Fi Car Audio Q v4 18
Best box: 162.8 L bass reflex tuned to 27.9 Hz · F3 28.4 Hz
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Comparable 18.0" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the Fi Car Audio Q v4 18 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
- Port length (66.9 cm) exceeds a straight internal run; use an elbow bend, slotted vent or 3D folded duct to fit the enclosure.
- Large enclosure volume (162.8 L) requires extensive internal matrix bracing to prevent panel resonance.
Recommended Bass Reflex (Vented)
PORT NEEDS ELBOW / 3D| Net Box Volume (Vb) | 162.8 Liters |
| Tuning Frequency (Fb) | 27.9 Hz |
| F3 (-3 dB Cutoff) | 28.4 Hz |
| F6 / F10 Extension | 24.9 Hz / 21.7 Hz |
| Port Inner Diameter | Ø 21.0 cm |
| Port Physical Length | 66.9 cm |
| First Pipe Resonance | 257.0 Hz |
| Estimated MOL @ F3 | 121.1 dB SPL |
Recommended Sealed (Acoustic Suspension)
MAX TRANSIENT DAMPING| Net Box Volume (Vb) | 72.2 Liters |
| System Q (Qtc) | 0.707 (Butterworth) |
| System Resonance (Fc) | 50.8 Hz |
| F3 (-3 dB Cutoff) | 52.5 Hz |
| F6 / F10 Extension | 39.4 Hz / 29.7 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 25.2 Hz |
| Total Q (Qts) | 0.34 |
| Electrical Q (Qes) | 0.361 |
| Mechanical Q (Qms) | 5.8 |
| Equivalent Volume (Vas) | 240.0 Liters |
| Diaphragm Area (Sd) | 1210.0 cm² |
| DC Resistance (Re) | 3.6 Ω |
| Efficiency Bandwidth Product (EBP) | 69.8 |
| Linear Excursion (Xmax) | 28.0 mm |
| Thermal Power (Pe) | 1750.0 W |
| Nominal Diameter | 18.0" |
| Catalog Source | Load Forge catalog (manufacturer datasheets and retailer listings) |
Frequently Asked Questions
What is the recommended ported (bass reflex) box volume for Fi Car Audio Q v4 18?
Load Forge's calculated alignment puts Fi Car Audio Q v4 18 in a 162.8 liter vented enclosure tuned to 27.9 Hz, reaching an F3 cutoff of approximately 28.4 Hz.
Can Fi Car Audio Q v4 18 be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 72.2 liters with a Qtc of 0.707 (Butterworth), the system exhibits an F3 of 52.5 Hz.
What port dimensions should be used for Fi Car Audio Q v4 18 to avoid port chuffing?
Sized from cone displacement (Sd × Xmax), a minimum port diameter of 21.0 cm with a length of 66.9 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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