Altec Lansing 409-8D
Best box: 13.8 L bass reflex tuned to 77.3 Hz · F3 120.9 Hz
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Comparable 8.0" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the Altec Lansing 409-8D 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
- Limited linear excursion (Xmax: 1.524 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) | 13.8 Liters |
| Tuning Frequency (Fb) | 77.3 Hz |
| F3 (-3 dB Cutoff) | 120.9 Hz |
| F6 / F10 Extension | 108.3 Hz / 91.7 Hz |
| Port Inner Diameter | Ø 5.0 cm |
| Port Physical Length | 3.6 cm |
| First Pipe Resonance | 4828.0 Hz |
| Estimated MOL @ F3 | 109.3 dB SPL |
Sealed (Acoustic Suspension) — compromise
SUITS INFINITE / OPEN BAFFLEWith Qts 1.54 a Butterworth (Qtc 0.707) box would be many times Vas. A box equal to Vas reaches Qtc 2.178; for a flat response this driver is better used on an infinite (IB) or open baffle.
| Net Box Volume (Vb) | 17.3 Liters |
| System Q (Qtc) | 2.178 (above Butterworth: Qtc cannot fall below Qts (1.54)) |
| System Resonance (Fc) | 128.7 Hz |
| F3 (-3 dB Cutoff) | 103.5 Hz |
| F6 / F10 Extension | 92.3 Hz / 79.2 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 91.0 Hz |
| Total Q (Qts) | 1.54 |
| Electrical Q (Qes) | 1.778 |
| Mechanical Q (Qms) | 11.5 |
| Equivalent Volume (Vas) | 17.3 Liters |
| Diaphragm Area (Sd) | 209.7 cm² |
| DC Resistance (Re) | 6.9 Ω |
| Efficiency Bandwidth Product (EBP) | 51.2 |
| Linear Excursion (Xmax) | 1.5 mm |
| Thermal Power (Pe) | N/A 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 Altec Lansing 409-8D?
Load Forge's calculated alignment puts Altec Lansing 409-8D in a 13.8 liter vented enclosure tuned to 77.3 Hz, reaching an F3 cutoff of approximately 120.9 Hz.
Can Altec Lansing 409-8D be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 17.3 liters with a Qtc of 2.178 (above Butterworth: Qtc cannot fall below Qts (1.54)), the system exhibits an F3 of 103.5 Hz.
What port dimensions should be used for Altec Lansing 409-8D to avoid port chuffing?
Sized from cone displacement (Sd × Xmax), a minimum port diameter of 5.0 cm with a length of 3.6 cm is suggested; check the port air velocity at your drive level in the Load Forge Studio.
Shareable Acoustic Card for Forums & Social Media
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