Problem: Ported Box Plays Poorly Below Tuning

Symptom: Output drops off dramatically, sounds weak, or driver moves excessively at low frequencies

This is normal for ported enclosures. Below the port tuning frequency: - Port becomes inactive (no output from port) - Driver operates as if in infinite baffle (no acoustic loading) - Impedance drops, excursion spikes, distortion rises

Solutions:

1. Enable subsonic filter (mandatory for ported): - Set HPF frequency = Fb − 5 to 10 Hz - Set slope to 24 dB/octave minimum - Example: Box tuned 35 Hz → subsonic at 28 Hz, 24 dB/oct

2. Accept the limitation: - Ported boxes do not play well below tuning by design - If you need output at 25 Hz and box is tuned to 35 Hz, it won't deliver - Solution: Retune box lower (longer port, larger box) or use sealed

3. Verify tuning is correct: - Measure impedance, look for double peak - Valley between peaks = actual Fb - If Fb is higher than designed = port too short, lengthen port