Altec Lansing 904-8A
Best box: 31.3 L bass reflex tuned to 66.7 Hz · F3 89.0 Hz
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Comparable 15.0" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the Altec Lansing 904-8A 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: 3.302 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) | 31.3 Liters |
| Tuning Frequency (Fb) | 66.7 Hz |
| F3 (-3 dB Cutoff) | 89.0 Hz |
| F6 / F10 Extension | 73.8 Hz / 61.3 Hz |
| Port Inner Diameter | Ø 10.0 cm |
| Port Physical Length | 9.8 cm |
| First Pipe Resonance | 1763.0 Hz |
| Estimated MOL @ F3 | 124.8 dB SPL |
Recommended Sealed (Acoustic Suspension)
MAX TRANSIENT DAMPING| Net Box Volume (Vb) | 21.7 Liters |
| System Q (Qtc) | 0.707 (Butterworth) |
| System Resonance (Fc) | 123.6 Hz |
| F3 (-3 dB Cutoff) | 116.8 Hz |
| F6 / F10 Extension | 90.2 Hz / 68.7 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 30.5 Hz |
| Total Q (Qts) | 0.16 |
| Electrical Q (Qes) | 0.175 |
| Mechanical Q (Qms) | 1.83 |
| Equivalent Volume (Vas) | 401.5 Liters |
| Diaphragm Area (Sd) | 804.0 cm² |
| DC Resistance (Re) | 5.2 Ω |
| Efficiency Bandwidth Product (EBP) | 174.0 |
| Linear Excursion (Xmax) | 3.3 mm |
| Thermal Power (Pe) | N/A W |
| Nominal Diameter | 15.0" |
| 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 904-8A?
Load Forge's calculated alignment puts Altec Lansing 904-8A in a 31.3 liter vented enclosure tuned to 66.7 Hz, reaching an F3 cutoff of approximately 89.0 Hz.
Can Altec Lansing 904-8A be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 21.7 liters with a Qtc of 0.707 (Butterworth), the system exhibits an F3 of 116.8 Hz.
What port dimensions should be used for Altec Lansing 904-8A to avoid port chuffing?
Sized from cone displacement (Sd × Xmax), a minimum port diameter of 10.0 cm with a length of 9.8 cm is suggested; check the port air velocity at your drive level in the Load Forge Studio.
Shareable Acoustic Card for Forums & Social Media
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