Problem: Sealed Box Sounds Peaky/Resonant

Symptom: Sealed enclosure should sound smooth, but has an obvious peak or emphasis at one frequency

Likely causes (in order):

1. Box volume too small → Qtc too high - Measure box internal volume carefully (length × width × height in inches ÷ 1728 = ft³) - Calculate actual Qtc: Qtc = Qts × √(Vas/Vb + 1) - If Qtc > 1.0, box is undersized for smooth response - Fix: Add polyfill (up to 0.75 lb/ft³) to increase effective volume ~15% - If still peaky, box must be enlarged

2. Panel resonance - Play swept sine 40–200 Hz, listen for panel rattle/vibration - Touch each panel during sweep — vibrating panel is resonating - Fix: Add cross-bracing inside box (requires opening and resealing)

3. Port open when it should be sealed - Verify port plug is fully seated and sealed - Air leak through port creates ported response from "sealed" box - Fix: Remove port tube or seal port opening permanently with silicone and wood plug

Measurement verification: - Measure impedance vs frequency - Sealed box shows single impedance peak at Fc - If two peaks visible = air leak creating partial vented response