Simple Explanation

A filter that lets the low sounds through and blocks or reduces the high ones.

Concise Technical Definition

A filter with a passband extending from DC (0 Hz) to a finite cutoff frequency, allowing lower frequencies to pass while attenuating all frequencies above that point.

Layman-Friendly Analogy

Like a doorway that only short people (low sounds) can walk through—taller ones (high sounds) get blocked.

Industry Usage Summary

Low-pass filters are widely used in speaker crossovers, subwoofers, and signal processing systems. They are also essential in digital systems as anti-aliasing (pre-conversion) and anti-imaging (post-conversion) filters to control bandwidth and prevent unwanted frequencies. Sometimes referred to as high-cut filters.

Engineering Shortcut

Passes low frequencies, cuts highs above set cutoff; used in crossover and DSP.

Full Technical Explanation

A low-pass filter is a circuit or signal-processing function that allows frequencies from DC (0 Hz) up to a specified cutoff frequency to pass through unaltered, while attenuating frequencies above that point. It is the opposite of a high-pass filter, and may also be called a high-cut filter. In analog and digital applications, low-pass filters are used to limit bandwidth and remove unwanted high-frequency content. In digital audio, they serve as anti-aliasing filters before analog-to-digital conversion and anti-imaging filters after digital-to-analog conversion. In speaker systems, low-pass filters route only bass frequencies to subwoofers or woofers. Their effectiveness depends on the filter order, which determines how steeply the signal rolls off past the cutoff frequency (e.g., 12 dB/octave, 24 dB/octave).