Passive Radiator / Folded Port

SB Acoustics SB12CACS25-8 Bass-midwoofer

Best box: 0.075 L sealed · Fc 97.4 Hz · F3 97.0 Hz

Predicted SPL response of the SB Acoustics SB12CACS25-8 Bass-midwoofer in the recommended 0.075 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 259.4 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) 1.5 Liters
Tuning Frequency (Fb) 52.4 Hz
F3 (-3 dB Cutoff) 49.1 Hz
F6 / F10 Extension 46.9 Hz / 43.9 Hz
Port Inner Diameter Ø 6.8 cm
Port Physical Length 259.4 cm
First Pipe Resonance 66.0 Hz
Estimated MOL @ F3 88.5 dB SPL
⚠️ Port feasibility: a straight tube would need 259.4 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) 0.075 Liters
System Q (Qtc) 0.707 (Butterworth)
System Resonance (Fc) 97.4 Hz
F3 (-3 dB Cutoff) 97.0 Hz
F6 / F10 Extension 73.7 Hz / 55.7 Hz
Air Spring Linearity High (Zero port compression)
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Thiele/Small Parameters

Resonance (Fs) 51.0 Hz
Total Q (Qts) 0.37
Electrical Q (Qes) 0.401
Mechanical Q (Qms) 4.85
Equivalent Volume (Vas) 0.2 Liters
Diaphragm Area (Sd) 220.0 cm²
DC Resistance (Re) 6.4 Ω
Efficiency Bandwidth Product (EBP) 127.3
Linear Excursion (Xmax) 5.0 mm
Thermal Power (Pe) 30.0 W
Nominal Diameter 8.0"
Catalog Source Load Forge catalog (manufacturer datasheets and retailer listings)

Frequently Asked Questions

What is the recommended ported (bass reflex) box volume for SB Acoustics SB12CACS25-8 Bass-midwoofer?

A simple ported box is not recommended for SB Acoustics SB12CACS25-8 Bass-midwoofer: the textbook alignment (1.5 liters tuned to 52.4 Hz) needs a 259.4 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 SB Acoustics SB12CACS25-8 Bass-midwoofer be used in a sealed box?

Yes. In a sealed (acoustic suspension) enclosure of 0.075 liters with a Qtc of 0.707 (Butterworth), the system exhibits an F3 of 97.0 Hz.

What port dimensions should be used for SB Acoustics SB12CACS25-8 Bass-midwoofer to avoid port chuffing?

A straight 6.8 cm port would need 259.4 cm of length, which does not fit a practical cabinet. Use a passive radiator or a folded/3D duct instead of a straight tube.

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SB Acoustics SB12CACS25-8 Bass-midwoofer Enclosure Card
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