Fostex FE108NS
Best box: 3.1 L bass reflex tuned to 87.8 Hz · F3 91.0 Hz
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Comparable 4.0" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the Fostex FE108NS 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
- Xmax is not published, so the port size is an empirical estimate (area ≥ 12 in² per ft³ of net volume, minimum by driver size), not a displacement calculation. Check air velocity in Load Forge Studio.
Recommended Bass Reflex (Vented)
PORT BUILDABLE| Net Box Volume (Vb) | 3.1 Liters |
| Tuning Frequency (Fb) | 87.8 Hz |
| F3 (-3 dB Cutoff) | 91.0 Hz |
| F6 / F10 Extension | 79.3 Hz / 68.8 Hz |
| Port Inner Diameter ESTIMATED | Ø 5.0 cm |
| Port Physical Length | 21.1 cm |
| First Pipe Resonance | 817.0 Hz |
Recommended Sealed (Acoustic Suspension)
MAX TRANSIENT DAMPING| Net Box Volume (Vb) | 1.4 Liters |
| System Q (Qtc) | 0.707 (Butterworth) |
| System Resonance (Fc) | 160.6 Hz |
| F3 (-3 dB Cutoff) | 157.5 Hz |
| F6 / F10 Extension | 121.0 Hz / 92.1 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 75.0 Hz |
| Total Q (Qts) | 0.32 |
| Electrical Q (Qes) | 0.357 |
| Mechanical Q (Qms) | 3.11 |
| Equivalent Volume (Vas) | 5.4 Liters |
| Diaphragm Area (Sd) | 49.0 cm² |
| DC Resistance (Re) | 7.4 Ω |
| Efficiency Bandwidth Product (EBP) | 210.3 |
| Linear Excursion (Xmax) | N/A mm |
| Thermal Power (Pe) | N/A W |
| Nominal Diameter | 4.0" |
| Catalog Source | Load Forge catalog (manufacturer datasheets and retailer listings) |
Frequently Asked Questions
What is the recommended ported (bass reflex) box volume for Fostex FE108NS?
Load Forge's calculated alignment puts Fostex FE108NS in a 3.1 liter vented enclosure tuned to 87.8 Hz, reaching an F3 cutoff of approximately 91.0 Hz.
Can Fostex FE108NS be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 1.4 liters with a Qtc of 0.707 (Butterworth), the system exhibits an F3 of 157.5 Hz.
What port dimensions should be used for Fostex FE108NS to avoid port chuffing?
Xmax is not published for Fostex FE108NS, so the port is an empirical estimate: a 5.0 cm diameter with a length of 21.1 cm (area at least 12 in² per ft³ of net volume). Check the air velocity at your power level in 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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