Proline X
Performance Optimized Down Fire Wide Sealed 10" Enclosure | Focal SUB 25 KXE
SKU: PO 10-S DFW KXE
- Alignment: 1.300 cu ft net, Qtc 0.646, Fc 47.2 Hz, F3 52.1 Hz; height set by the motor, not the airspace
- Down Fire Wide: 41"W x 12"D x 8.3125"H, excludes standoffs, 3 in shallower than the standard 30 x 15
- Driver: Focal SUB 25 KXE, 600 W RMS, 22.5 mm Xmax, 6.77 in mounting depth
- Standoffs: Included, 1.75 in, shipped uninstalled. Installed height 10.0625 in
Financing available. Choose Shop Pay Installments at checkout.
Performance Optimized Down Fire Wide Sealed 10" Enclosure | Focal SUB 25 KXE
More enclosures cut for Focal subwoofers: Focal Subwoofer Boxes
Proline X Performance Optimized Down Fire Wide 10" Sealed
Under rear seat fitment for trucks and SUVs. Cut for the Focal SUB 25 KXE
The Down Fire Wide Format
Down Fire Wide is the Performance Optimized answer to a specific problem: the space under the rear seat of a truck or SUV, or a narrow cargo floor, is long and shallow, and the standard 30 by 15 inch Down Fire cabinet will not go in it.
This cabinet takes the same Focal SUB 25 KXE and turns the footprint sideways. It runs 41 inches wide by 12 inches deep by 8.3125 inches tall: 3 inches shallower front to back than the standard 30 x 15 cabinet and 11 inches longer. The airspace given up in depth is recovered along the length.
Which one to choose. If you have 15 inches of depth, the standard 30 x 15 Focal SUB 25 KXE enclosure is the pick. Choose Down Fire Wide when depth is the limit: under a rear bench or on a narrow cargo floor, with at least 12 inches of depth and 41 inches of run.
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. Down Fire Wide variants like this one run long and shallow for under seat fitment. | Compact per driver footprint. 21.5 by 14.5 inches on the 10 inch. |
| Front baffle | Single, 3/4 inch. | Double layer, outer layer machined as a flush recess. 1.5 inch. | 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 cutout, the cabinet height and the airspace all come from the Focal SUB 25 KXE's own published numbers. A Performance box fits your subwoofer. A Performance Optimized box was built for it.
Built Around the Focal SUB 25 KXE
The baffle is cut to 9.30 in (236 mm). Loudspeaker Database lists a 235 mm cutout, but Focal's own drawing puts the basket at 235.2 mm just under the flange, which a 235 mm hole would not pass; the 236 mm cut clears it and the 10.55 inch (268 mm) frame still covers it with margin. That frame sits on the 12 inch deep baffle.
The SUB 25 KXE is the 10 inch of Focal's K2 Power line: an aramid-fiber K2 sandwich cone on a butyl surround, a 65 mm dual 4 ohm voice coil, rated 600 watts RMS and 1200 watts maximum, with 22.5 mm of one-way excursion. It is 6.77 inches deep, which matters on a down fire, where the motor rises into the cabinet.
Every figure comes from Focal's own SUB 25 KXE technical sheet. One number on it is soft: Focal prints 20 liters of Vas, but the published moving mass and resonance imply nearer 16 liters. If that is the truer figure, the Qtc on this page reads a few hundredths lower, so treat it as a range a few hundredths wide.
Focal does not publish a position on down firing this driver, and this cabinet makes no claim on their behalf. The standoffs ship uninstalled, so front or up firing remains your choice at install time.
Net Volume and Alignment
This cabinet holds 1.300 cubic feet net, from 1.418 gross, after the driver's 0.11 cubic feet of displacement.
Computed from Focal's published Fs 38 Hz, Qts 0.52 and Vas 20 liters, that produces Qtc 0.646 with Fc at 47.2 Hz and a predicted F3 of 52.1 Hz.
Height here is set by the driver, not the airspace. The 6.77 inch mounting depth puts the motor far enough into the cabinet that the height is fixed by motor clearance, 0.75 inch above the motor. At 8.3125 inches tall the wide box holds 1.300 cubic feet net, more than the 1.18 cubic feet the standard 30 x 15 box was built to. More air lowers Qtc, which is the safe direction: a slightly more damped alignment with a gentler rolloff.
Below 0.707 the rolloff is gentle and F3 sits above Fc, which is what a slightly over-damped sealed box does. It is a clearance fact, not a tuning choice.
These are anechoic figures. Firing down into the floor, the sealed rolloff meets rising cabin gain, so in-car response extends below them.
Down Fire Wide 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, no radii. Polyfill is installed as a light wall lining, finished in plush black carpet.
The cabinet measures 41 inches wide by 12 inches deep by 8.3125 inches tall, measured in the down fire position, excluding standoffs. The 1.75 inch standoffs ship with the enclosure but are not installed. Fitted, the installed height is 10.0625 inches, so plan the space around that stack.
1.5 Inch Double Baffle
Two 3/4 inch layers laminated to 1.5 inches, the outer layer machined as a flush recess so the driver bolts to the inner layer. Focal prints no bolt circle, so the baffle ships undrilled with a threaded insert kit and stainless machine screws.
Standoffs Included
Focal publishes no front clearance figure, so this cabinet uses the Proline X standard 1.75 inch standoff, shipped uninstalled. At that height the floor slot is 1.01 times the cone area, the minimum for the KXE's long excursion.
Windowed U-Brace
A windowed U-brace ties the long top and bottom panels together across the 41 inch span without walling off the airspace.
Side-Mounted Terminal Cup
Proline X ABS and carbon fiber composite cup with stainless hardware and copper ring terminals, side mounted and pre-wired in 12 gauge OFC, so it stays accessible with the baffle facing the floor.
Power and Wiring
Focal rates the SUB 25 KXE at 600 watts RMS and 1200 watts maximum. Target 420 to 600 watts RMS at the final load.
The SUB 25 KXE carries two 4 ohm voice coils (3.2 ohms DC each): wire them in parallel for a nominal 2 ohm load or in series for 8 ohms. Confirm the load against your amplifier's minimum stable impedance before powering the system.
Focal's drawing shows eight mounting holes but prints no bolt circle, so the baffle ships undrilled with a threaded insert kit: set the driver in the recess, mark its holes, drill, press the inserts and bolt it down.
Bring your own SUB 25 KXE; the driver is purchased separately. The enclosure carries a 1 year limited warranty. Questions on fitment or amplifier matching, call 931-563-5151.
Cut for the Driver, Not the Catalog
Down Fire Wide, built for the space under a rear bench. We build every one to order in Tullahoma, Tennessee.
| Specification | Value |
|---|---|
| Series | Proline X Performance Optimized Down Fire Wide |
| Compatible Driver | Focal SUB 25 KXE (K2 Power), quantity 1. Direct fit |
| Enclosure Type | Sealed, down fire, floor coupled |
| Intended Fitment | Under the rear seat of trucks and SUVs, or narrow cargo floors, where depth is the limiting dimension |
| Chamber Configuration | Single chamber, windowed U-brace, one side-mounted terminal cup |
| External Width | 41 in |
| External Depth | 12 in |
| External Height | 8.3125 in, measured in down fire position, excludes standoffs |
| Installed Height | 10.0625 in with the 1.75 in standoffs fitted |
| Internal Volume, Gross | 1.418 cu ft |
| Internal Volume, Net Acoustic | 1.300 cu ft after displacement |
| Alignment | Qtc 0.646, Fc 47.2 Hz, F3 52.1 Hz anechoic |
| Height Set By | Driver clearance: 0.79 in above the motor |
| Comparison, Standard Down Fire | 30 x 15 x 8.27 in, 1.18 cu ft net |
| Woofer Opening | 9.30 in (236 mm); clears the 235.2 mm basket on Focal's drawing |
| Frame Outer Diameter | 10.55 in (268 mm), Focal drawing |
| Driver Mounting Depth | 6.77 in required |
| Floor Slot | 1.01 times the cone area at the 1.75 in standoff |
| Bolt Circle | Not printed by Focal; threaded insert kit included |
| Fs / Qts / Qes / Qms | 38 Hz / 0.52 / 0.58 / 5.0 |
| Vas / Mms / Cms / Bl | 20 L / 163 g / 0.12 mm/N / 21.5 N/A |
| Driver Sd | 327 cm², published by Focal |
| Xmax | 22.5 mm one way, Focal spec |
| DC Resistance | 3.2 + 3.2 ohm (6.4 ohm in series) |
| Driver Sensitivity | 84.5 dB at 2.83 V / 1 m, Focal spec |
| Driver Power Handling | 600 W RMS / 1200 W maximum per driver |
| Voice Coil | 65 mm dual 4 ohm, CCAW on a glass fiber former, 4 layers |
| Parameter Source | Focal SUB 25 KXE technical sheet, v1 29/09/2023 |
| Wiring Options | Dual 4 ohm coils: 2 ohm in parallel, 8 ohm in series |
| Driver Displacement | 3 L / 0.11 cu ft, published by Focal |
| Material | Langboard Elite 3/4 in MDF |
| Construction | ShopSabre CNC cut, V-groove and dado joinery, windowed U-brace |
| Front Baffle | 1.5 in double baffle, outer layer machined as a flush recess |
| Corner Profile | Square, Down Fire series standard |
| Driver Mounting | Threaded insert kit included, NOT pre-installed: Focal prints no bolt circle |
| Terminal Cup | One Proline X ABS and carbon fiber composite, side mounted |
| Internal Wiring | 12 gauge OFC |
| Damping | Polyfill installed, light wall lining |
| Standoffs | 1.75 in, included, shipped uninstalled |
| Carpet | Plush black |
| Warranty | 1 Year Limited |
| Built In | Tullahoma, Tennessee |
01Is it a sealed driver?
Efficiency bandwidth product places the motor before anything else is decided.
02What the box does to it
1.300 cu ft against a 20.0 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 22.5 mm — and a bigger one once a subsonic filter stops it wasting travel below the passband.
| Param | Value | Unit | Note |
|---|---|---|---|
| Fs | 38.00 | Hz | free-air resonance |
| Qts | 0.520 | dual 4 ohm, coils in series | |
| Vas | 20.00 | L | equivalent compliance |
| Sd | 327.0 | cm² | effective piston area |
| Xmax | 22.5 | mm | one-way linear travel |
| Pe | 600 | W | continuous RMS |
| SPL | 84.6 | dB | 1 W / 1 m, derived from T/S |
Driver parameters as published by Focal SUB 25 KXE technical sheet. 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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