Simple Explanation

A type of audio filter that smoothly splits sound between speakers like woofers and tweeters, so nothing overlaps or cancels out.

Concise Technical Definition

A crossover filter design using two cascaded 2nd-order Butterworth filters to achieve a 4th-order (24 dB/octave) slope with flat summed frequency response and in-phase outputs at the crossover point.

Layman-Friendly Analogy

Like handing off a baton in a relay race so smoothly that there’s no gap or clash between runners.

Industry Usage Summary

Widely used in active speaker systems and DSP-based crossovers for its steep 24 dB/octave rolloff and phase-coherent summing; replaces older 3rd-order Butterworth designs in most professional applications.

Engineering Shortcut

LR-4 = cascaded Butterworth 2nd-order filters; 24 dB/octave, in-phase.

Full Technical Explanation

The Linkwitz-Riley crossover, commonly abbreviated as LR-4, is a filter topology used to divide audio signals between drivers (e.g., woofers and tweeters) in multiway loudspeaker systems. It is formed by cascading two 2nd-order Butterworth filters (low-pass and high-pass), resulting in a 4th-order filter with a 24 dB/octave slope. The advantage of the LR-4 design is that the outputs are in phase at the crossover frequency and sum to a flat frequency response, minimizing both amplitude and phase anomalies at the crossover point. This makes it the standard choice in active crossover networks for professional and high-fidelity audio systems. It improves upon earlier Butterworth filters by reducing lobing and phase issues in the transition region between drivers.