Problem: Box Sounds Boomy / One-Note Bass

Symptoms: Bass emphasizes one frequency range, sounds unnatural, certain notes dominate

Diagnosis flowchart:

Step 1: Play swept sine tone (20–200 Hz) at moderate volume. Listen for pronounced peak or resonance.

If resonance at 40–60 Hz: - Likely cause: Ported box tuned too high or sealed box too small (Qtc too high) - Fix: Verify box volume calculation. If sealed and Qtc > 1.0, box is undersized. - Measurement: Use REW to measure response. Look for peak at Fc or Fb.

If resonance at 80–150 Hz: - Likely cause: Panel resonance or vehicle cabin mode - Fix: Add internal bracing. Apply damping material to largest panels. - Test: Press firmly on exterior panels while playing bass. If resonance changes = panel issue.

If boomy at all bass frequencies: - Likely cause: Subwoofer level too high relative to front speakers - Fix: Reduce subwoofer amp gain by 3 dB. Re-evaluate with music.

Step 2: Check crossover settings.

High crossover (>100 Hz) makes subwoofer location obvious. Lower to 80 Hz maximum.

Step 3: Verify polarity.

Reverse polarity at subwoofer terminals. If bass tightens up = polarity was wrong.