st order: 6 dB/octave slope, simplest design, minimal power loss.
• 2nd order: 12 dB/octave slope, good balance of complexity and quality.
• 3rd order: 18 dB/octave slope, more attenuation, still manageable complexity.
• 4th order: 24 dB/octave slope, steepest attenuation, but may cause interaction between components.

Example of Calculating a 2-Way Passive Crossover

Here is an example of a 2-way, 2nd-order Butterworth crossover with two capacitors and two inductors.

The equations for other orders and filter types are similar to those above but with varying constants. You can find all of these in the book by Vance Dickason called The Loudspeaker Design Cookbook, 7th edition (2006), pages 163-169.

Let's say we have a tweeter impedance of 6 Ohms, a woofer impedance of 4 Ohms, and a crossover frequency between the two of 3000 Hz. You would then calculate each component as:

Additional Circuits - Zobel and L-Pad

Zobel Circuit

A Zobel circuit stabilizes speaker impedance by adding a resistor and capacitor in parallel to the speaker.

L-Pad Circuit

An L-pad attenuates a speaker's volume using two resistors arranged in an “L” configuration.

FAQs

What is the value of the resistor in the Zobel circuit if the speaker's resistance is 8 Ω?

The resistor value, Rz, is 10 Ω (Rz = 1.25 × Rs).

What are the types of crossovers?

Passive, active, and digital.

How do I choose the right crossover frequency?

Check your driver specifications and choose a frequency covered by both speakers' response ranges.