Passive Radiator / Folded Port

SICA 6.5 H 1.5 CP

Best box: 11.0 L sealed · Fc 74.5 Hz · F3 75.4 Hz

Predicted SPL response of the SICA 6.5 H 1.5 CP in the recommended 11.0 L sealed box versus the alternative — open it in the simulator Open and tweak this box live ↗

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⚠️ Engineering Notice for Builders

  • Straight vent would be 208.8 cm long: not physically buildable as a simple tube. Use a passive radiator, a folded slot port or model a 3D folded duct in Load Forge Studio.

Textbook Bass Reflex — not recommended

PORT NOT BUILDABLE
Net Box Volume (Vb) 25.1 Liters
Tuning Frequency (Fb) 41.6 Hz
F3 (-3 dB Cutoff) 39.0 Hz
F6 / F10 Extension 35.0 Hz / 31.2 Hz
Port Inner Diameter Ø 20.3 cm
Port Physical Length 208.8 cm
First Pipe Resonance 82.0 Hz
Estimated MOL @ F3 105.5 dB SPL
⚠️ Port feasibility: a straight tube would need 208.8 cm and cannot fit in a practical cabinet, and no nearby retune stays buildable without a bass hump. Prefer the sealed alignment, a passive radiator, or a 3D folded duct in Load Forge Studio.
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Recommended Sealed (Acoustic Suspension)

MAX TRANSIENT DAMPING
Net Box Volume (Vb) 11.0 Liters
System Q (Qtc) 0.707 (Butterworth)
System Resonance (Fc) 74.5 Hz
F3 (-3 dB Cutoff) 75.4 Hz
F6 / F10 Extension 56.8 Hz / 42.8 Hz
Air Spring Linearity High (Zero port compression)
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Thiele/Small Parameters

Resonance (Fs) 45.4 Hz
Total Q (Qts) 0.42
Electrical Q (Qes) 0.457
Mechanical Q (Qms) 5.21
Equivalent Volume (Vas) 20.2 Liters
Diaphragm Area (Sd) 122.7 cm²
DC Resistance (Re) 6.1 Ω
Efficiency Bandwidth Product (EBP) 99.4
Linear Excursion (Xmax) 174.0 mm
Thermal Power (Pe) 120.0 W
Nominal Diameter 6.0"
Catalog Source Load Forge catalog (manufacturer datasheets and retailer listings)

Frequently Asked Questions

What is the recommended ported (bass reflex) box volume for SICA 6.5 H 1.5 CP?

A simple ported box is not recommended for SICA 6.5 H 1.5 CP: the textbook alignment (25.1 liters tuned to 41.6 Hz) needs a 208.8 cm port, and no nearby retune stays buildable without a bass hump. A sealed box, a passive radiator or a folded duct is the practical choice.

Can SICA 6.5 H 1.5 CP be used in a sealed box?

Yes. In a sealed (acoustic suspension) enclosure of 11.0 liters with a Qtc of 0.707 (Butterworth), the system exhibits an F3 of 75.4 Hz.

What port dimensions should be used for SICA 6.5 H 1.5 CP to avoid port chuffing?

A straight 20.3 cm port would need 208.8 cm of length, which does not fit a practical cabinet. Use a passive radiator or a folded/3D duct instead of a straight tube.

Shareable Acoustic Card for Forums & Social Media

Embed this design card on DIYAudio, AVSForum, Reddit, or Facebook. It shows the calculated F3, MOL (when the power rating is published) and box parameters.

SICA 6.5 H 1.5 CP Enclosure Card
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