Problem: Distorted Bass at High Volume

Symptoms: Clean at low/moderate volume, distorted or farty-sounding at high volume

Diagnosis decision tree:

Is distortion only on very deep bass (<35 Hz)? - YES: Driver over-excursion (mechanical limit) - Playing below box tuning frequency (ported) without subsonic filter - Fix: Enable subsonic filter, reduce deep bass content, or larger box with lower tuning

• NO, distorts at all bass frequencies: Continue to next step

Is amplifier gain set correctly? - Test: Play 0 dBFS test tone at 75% head unit volume. Measure amplifier output with DMM. - Should match: V = √(Power × Impedance) - If reading is higher = gain too high, amplifier clipping - Fix: Reduce gain until DMM reading matches target voltage

Is distortion intermittent / worse when engine off? - YES: Voltage sag / insufficient power system - Amplifier going into protection or clipping due to low voltage - Fix: Upgrade electrical system (Chapter 11)

• NO, distorts consistently: Driver may be damaged

Physical test: - Remove subwoofer from enclosure - Press cone gently while listening for scraping - Scraping = voice coil damage, replace driver - Smooth movement = check wiring for short or partial short