Altec Lansing 421-8H
Best box: 101.7 L bass reflex tuned to 46.1 Hz · F3 50.1 Hz
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Comparable 15.0" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the Altec Lansing 421-8H 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: 1.27 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) | 101.7 Liters |
| Tuning Frequency (Fb) | 46.1 Hz |
| F3 (-3 dB Cutoff) | 50.1 Hz |
| F6 / F10 Extension | 43.5 Hz / 37.5 Hz |
| Port Inner Diameter | Ø 10.0 cm |
| Port Physical Length | 3.7 cm |
| First Pipe Resonance | 4596.0 Hz |
| Estimated MOL @ F3 | 113.8 dB SPL |
Recommended Sealed (Acoustic Suspension)
MAX TRANSIENT DAMPING| Net Box Volume (Vb) | 51.8 Liters |
| System Q (Qtc) | 0.707 (Butterworth) |
| System Resonance (Fc) | 82.0 Hz |
| F3 (-3 dB Cutoff) | 84.4 Hz |
| F6 / F10 Extension | 63.3 Hz / 47.5 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 31.5 Hz |
| Total Q (Qts) | 0.25 |
| Electrical Q (Qes) | 0.277 |
| Mechanical Q (Qms) | 2.6 |
| Equivalent Volume (Vas) | 362.5 Liters |
| Diaphragm Area (Sd) | 825.8 cm² |
| DC Resistance (Re) | 5.5 Ω |
| Efficiency Bandwidth Product (EBP) | 113.9 |
| Linear Excursion (Xmax) | 1.3 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 421-8H?
Load Forge's calculated alignment puts Altec Lansing 421-8H in a 101.7 liter vented enclosure tuned to 46.1 Hz, reaching an F3 cutoff of approximately 50.1 Hz.
Can Altec Lansing 421-8H be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 51.8 liters with a Qtc of 0.707 (Butterworth), the system exhibits an F3 of 84.4 Hz.
What port dimensions should be used for Altec Lansing 421-8H to avoid port chuffing?
Sized from cone displacement (Sd × Xmax), a minimum port diameter of 10.0 cm with a length of 3.7 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.
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