Vented Specialist

Altec Lansing 6 x 9-4B

Best box: 8.4 L bass reflex tuned to 82.0 Hz · F3 94.8 Hz

Predicted SPL response of the Altec Lansing 6 x 9-4B in the recommended 8.4 L bass reflex box versus the alternative — open it in the simulator Open and tweak this box live ↗

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⚠️ Engineering Notice for Builders

  • Limited linear excursion (Xmax: 1.778 mm); set a high-pass subsonic filter at 25–30 Hz when driven with high power.

Recommended Bass Reflex (Vented)

PORT BUILDABLE
Net Box Volume (Vb) 8.4 Liters
Tuning Frequency (Fb) 82.0 Hz
F3 (-3 dB Cutoff) 94.8 Hz
F6 / F10 Extension 80.8 Hz / 68.8 Hz
Port Inner Diameter Ø 5.0 cm
Port Physical Length 6.8 cm
First Pipe Resonance 2513.0 Hz
Estimated MOL @ F3 111.9 dB SPL
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Recommended Sealed (Acoustic Suspension)

MAX TRANSIENT DAMPING
Net Box Volume (Vb) 4.6 Liters
System Q (Qtc) 0.707 (Butterworth)
System Resonance (Fc) 152.2 Hz
F3 (-3 dB Cutoff) 134.4 Hz
F6 / F10 Extension 105.4 Hz / 80.7 Hz
Air Spring Linearity High (Zero port compression)
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Thiele/Small Parameters

Resonance (Fs) 50.0 Hz
Total Q (Qts) 0.22
Electrical Q (Qes) 0.258
Mechanical Q (Qms) 1.48
Equivalent Volume (Vas) 43.0 Liters
Diaphragm Area (Sd) 184.3 cm²
DC Resistance (Re) 3.0 Ω
Efficiency Bandwidth Product (EBP) 193.5
Linear Excursion (Xmax) 1.8 mm
Thermal Power (Pe) N/A 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 Altec Lansing 6 x 9-4B?

Load Forge's calculated alignment puts Altec Lansing 6 x 9-4B in a 8.4 liter vented enclosure tuned to 82.0 Hz, reaching an F3 cutoff of approximately 94.8 Hz.

Can Altec Lansing 6 x 9-4B be used in a sealed box?

Yes. In a sealed (acoustic suspension) enclosure of 4.6 liters with a Qtc of 0.707 (Butterworth), the system exhibits an F3 of 134.4 Hz.

What port dimensions should be used for Altec Lansing 6 x 9-4B to avoid port chuffing?

Sized from cone displacement (Sd × Xmax), a minimum port diameter of 5.0 cm with a length of 6.8 cm is suggested; check the port air velocity at your drive level in the Load Forge Studio.

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.

Altec Lansing 6 x 9-4B Enclosure Card
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