Proline X
Performance Optimized Down Fire Sealed 10" Enclosure | Focal Flax Evo P 25 FSE
SKU: PO 10-S DF FSE
- Alignment: 0.80 cu ft net, Qtc 1.131, F3 32.6 Hz - computed from Focal's published T/S
- Driver: Focal Flax Evo P 25 FSE, 4Ω SVC, 280W RMS / 560W max, 11mm Xmax, flax fiber cone
- Build: Proline X V-groove and dado joinery, double-layer 1.5" front baffle, perimeter cross-brace, 12g OFC side-mounted terminal cup
- Cabinet: 30"W x 15"D x 6.125"H measured in down fire position, square corners
Financing available — choose Shop Pay Installments at checkout.
Performance Optimized Down Fire Sealed 10" Enclosure | Focal Flax Evo P 25 FSE
The Performance Optimized Down Fire Sealed 10" Enclosure for the Focal Flax Evo P 25 FSE is a low-profile sealed cabinet built around Focal's 10 inch flax-cone subwoofer. At 6.125 inches tall on a 30 by 15 inch footprint, it fits under seats and in cargo wells that will not accept a conventional box.
The Focal P 25 FSE is a 4Ω single voice coil subwoofer rated 280 watts RMS and 560 watts maximum, with 11mm of Xmax and 346 cm² of cone area. The construction is what sets Focal apart: a flax fiber cone sandwiched in their Flax Evo layup, rubber surround, and a 38mm four-layer copper voice coil on a glass fiber former. Flax is Focal's alternative to the usual polypropylene or treated paper, chosen for a favorable stiffness-to-mass ratio and internal damping.
The 0.80 cubic foot net volume produces Qtc 1.131 with a predicted F3 of 32.6 Hz, computed from Focal's published Thiele-Small parameters of Fs 30 Hz, Qts 0.78 and Vas 25 liters.
Two things worth stating plainly.
First, with a free-air Qts of 0.78, system Qtc cannot fall below 0.78 in any sealed enclosure regardless of volume. This driver is mildly underdamped in any sealed box, producing a modest lift near the corner frequency. That is the P 25 FSE's character, not a limitation of this cabinet. We build at 0.80 net because the returns flatten past that: going to a full cubic foot improves Qtc by only 0.03 and F3 by about 1 Hz.
Second, the figures above are computed from the T/S parameters Focal publishes, and they do not match the F3 values in Focal's suggested application table. Focal lists 37.5 Hz at 12 liters and 34 Hz at 18 liters. Running their own Qts and Vas through standard sealed box math at those volumes gives roughly 49 and 46 Hz instead. Notably, Focal's own published frequency response graph agrees with the computed figures rather than with their table, showing output rolling away below roughly 45 Hz. We publish what the driver data and the measured response both indicate.
Focal does publish driver displacement at 0.07 cubic feet, which many manufacturers in this category omit entirely, and it is accounted for in the net volume above.
Firing down into the floor, the sealed rolloff meets rising cabin gain below 60 Hz, and in-car response extends well below the anechoic figure.
Construction is the full Proline X Performance Optimized platform: ShopSabre CNC-cut Langboard Elite MDF with V-groove and dado joinery, perimeter cross-bracing, and a double-layer 1.5 inch front baffle (two 3/4 inch sheets bonded) for maximum baffle rigidity and driver isolation. Corners are square on Down Fire cabinets. The driver fires down into the floor with the terminal cup side mounted, keeping the connection accessible with the cabinet in place. Terminal cup is our Proline X ABS/carbon fiber composite pre-wired with 12 gauge OFC.
Bring your own Focal P 25 FSE. Single voice coil at 4 ohms nominal, so there is no wiring configuration to choose at the driver.
Manufactured in Tullahoma, Tennessee. 1-year enclosure warranty.
| Enclosure Type | Sealed | Down Fire Geometry | Floor-Coupled |
| Driver-Specific Fitment | Focal Flax Evo P 25 FSE (4Ω SVC) |
| Internal Volume (Gross) | 0.87 Cubic Feet |
| Internal Volume (Net After Displacement) | 0.80 Cubic Feet |
| Target System Qtc | 1.131 (Computed from Published T/S) |
| Predicted F3 | 32.6 Hz (Computed - See FAQ) |
| Driver Fs | 30 Hz |
| Driver Qts | 0.78 - Qtc Cannot Fall Below This In Any Sealed Box |
| Driver Qes / Qms | 0.95 / 5.0 |
| Driver Vas | 25 Liters / 0.883 Cubic Feet |
| Driver Mms | 190 g |
| Driver Cms | 0.15 mm/N |
| Driver BxL | 11.2 N/A |
| Driver Sd | 346 cm² |
| Driver Xmax | 11mm |
| Driver Rdc | 3.2 Ohms |
| Driver Displacement | 0.07 Cubic Feet / 2 Liters (Published by Focal) |
| Driver Sensitivity | 87 dB (2.83V/1m) |
| Driver Power Handling | 280 Watts RMS / 560 Watts Maximum |
| Driver Cone | Flax Fiber (Flax Evo) | Rubber Surround |
| Driver Voice Coil | 38mm / 1.5" | Glass Fiber Former | 4-Layer Copper |
| Driver Overall Diameter | 260mm / 10.24 Inches (Focal Spec) |
| Baffle Configuration | Down Firing - Driver Fires Toward Floor |
| Material | Langboard Elite 3/4" MDF |
| Front Baffle Construction | Double-Layer 1.5" MDF (Two 3/4" Sheets Bonded) |
| Joinery | V-Groove and Dado (CNC-Cut) |
| Corner Profile | Square (Down Fire Series Standard) |
| Construction | ShopSabre CNC / Perimeter Cross-Brace |
| External Width | 30 Inches |
| External Depth | 15 Inches |
| External Height | 6.125 Inches |
| Dimension Reference | All External Dimensions Measured In Down Fire Position |
| Voice Coil Configuration | Single Voice Coil | 4 Ohm Nominal |
| Mounting Hardware | 8/32 Threaded Inserts | Stainless Steel Machine Screws Included |
| Terminal Cup | Proline X ABS/Carbon Fiber Composite | Side Mounted | 12g OFC Pre-Wired |
| Damping | Polyfill Pre-Installed |
| Recommended Power | 200-280 Watts RMS (Focal Rated: 280W RMS) |
| Carpet Finish | Dark Gray Trunkliner (Standard) or Plush Black (+$10) |
| Bundle Options | Enclosure Only (Bring Your Own Focal P 25 FSE) |
| Warranty | 1-Year Limited (Enclosure) |
| Manufactured | Tullahoma, Tennessee, USA |
01Is it a sealed driver?
Efficiency bandwidth product places the motor before anything else is decided.
02What the box does to it
0.80 cu ft against a 25.0 L Vas.
03The watts that reach Xmax (in this enclosure)
Travel scales with the square root of power, so there is one wattage that puts the cone exactly on 11.0 mm — and a bigger one once a subsonic filter stops it wasting travel below the passband.
| Param | Value | Unit | Note |
|---|---|---|---|
| Fs | 30.00 | Hz | free-air resonance |
| Qts | 0.780 | SVC 4 | |
| Vas | 25.00 | L | equivalent compliance |
| Sd | 346.0 | cm² | effective piston area |
| Xmax | 11 | mm | one-way linear travel |
| Pe | 280 | W | continuous RMS |
| SPL | 80.4 | dB | 1 W / 1 m, derived from T/S |
Driver parameters as published by Focal FLAX EVO P 25 FSE technical sheet SCDB200217/2. Curves computed against this enclosure’s actual net airspace.
Built From a Spec Sheet, Not a Sales Sheet
Every Proline X Performance Series enclosure is CNC-cut from Langboard Elite MDF, 3/4" (18mm) panels produced to published mill specifications. Most enclosure manufacturers source generic MDF without published data. We can tell you the internal bond rating, the modulus of elasticity, the modulus of rupture, and the face and edge screw holding strength for every panel in this enclosure, because we chose the material based on those numbers, not on price or availability.
Langboard Elite is produced in the United States. The specifications below are pulled directly from Langboard's published mill data and are verifiable. This is the same panel stock used in our full Proline X lineup.
Langboard Elite MDF: Published Mill Data
| Property | Value | Why It Matters |
|---|---|---|
| Panel Stock | Langboard Elite MDF | Named, verifiable panel source, not generic "high-density MDF" |
| Thickness | 3/4" (18mm) | Industry standard for subwoofer enclosures; panels below this flex under pressure |
| Density | 48.5 lbs/ft³ | Higher density = less porosity, better screw retention, reduced resonance |
| Internal Bond | 200 psi | Measures resistance to delamination under sustained internal pressure. The most enclosure-relevant spec on this sheet |
| Modulus of Rupture (MOR) | 4,200 psi | Bending strength before the panel breaks, relevant for larger unsupported baffle spans |
| Modulus of Elasticity (MOE) | 410,000 psi | Stiffness under load; higher MOE means less panel flex under bass pressure, less resonance |
| Face Screw Holding | 325 lbs | How firmly the panel surface holds a screw; critical for baffle joint integrity over time |
| Edge Screw Holding | 250 lbs | Panel edge retention, relevant for every joint that isn't face-to-face |
200 psi: The Number That Actually Matters for Enclosures
The internal bond rating measures how well the MDF panel resists delamination under sustained pressure applied perpendicular to the face. In a subwoofer enclosure, every bass transient generates a pressure pulse that pushes outward on every panel simultaneously. A panel that begins to delaminate internally loses stiffness gradually. The symptoms are slow: a box that starts to sound softer, less defined, less punchy over months of use. 200 psi internal bond is the spec that determines how long this enclosure holds its acoustic integrity under daily use at real power levels.
410,000 psi MOE: Less Flex, Less Resonance
The modulus of elasticity measures panel stiffness, its resistance to bending under load. A stiffer panel flexes less under the pressure generated by a high-excursion driver at volume. Panel flex is a source of acoustic coloration: the panel itself begins to radiate sound at its own resonant frequency, adding distortion to the output. 410,000 psi stiffness combined with V-groove and dado joinery means the panels stay rigid and the bracing controls resonance at the structure level, not the panel level. The bass you hear comes from the driver, not the box.
325 lb Face / 250 lb Edge: Joints That Stay Locked
Screw holding strength determines how firmly the panel grips a fastener at the face and at the edge. This matters most at the baffle joint, where the front panel meets the side panels and where the driver is mounted. A panel with low screw holding strength allows fasteners to loosen over time under vibration, leading to air gaps at the joint and loss of acoustic seal. 325 lb face screw holding strength means the baffle hardware stays put. Combined with dado joinery and adhesive, the front panel on a Proline X Performance Series enclosure is not going anywhere.
Named Panel Stock: Not "Premium MDF"
The phrase "premium MDF" or "high-density MDF" appears on marketing copy for enclosures across every price point, from $40 to $400. It is not a specification. It is a description with no defined standard. Langboard Elite is a named, sourced, mill-documented product with published data. We name it in our copy because naming it holds us accountable to the spec. You can look up Langboard Elite independently, verify the numbers on this page, and confirm you are getting what we say you are getting. That is the point.
Why Proline X?
Most enclosures are built to a price point. Proline X is built to a spec. Every box starts with published-data MDF, gets CNC-cut to exact internal volume, and is assembled by hand in our Tennessee facility. The difference shows up in the measurements — and in how the box holds up two years into daily use.
CNC-Cut to Spec
Panels are machine-cut on ShopSabre CNC routers and joined with V-groove and dado joinery. Consistent geometry, no hand-cut variance, no gaps at the joints.
Handcrafted in USA
Hand-assembled at our facility in Tullahoma, TN. Every enclosure is inspected before it ships.
Tuned to the Build
Internal volume and port geometry are calculated to spec and CNC-cut to exact dimensions. The box performs the same way every time.
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