Focal SUB 20 SF 200 mm
Best box: 12.1 L bass reflex tuned to 35.3 Hz · F3 34.2 Hz
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Comparable 7.9" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the Focal SUB 20 SF 200 mm 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 (67.3 cm) exceeds a straight internal run; use an elbow bend, slotted vent or 3D folded duct to fit the enclosure.
Recommended Bass Reflex (Vented)
PORT NEEDS ELBOW / 3D| Net Box Volume (Vb) | 12.1 Liters |
| Tuning Frequency (Fb) | 35.3 Hz |
| F3 (-3 dB Cutoff) | 34.2 Hz |
| F6 / F10 Extension | 30.4 Hz / 26.8 Hz |
| Port Inner Diameter | Ø 6.8 cm |
| Port Physical Length | 67.3 cm |
| First Pipe Resonance | 255.0 Hz |
| Estimated MOL @ F3 | 102.8 dB SPL |
Recommended Sealed (Acoustic Suspension)
MAX TRANSIENT DAMPING| Net Box Volume (Vb) | 5.2 Liters |
| System Q (Qtc) | 0.707 (Butterworth) |
| System Resonance (Fc) | 64.8 Hz |
| F3 (-3 dB Cutoff) | 66.4 Hz |
| F6 / F10 Extension | 49.9 Hz / 37.5 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 36.0 Hz |
| Total Q (Qts) | 0.39 |
| Electrical Q (Qes) | 0.435 |
| Mechanical Q (Qms) | 3.8 |
| Equivalent Volume (Vas) | 12.0 Liters |
| Diaphragm Area (Sd) | 202.0 cm² |
| DC Resistance (Re) | 2.8 Ω |
| Efficiency Bandwidth Product (EBP) | 82.8 |
| Linear Excursion (Xmax) | 10.0 mm |
| Thermal Power (Pe) | 200.0 W |
| Nominal Diameter | 7.9" |
| Catalog Source | Load Forge catalog (manufacturer datasheets and retailer listings) |
Frequently Asked Questions
What is the recommended ported (bass reflex) box volume for Focal SUB 20 SF 200 mm?
Load Forge's calculated alignment puts Focal SUB 20 SF 200 mm in a 12.1 liter vented enclosure tuned to 35.3 Hz, reaching an F3 cutoff of approximately 34.2 Hz.
Can Focal SUB 20 SF 200 mm be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 5.2 liters with a Qtc of 0.707 (Butterworth), the system exhibits an F3 of 66.4 Hz.
What port dimensions should be used for Focal SUB 20 SF 200 mm to avoid port chuffing?
Sized from cone displacement (Sd × Xmax), a minimum port diameter of 6.8 cm with a length of 67.3 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.
Not sure if SUB 20 SF 200 mm fits your physical space?
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