Focal P 20 FSESlim subwoofer 20 cm
Best box: 9.0 L sealed · Fc 49.5 Hz · F3 40.7 Hz
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Comparable 8.4" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the Focal P 20 FSESlim subwoofer 20 cm 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
- Straight vent would be 165.4 cm long: not physically buildable as a simple tube. Use a passive radiator, a folded slot port or model a 3D folded duct in Load Forge Studio.
Textbook Bass Reflex — not recommended
PORT NOT BUILDABLE| Net Box Volume (Vb) | 7.2 Liters |
| Tuning Frequency (Fb) | 29.8 Hz |
| F3 (-3 dB Cutoff) | 47.0 Hz |
| F6 / F10 Extension | 41.5 Hz / 34.6 Hz |
| Port Inner Diameter | Ø 6.8 cm |
| Port Physical Length | 165.4 cm |
| First Pipe Resonance | 104.0 Hz |
| Estimated MOL @ F3 | 102.5 dB SPL |
Sealed (Acoustic Suspension) — compromise
SUITS INFINITE / OPEN BAFFLEWith Qts 1.3 a Butterworth (Qtc 0.707) box would be many times Vas. A box equal to Vas reaches Qtc 1.838; for a flat response this driver is better used on an infinite (IB) or open baffle.
| Net Box Volume (Vb) | 9.0 Liters |
| System Q (Qtc) | 1.838 (above Butterworth: Qtc cannot fall below Qts (1.30)) |
| System Resonance (Fc) | 49.5 Hz |
| F3 (-3 dB Cutoff) | 40.7 Hz |
| F6 / F10 Extension | 35.8 Hz / 30.3 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 35.0 Hz |
| Total Q (Qts) | 1.3 |
| Electrical Q (Qes) | 1.757 |
| Mechanical Q (Qms) | 5.0 |
| Equivalent Volume (Vas) | 9.0 Liters |
| Diaphragm Area (Sd) | 213.0 cm² |
| DC Resistance (Re) | 3.2 Ω |
| Efficiency Bandwidth Product (EBP) | 19.9 |
| Linear Excursion (Xmax) | 11.0 mm |
| Thermal Power (Pe) | 200.0 W |
| Nominal Diameter | 8.4" |
| Catalog Source | Load Forge catalog (manufacturer datasheets and retailer listings) |
Frequently Asked Questions
What is the recommended ported (bass reflex) box volume for Focal P 20 FSESlim subwoofer 20 cm?
A simple ported box is not recommended for Focal P 20 FSESlim subwoofer 20 cm: the textbook alignment (7.2 liters tuned to 29.8 Hz) needs a 165.4 cm port, and no nearby retune stays buildable without a bass hump. A sealed box, a passive radiator or a folded duct is the practical choice.
Can Focal P 20 FSESlim subwoofer 20 cm be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 9.0 liters with a Qtc of 1.838 (above Butterworth: Qtc cannot fall below Qts (1.30)), the system exhibits an F3 of 40.7 Hz.
What port dimensions should be used for Focal P 20 FSESlim subwoofer 20 cm to avoid port chuffing?
A straight 6.8 cm port would need 165.4 cm of length, which does not fit a practical cabinet. Use a passive radiator or a folded/3D duct instead of a straight tube.
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