Focal P 25 FSE slim 25 cm
Best box: 20.0 L bass reflex tuned to 25.5 Hz · F3 37.5 Hz
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Comparable 8.4" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the Focal P 25 FSE slim 25 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
- Port length (78.8 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) | 20.0 Liters |
| Tuning Frequency (Fb) | 25.5 Hz |
| F3 (-3 dB Cutoff) | 37.5 Hz |
| F6 / F10 Extension | 31.4 Hz / 24.2 Hz |
| Port Inner Diameter | Ø 6.8 cm |
| Port Physical Length | 78.8 cm |
| First Pipe Resonance | 218.0 Hz |
| Estimated MOL @ F3 | 105.7 dB SPL |
Sealed (Acoustic Suspension) — compromise
SUITS INFINITE / OPEN BAFFLEWith Qts 0.78 a Butterworth (Qtc 0.707) box would be many times Vas. A box equal to Vas reaches Qtc 1.103; for a flat response this driver is better used on an infinite (IB) or open baffle.
| Net Box Volume (Vb) | 25.0 Liters |
| System Q (Qtc) | 1.103 (above Butterworth: Qtc cannot fall below Qts (0.78)) |
| System Resonance (Fc) | 42.4 Hz |
| F3 (-3 dB Cutoff) | 35.6 Hz |
| F6 / F10 Extension | 29.6 Hz / 23.9 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 30.0 Hz |
| Total Q (Qts) | 0.78 |
| Electrical Q (Qes) | 0.924 |
| Mechanical Q (Qms) | 5.0 |
| Equivalent Volume (Vas) | 25.0 Liters |
| Diaphragm Area (Sd) | 346.0 cm² |
| DC Resistance (Re) | 3.2 Ω |
| Efficiency Bandwidth Product (EBP) | 32.5 |
| Linear Excursion (Xmax) | 11.0 mm |
| Thermal Power (Pe) | 280.0 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 25 FSE slim 25 cm?
Load Forge's calculated alignment puts Focal P 25 FSE slim 25 cm in a 20.0 liter vented enclosure tuned to 25.5 Hz, reaching an F3 cutoff of approximately 37.5 Hz.
Can Focal P 25 FSE slim 25 cm be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 25.0 liters with a Qtc of 1.103 (above Butterworth: Qtc cannot fall below Qts (0.78)), the system exhibits an F3 of 35.6 Hz.
What port dimensions should be used for Focal P 25 FSE slim 25 cm to avoid port chuffing?
Sized from cone displacement (Sd × Xmax), a minimum port diameter of 6.8 cm with a length of 78.8 cm is suggested; check the port air velocity at your drive level in the Load Forge Studio.
Shareable Acoustic Card for Forums & Social Media
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