Glossary
Cut-off frequency
Also: f3, −3 dB point, Low-frequency extension, F3
Definition
The lower cut-off frequency is the frequency at which the level has fallen by a defined amount below the average level – usually 3 dB (f3), sometimes 6 or 10 dB.
Unit: Hz
What to look out for
Link to section “What to look out for”- State the reference: “40 Hz” on its own says little. “40 Hz at −3 dB” and “40 Hz at −10 dB” describe very different enclosures.
- State the conditions: A value in half space or for four stacked enclosures is lower than for a single enclosure in full space.
- Simulated or measured: Many figures come from simulations.
Our plan pages also show the level reference and the conditions when the source states them. If the reference is missing, we say so.
Further reading
Link to section “Further reading”- Glossary Half space Half space (2π) means that a sound source stands on a large reflecting surface, such as the floor. Compared with full space (4π), the level rises by 3 dB in theory for the same sound power.
- Glossary Tuning frequency (Fb) The tuning frequency Fb is the resonant frequency formed by the enclosure volume and the port. Around this frequency it is mainly the port that radiates; the cone barely moves.
- Glossary High-pass A high-pass passes frequencies above its cut-off frequency and attenuates those below. With subwoofers it protects the driver from excessive excursion below the usable range.
Sources
Link to section “Sources”-
Tier B · secondary source
Wikipedia · accessed on 14 September 2026
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Tier B · secondary source
Wikipedia · accessed on 14 September 2026
Enclosure types: sealed (12 dB/oct.), bass reflex (24 dB/oct.), 4th- and 6th-order bandpass, transmission line/quarter wave, horn, tapped horn, isobaric.
Updated: 14 September 2026