Fostex FE103A-VB
Best box: 6.8 L bass reflex tuned to 61.1 Hz · F3 71.9 Hz
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Comparable 4.0" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the Fostex FE103A-VB 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) | 6.8 Liters |
| Tuning Frequency (Fb) | 61.1 Hz |
| F3 (-3 dB Cutoff) | 71.9 Hz |
| F6 / F10 Extension | 54.3 Hz / 46.6 Hz |
| Port Inner Diameter ESTIMATED | Ø 5.0 cm |
| Port Physical Length | 19.6 cm |
| First Pipe Resonance | 877.0 Hz |
Recommended Sealed (Acoustic Suspension)
MAX TRANSIENT DAMPING| Net Box Volume (Vb) | 7.0 Liters |
| System Q (Qtc) | 0.707 (Butterworth) |
| System Resonance (Fc) | 105.7 Hz |
| F3 (-3 dB Cutoff) | 107.5 Hz |
| F6 / F10 Extension | 81.3 Hz / 61.4 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 85.0 Hz |
| Total Q (Qts) | 0.55 |
| Electrical Q (Qes) | 0.607 |
| Mechanical Q (Qms) | 5.82 |
| Equivalent Volume (Vas) | 4.5 Liters |
| Diaphragm Area (Sd) | 50.3 cm² |
| DC Resistance (Re) | 6.7 Ω |
| Efficiency Bandwidth Product (EBP) | 139.9 |
| 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 FE103A-VB?
Load Forge's calculated alignment puts Fostex FE103A-VB in a 6.8 liter vented enclosure tuned to 61.1 Hz, reaching an F3 cutoff of approximately 71.9 Hz.
Can Fostex FE103A-VB be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 7.0 liters with a Qtc of 0.707 (Butterworth), the system exhibits an F3 of 107.5 Hz.
What port dimensions should be used for Fostex FE103A-VB to avoid port chuffing?
Xmax is not published for Fostex FE103A-VB, so the port is an empirical estimate: a 5.0 cm diameter with a length of 19.6 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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