SICA 18 PF 4
Best box: 86.5 L sealed · Fc 59.9 Hz · F3 61.2 Hz
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Comparable 18.0" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the SICA 18 PF 4 does not fit your target box volume or tuning. Each entry links to its full enclosure design and Thiele/Small parameters.
⚠️ Engineering Notice for Builders
- Straight vent would be 817.7 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.
- Large enclosure volume (196.0 L) requires extensive internal matrix bracing to prevent panel resonance.
Textbook Bass Reflex — not recommended
PORT NOT BUILDABLE| Net Box Volume (Vb) | 196.0 Liters |
| Tuning Frequency (Fb) | 34.1 Hz |
| F3 (-3 dB Cutoff) | 31.5 Hz |
| F6 / F10 Extension | 28.5 Hz / 25.4 Hz |
| Port Inner Diameter | Ø 92.5 cm |
| Port Physical Length | 817.7 cm |
| First Pipe Resonance | 21.0 Hz |
| Estimated MOL @ F3 | 121.4 dB SPL |
Recommended Sealed (Acoustic Suspension)
MAX TRANSIENT DAMPING| Net Box Volume (Vb) | 86.5 Liters |
| System Q (Qtc) | 0.707 (Butterworth) |
| System Resonance (Fc) | 59.9 Hz |
| F3 (-3 dB Cutoff) | 61.2 Hz |
| F6 / F10 Extension | 46.0 Hz / 34.7 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 38.0 Hz |
| Total Q (Qts) | 0.43 |
| Electrical Q (Qes) | 0.461 |
| Mechanical Q (Qms) | 6.46 |
| Equivalent Volume (Vas) | 147.3 Liters |
| Diaphragm Area (Sd) | 1164.2 cm² |
| DC Resistance (Re) | 5.2 Ω |
| Efficiency Bandwidth Product (EBP) | 82.5 |
| Linear Excursion (Xmax) | 463.0 mm |
| Thermal Power (Pe) | 1200.0 W |
| Nominal Diameter | 18.0" |
| Catalog Source | Load Forge catalog (manufacturer datasheets and retailer listings) |
Frequently Asked Questions
What is the recommended ported (bass reflex) box volume for SICA 18 PF 4?
A simple ported box is not recommended for SICA 18 PF 4: the textbook alignment (196.0 liters tuned to 34.1 Hz) needs a 817.7 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 18 PF 4 be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 86.5 liters with a Qtc of 0.707 (Butterworth), the system exhibits an F3 of 61.2 Hz.
What port dimensions should be used for SICA 18 PF 4 to avoid port chuffing?
A straight 92.5 cm port would need 817.7 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
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