Proline X
Performance Optimized Down Fire Wide Sealed Dual 12" Enclosure | Morel Ultimo PowerSlim PS124D
SKU: PO 12D-S DFW PS
- Alignment: 0.807 cu ft net per chamber. Qtc 1.067, Fc 42.7 Hz, F3 32.7 Hz
- Down Fire Wide: 41"W x 14"D x 8.75"H in down fire position, excludes the 1.75" standoffs (installed height 10.5"). Stands lower than the standard 30 x 15 at 10.75"
- Height set by: airspace; 4.61" of clearance above the motor
- Chambers: Two fully separate sealed chambers, 3/4" MDF full divider, one shared side-mounted terminal cup
- Driver: Pair of Morel PS124D (DVC 4 ohm), 700W RMS each / 1400W combined, 24 Hz Fs, 11mm Xmax each way
- Build: Langboard Elite MDF, V-groove and dado, 1.5" double baffle with flush outer recess, full divider, 12g OFC side-mounted terminal cup
Financing available. Choose Shop Pay Installments at checkout.
Performance Optimized Down Fire Wide Sealed Dual 12" Enclosure | Morel Ultimo PowerSlim PS124D
More enclosures cut for Morel subwoofers: Morel Subwoofer Boxes
Proline X Performance Optimized Down Fire Wide Dual 12" Sealed
41 inch wide, 14 inch deep format. Cut for a pair of Morel Ultimo PowerSlim PS124D
The Down Fire Wide Format
Down Fire Wide is the Performance Optimized answer to a space that is long rather than deep or tall. This cabinet runs 41 inches wide by 14 inches deep by 8.75 inches tall: 1 inch shallower front to back than our standard 30 by 15 inch Down Fire platform, and 11 inches longer.
Fourteen inches is the practical minimum for a 12 inch driver: a 12 inch frame needs about 13 inches of baffle. Each PS124D's 12.008 inch frame sits on the 14 inch deep baffle with about 1.00 inch of baffle outside the flange fore and aft. Because the airspace is spread along 41 inches instead of 30, the wide cabinet usually stands lower than the standard box, and it does here: 8.75 inches against 10.75 inches for the standard 30 by 15 PS124D cabinet.
With the footprint fixed at 41 by 14, height is the free dimension, and it was solved to the airspace: 0.807 cubic feet net per chamber, against 0.80 in the standard box. The motor clears the top panel with 4.61 inches to spare, so clearance did not set the height.
Which one to choose. The standard 30 by 15 is the pick when length is limited. This one is the pick when height or depth is the limit and you have 41 inches of run: under or behind a rear bench, or along a cargo wall. Measure depth and height first; depth is usually the dimension that decides it.
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 cutouts, the mounting depth and the chamber volumes all come from the Morel Ultimo PowerSlim PS124D's own numbers. A Performance box fits your subwoofer. A Performance Optimized box was built for it.
Built Around a Pair of PS124D
The baffles are bored to the PS124D's 10.6 inch cutout, 268.6mm to Morel's spec, and the driver's 3.386 inch mounting depth leaves the motor well clear of the top panel.
The two numbers that matter most here are resonance and compliance. Fs is 24 Hz against a 49.4 liter Vas, and for a driver that mounts this shallow that pairing is unusual. Most shallow 12s sit in the low 30s for free-air resonance, which caps how low they go regardless of the box.
Each PS124D is a dual 4 ohm subwoofer rated 700 watts RMS with 2100 watts maximum transient handling. Flat honeycomb Hexatech aluminium cone, double magnet EVC motor, and a 129.5mm voice coil, 5.1 inches, wound in four layers of carbon on an aluminium former. Most shallow 12s run a 2 to 3 inch coil; nearly double the diameter gives far more surface area to shed heat. The Ultimo PowerSlim series took the EISA Best In-Car Subwoofer award for 2023-2024.
Net Volume, Not Gross
Total gross volume is 1.81 cubic feet, split by the divider into two chambers. After the brace and an estimated 0.08 cubic feet of displacement (Morel publishes no displacement figure, so the 12 inch rule of thumb is used) per driver, each chamber holds 0.807 cubic feet net, 1.615 cubic feet net total.
True net, not marketing net. Internal volume is calculated from the machined cavity dimensions and the driver's displacement, not estimated from external dimensions minus wall thickness.
That produces Qtc 1.067 with Fc at 42.7 Hz and a predicted F3 of 32.7 Hz per driver, computed from Morel's published Fs 24 Hz, Qts 0.6 and Vas 49.4 liters.
Each chamber matches Morel's own sealed recommendation of 22.7 liters, so each driver sees the alignment Morel designed for. Qts is 0.6, so system Qtc cannot fall below that in any sealed enclosure; at Qtc 1.067 the alignment carries a modest lift near the corner frequency, which is the driver's intended character.
These figures are anechoic. Firing down into the floor, the sealed rolloff meets rising cabin gain below about 60 Hz, so in-car response extends below the published F3.
Two Chambers, Not One
This enclosure follows the Proline X standing design rule for dual sealed builds: two fully separate chambers divided by a bonded full-height 3/4 inch MDF panel.
Two drivers sharing one sealed volume interact acoustically. Each driver's compression phase becomes the pressure environment the other is working against, which smears transient response and blurs the alignment each would have on its own. A full divider eliminates that. Each PS124D gets its own 0.807 cubic feet net and its own polyfill.
On a long cabinet the divider does structural work as well, tying the front and rear walls together at the centre of the 41 inch span.
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 both chambers airtight under sustained pressure cycling. Corners are square on Down Fire cabinets.
The cabinet measures 41 inches wide by 14 inches deep by 8.75 inches tall, measured in the down fire position, excluding the feet. The 1.75 inch standoffs ship with the enclosure but are not installed, so the installed height is 10.5 inches. Plan the space around that figure.
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, with 8/32 threaded inserts at each driver position, stainless machine screws included.
Round Frame, 14 Inch Baffle
The 10.6 inch cutouts sit side by side along the 41 inch length on the 14 inch deep baffle, leaving about 1.00 inch of baffle outside the flange fore and aft. No rotation or special layout is needed for a round frame.
Separate Chambers
A bonded full-height 3/4 inch divider gives each driver its own 0.807 cubic feet and its own light polyfill wall lining, and ties the walls together mid span.
One Shared 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 to both driver positions in parallel.
Power and Wiring
Morel rates each PS124D at 700 watts RMS with 2100 watts maximum transient handling, and publishes a recommended range of 350 to 700 watts RMS per driver. Combined that is 1400 watts RMS, which asks for a serious amplifier.
One side mounted terminal cup serves both chambers, pre-wired in 12 gauge OFC to both driver positions in parallel. Each driver carries dual 4 ohm coils, so final impedance is set at the drivers. Wire both identically, since mismatched wiring between chambers splits power unevenly, and confirm the resulting load against your amplifier's minimum stable impedance.
Bring your own pair of Morel Ultimo PowerSlim PS124D; the drivers are purchased separately. The enclosure carries a 1 year limited warranty.
Cut for the Driver, Not the Catalog
We cut every Down Fire Wide cabinet to one driver's published cutout, mounting depth and airspace, then build it one at a time in Tullahoma, Tennessee. Questions on fitment or amplifier matching, call 931-563-5151.
| Series | Proline X Performance Optimized Down Fire Wide |
| Compatible Driver | Morel Ultimo PowerSlim PS124D (DVC 4 ohm), pair required. Direct fit |
| Enclosure Type | Sealed, dual driver, down fire, floor coupled |
| Intended Fitment | Long, low spaces where height or depth is the limit and 41 in of run is available |
| Firing Direction | Down firing. Feet ship uninstalled, so front or up firing is also possible |
| Chamber Configuration | Two fully separate chambers, full divider, single shared side-mounted terminal cup |
| External Width | 41 in |
| External Depth | 14 in |
| External Height | 8.75 in in the down fire position, excludes standoffs |
| Installed Height | 10.5 in including the 1.75 in standoffs |
| Dimension Reference | All external dimensions measured in down fire position |
| Standard 30 x 15 Version | 10.75 in tall, 0.80 cu ft net per chamber |
| Internal Volume, Gross | 1.81 cu ft total |
| Per-Chamber Net Volume | 0.807 cu ft after displacement |
| Total Net Volume | 1.615 cu ft |
| Height Set By | Airspace; 4.61 in clearance above the motor |
| Alignment (per chamber) | Qtc 1.067, Fc 42.7 Hz, F3 32.7 Hz anechoic |
| Woofer Opening | 10.6 in each |
| Mounting Depth Required | 3.386 in |
| Frame Outer Diameter | 12.008 in |
| Driver Displacement | 0.08 cu ft, estimated; Morel publishes no displacement figure, so the 12 inch rule of thumb is used |
| Driver Fs | 24 Hz |
| Driver Qts | 0.6 |
| Driver Vas | 49.4 Liters Each |
| Driver Xmax | ±11mm |
| Cone Area | 452.4 cm² Each / 904.8 cm² Total |
| Power Handling | 700 Watts RMS Each / 1400 Watts RMS Combined |
| Driver Cone | Flat Honeycomb Hexatech Aluminium |
| Driver Voice Coil | 129.5mm / 5.1" | 4 Layers Carbon | Aluminium Former |
| Driver Motor | Double Magnet EVC |
| Awards | EISA Best In-Car Subwoofer 2023-2024 (Ultimo PowerSlim Series) |
| Driver Mounting | 8/32 Threaded Inserts | Stainless Steel Machine Screws Included | 2 Sets |
| Voice Coil Configuration | Dual 4-Ohm Per Driver - Final Impedance Set At The Drivers |
| Recommended Power Per Driver | 350-700 Watts RMS (Morel Rated Range) |
| Material | Langboard Elite 3/4 in MDF |
| Joinery | V-groove and dado, CNC cut on ShopSabre routers |
| Front Baffle | 1.5 in double baffle, outer layer machined as a flush recess |
| Internal Bracing | Full-height 3/4 in bonded divider plus perimeter cross-brace |
| Corner Profile | Square (Down Fire series standard) |
| Terminal Cup | One Proline X ABS and carbon fiber composite, side mounted, pre-wired 12 gauge OFC to both driver positions |
| Standoffs | 1.75 in, included, shipped uninstalled |
| Damping | Polyfill installed as a light wall lining in each chamber |
| Carpet | Plush black |
| Bundle Options | Enclosure only (bring your own pair of Morel PS124D) |
| Warranty | 1 year limited (enclosure) |
| Built In | 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
0.807 cu ft against a 49.4 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 | 24.00 | Hz | free-air resonance |
| Qts | 0.600 | D4 | |
| Vas | 49.40 | L | equivalent compliance |
| Sd | 452.4 | cm² | effective piston area |
| Xmax | 11 | mm | one-way linear travel |
| Pe | 700 | W | continuous RMS |
| SPL | 81.7 | dB | 1 W / 1 m, derived from T/S |
Driver parameters as published by Morel Ultimo PowerSlim owner's manual, rev 24-12-23. 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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