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
Proline X Performance Optimized Down Fire 10" Sealed
Cut and tuned for the Focal Flax Evo P 25 FSE
Performance, Performance Optimized, and Micro
Proline X builds three tiers of Down Fire enclosure. The difference is not finish or materials, it is whether the cabinet was designed for a category or for a driver, and how much of the fitting work is already done for you.
| Performance | Performance Optimized | Micro Series | |
|---|---|---|---|
| Fitment | Universal. Accepts any subwoofer that clears the published cutout and mounting depth. | Woofer specific. Cut for one named subwoofer, with cutout, mounting depth, magnet clearance and displacement drawn in CAD from that driver. | Woofer specific. Cut for one named subwoofer. |
| Footprint | Sized to the driver diameter. 24.5 by 13.5 inches on the 10 inch. | Shared 30 by 15 inch platform on most builds, with cabinet height as the variable. A few drivers need a wider or deeper platform. | Compact per driver footprint. 21.5 by 14.5 inches on the 10 inch. |
| Front baffle | Single, 3/4 inch. | Double, 1.5 inch, outer layer machined as a flush recess. | Double, 1.5 inch. |
| Driver mounting | Solid flange. You drill your own mounting holes. | 8/32 threaded inserts, stainless machine screws included. | 8/32 threaded inserts, stainless machine screws included. |
| Joinery | V-groove and dado, CNC cut. | V-groove and dado, CNC cut, perimeter cross brace. | Stack fab, dowel reinforced. |
| Published alignment | Modeled Qtc profiles across a range of drivers. No single response curve. | A real predicted Qtc and F3 for that exact driver, calculated from its own Thiele-Small parameters. | Target alignment described in the listing. |
| Carpet | Gray standard, black optional. | Plush black. | Plush black. |
| Warranty | 1 year limited. | 1 year limited. | 2 years. |
Feet ship with every tier, uninstalled on purpose. Mount them where your floor wants them for a down fire install, or leave them off and run the cabinet front firing or up firing. The orientation is yours to choose.
This page is a Performance Optimized enclosure. The airspace, the cutout and the cabinet height all come from the Focal Flax Evo P 25 FSE's own published numbers. A Performance box fits your subwoofer. A Performance Optimized box was built for it.
Built Around the Focal P 25 FSE
The baffle is bored for the P 25 FSE's 260mm, 10.24 inch frame and the cavity is machined to 0.80 cubic feet net around it. The finished cabinet stands 6.125 inches tall on a 30 by 15 inch footprint, measured in the down fire position, which fits under seats and in cargo wells that will not accept a conventional box.
The P 25 FSE is a 4 ohm single voice coil driver rated 280 watts RMS and 560 watts maximum, with 11mm of Xmax across 346 cm² of cone area. The construction is what separates Focal from the rest of this category: a flax fiber cone in their Flax Evo layup, a rubber surround, and a 38mm four-layer copper voice coil on a glass fiber former.
Flax is Focal's alternative to the polypropylene and treated paper used elsewhere in this class. The appeal is stiffness relative to mass combined with good internal damping, which helps a cone hold its shape under load without ringing. Focal has been refining the material across their range for years, and Flax Evo is the current version of it.
Net Volume, Not Gross
The machined cavity measures 0.87 cubic feet gross. Focal publishes driver displacement at 0.07 cubic feet, which many manufacturers in this category omit entirely, so the net figure here is subtracted rather than estimated. The working airspace is 0.80 cubic feet net.
True net, not marketing net. Internal volume is calculated from the machined cavity dimensions and the driver's published displacement, not estimated from external dimensions minus wall thickness.
Building larger changes very little. The driver's free-air Qts is 0.78, and system Qtc can never fall below the driver's Qts in any sealed enclosure, so this one is mildly underdamped no matter what you build. At 0.80 net it lands at Qtc 1.131 with F3 at 32.6 Hz, which produces a modest lift near the corner frequency. Going to a full cubic foot buys roughly one hertz of extension, which does not justify the extra cabinet height on an enclosure designed to fit under a seat. This driver is single voice coil, so there is no coil variant to choose between and no wiring decision at the driver.
Where Focal's Published Numbers Disagree
The alignment figures above are computed from the Thiele-Small parameters Focal publishes, Fs 30 Hz, Qts 0.78 and Vas 25 liters. They do not match the F3 values in Focal's suggested application table. That table lists 37.5 Hz at 12 liters and 34 Hz at 18 liters. Running Focal's own Qts and Vas through standard sealed box math at those same volumes gives roughly 49 and 46 Hz instead.
The deciding evidence is on the same technical sheet. Focal's own published frequency response graph agrees with the computed figures rather than with the application table, showing output rolling away below roughly 45 Hz. Two of Focal's three data sources agree with each other and only the application table is the outlier, so we publish what the driver data and the measured response both indicate.
Down Fire Construction
Cut with V-groove and dado joinery on our ShopSabre routers from Langboard Elite 3/4 inch MDF, a dense 48.5 lb/ft³ board with a 200 psi internal bond and 410,000 psi MOE. Every panel joint is a machined interlocking groove that mechanically locks before adhesive is applied, which keeps the cabinet airtight under sustained pressure cycling. Corners are square on Down Fire cabinets.
Double Baffle, Flush Recess
The front baffle is 1.5 inches, two bonded 3/4 inch sheets, with the outer layer machined as a flush recess so the driver bolts to the inner layer. That recovers 3/4 inch of internal clearance.
Side-Mounted Terminal Cup
Proline X ABS and carbon fiber composite cup with stainless hardware and copper ring terminals, pre-wired in 12 gauge OFC. Side mounted so it stays accessible with the baffle facing the floor.
Single Cup, 4 Ohm Load
One side mounted cup, pre-wired in 12 gauge OFC, presenting the driver's 4 ohm nominal load straight to the amplifier. No series or parallel decision to make. A perimeter cross-brace ties the long spans together and polyfill is pre-installed.
Power and Warranty
Focal rates the P 25 FSE at 280 watts RMS with 560 watts maximum. Target 200 to 280 watts RMS of clean, unclipped power. Confirm your amplifier is comfortable at a 4 ohm load and set your gain to the 280 watt rating.
Drivers mount to 8/32 threaded inserts with stainless machine screws, included. The enclosure carries a 1 year limited warranty. Bring your own Focal Flax Evo P 25 FSE; the driver is purchased separately.
Cut for the Driver, Not the Catalog
One driver, one volume, one set of machine files. Cut, assembled and inspected one at a time in Tullahoma, Tennessee.
| Series | Proline X Performance Optimized Down Fire |
| Driver-Specific Fitment | Focal Flax Evo P 25 FSE (4Ω SVC) |
| Enclosure Type | Sealed | Down Fire Geometry | Floor-Coupled |
| Baffle Configuration | Down Firing - Driver Fires Toward Floor |
| External Width | 30 Inches |
| External Depth | 15 Inches |
| External Height | 6.125 Inches |
| Dimension Reference | All External Dimensions Measured In Down Fire Position |
| 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) |
| Voice Coil Configuration | Single Voice Coil | 4 Ohm Nominal |
| Material | Langboard Elite 3/4" MDF |
| Construction | ShopSabre CNC / Perimeter Cross-Brace |
| Joinery | V-Groove and Dado (CNC-Cut) |
| Front Baffle Construction | Double-Layer 1.5" MDF (Two 3/4" Sheets Bonded) |
| Corner Profile | Square (Down Fire Series Standard) |
| 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 | Plush Black |
| 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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