Subwoofer Over-Excursion

Symptom: Subwoofer moving violently, sounds like it's "slapping" or bottoming out. May hear a hard clicking or thumping mechanical sound at bass peaks.

Cause: Cone traveling beyond mechanical limits (Xmax or Xmech). This will damage the surround, spider, and voice coil.

Immediate action: Reduce volume or increase high-pass (subsonic) filter frequency.

Root causes:

1. No subsonic filter on ported enclosure — Ported boxes offer no mechanical protection below tuning frequency. Below tuning, impedance drops and excursion spikes dramatically. Subsonic filter at 5–10 Hz below tuning frequency is mandatory.

2. Gain too high — Amplifier clipping increases average power beyond driver ratings.

3. Underpowered amplifier clipping — Clipped square waves have very high average power. A 200W amp clipping hard can damage a 500W speaker.

4. Box too large (sealed) — Oversized sealed box reduces air spring, allowing more excursion.

5. Program material with extreme low-frequency content — Some EDM and pipe organ recordings contain 20–30 Hz content that drives massive excursion. Subsonic filter protects.