Fountek FW100B
Best box: 1.7 L bass reflex tuned to 85.2 Hz · F3 100.4 Hz
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Comparable 4.0" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the Fountek FW100B 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
- The textbook alignment (1.7 L at 65.5 Hz) would need a 77.1 cm port; the recommendation is retuned to 1.7 L at 85.2 Hz so the port can be built.
- 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) | 1.7 Liters |
| Tuning Frequency (Fb) | 85.2 Hz |
| F3 (-3 dB Cutoff) | 100.4 Hz |
| F6 / F10 Extension | 84.9 Hz / 69.3 Hz |
| Port Inner Diameter ESTIMATED | Ø 5.0 cm |
| Port Physical Length | 44.1 cm |
| First Pipe Resonance | 390.0 Hz |
| Estimated MOL @ F3 | 99.4 dB SPL |
Sealed (Acoustic Suspension) — compromise
SUITS INFINITE / OPEN BAFFLEWith Qts 0.63 a Butterworth (Qtc 0.707) box would be many times Vas. A box equal to Vas reaches Qtc 0.891; for a flat response this driver is better used on an infinite (IB) or open baffle.
| Net Box Volume (Vb) | 2.1 Liters |
| System Q (Qtc) | 0.891 (above Butterworth) |
| System Resonance (Fc) | 108.9 Hz |
| F3 (-3 dB Cutoff) | 98.6 Hz |
| F6 / F10 Extension | 79.7 Hz / 62.9 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 77.0 Hz |
| Total Q (Qts) | 0.63 |
| Electrical Q (Qes) | 0.791 |
| Mechanical Q (Qms) | 3.09 |
| Equivalent Volume (Vas) | 2.1 Liters |
| Diaphragm Area (Sd) | 55.4 cm² |
| DC Resistance (Re) | 6.2 Ω |
| Efficiency Bandwidth Product (EBP) | 97.3 |
| Linear Excursion (Xmax) | N/A mm |
| Thermal Power (Pe) | 35.0 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 Fountek FW100B?
Load Forge's calculated alignment puts Fountek FW100B in a 1.7 liter vented enclosure tuned to 85.2 Hz, reaching an F3 cutoff of approximately 100.4 Hz.
Can Fountek FW100B be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 2.1 liters with a Qtc of 0.891 (above Butterworth), the system exhibits an F3 of 98.6 Hz.
What port dimensions should be used for Fountek FW100B to avoid port chuffing?
Xmax is not published for Fountek FW100B, so the port is an empirical estimate: a 5.0 cm diameter with a length of 44.1 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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