Subwoofer Voice Coil Thermal Damage
Symptom: Subwoofer produces distorted sound, especially at sustained high levels. Performance degrades during a session and improves after cooling. Eventually fails permanently.
Mechanism: Voice coil heats up. Aluminum or copper wire resistance increases with temperature (Chapter 3). Higher resistance means less current for same voltage — "power compression." Eventually adhesives and insulation fail — permanent damage.
Prevention:
Correct gain setting — Most thermal failures result from continuous clipping, which dramatically increases average power delivered.
Adequate cooling — Subwoofer enclosures trap heat. Competition enclosures often have cooling vents with fans directed at the motor.
Duty cycle management — Continuous full-power bass requires a driver rated for that. Most subwoofers are rated for music-program power (dynamic), not continuous sine wave.
Adequate power headroom — Paradoxically, more amplifier power (without clipping) is safer than less power that clips. Clipping = DC content = maximum heating.