Proline X
Performance Optimized Down Fire Wide Sealed 10" Enclosure | Morel Ultimo PowerSlim PS104D
SKU: PO 10-S DFW PS
- Alignment: 0.500 cu ft net. Qtc 1.164, Fc 48.4 Hz, F3 35.9 Hz
- Down Fire Wide: 41"W x 12"D x 4.625"H in down fire position, 3" shallower and 11" longer than the standard 30 x 15, for under rear seats and narrow cargo floors
- Driver: Morel Ultimo PowerSlim PS104D, DVC 4 ohm, 700W RMS / 1800W max, 11mm Xmax each way, 3.1" mounting depth
- Build: Windowed U-brace, 1.5" double baffle, one side-mounted terminal cup, 12g OFC
- Feet: 1.75", ship uninstalled. Installed height 6.375"
Financing available. Choose Shop Pay Installments at checkout.
Performance Optimized Down Fire Wide Sealed 10" Enclosure | Morel Ultimo PowerSlim PS104D
More enclosures cut for Morel subwoofers: Morel Subwoofer Boxes
Proline X Performance Optimized Down Fire Wide 10" Sealed
Under rear seat and narrow cargo floor fitment. Cut for the Morel Ultimo PowerSlim PS104D
The Down Fire Wide Format
Down Fire Wide answers a specific space problem. The floor under the rear seat of a truck or SUV, and many narrow cargo floors, is long and shallow, and a standard 30 by 15 inch enclosure will not go in it.
So the cabinet is turned sideways. This one runs 41 inches wide by 12 inches deep by 4.625 inches tall, measured in the down fire position. Against our standard 30 by 15 inch PowerSlim cabinet it takes the same PS104D driver, sits 3 inches shallower front to back and runs 11 inches longer. The airspace lost from the depth is recovered along the length, so the driver still gets a properly sized chamber rather than a compromised one.
Which one to choose. If you have 15 inches of depth, the standard 30 by 15 cabinet is the pick: it is shorter end to end and easier to place. Choose this one when depth is the limiting dimension and you have 41 inches of run. Measure the depth first; under seat spaces vary widely between cab configurations.
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 mounting depth and the chamber volume all come from the Morel Ultimo PowerSlim PS104D's own numbers. A Performance box fits your subwoofer. A Performance Optimized box was built for it.
Built Around the Morel PS104D
The baffle is bored to the PS104D's 9.1 inch cutout, 231.5mm to Morel's spec, and the internal height starts from the driver's 3.1 inch mounting depth. The frame is round and sits on the 12 inch deep baffle with material to spare.
Each PS104D is a dual 4 ohm voice coil driver rated 700 watts RMS with 1800 watts maximum transient handling, working 346.4 square centimeters of cone with 11mm of Xmax in each direction. Free-air resonance is 29.1 Hz against a 25 liter Vas, and the motor is a double magnet EVC system behind a flat honeycomb Hexatech aluminium cone.
What lets it take that much power in 3.1 inches of depth is the voice coil. Morel winds a 129.5mm coil, 5.1 inches, in four layers of carbon on an aluminium former. Most shallow 10s run a 2 to 2.5 inch coil, so this is more than twice the diameter and far more surface area to shed heat. The Ultimo PowerSlim series took the EISA Best In-Car Subwoofer award for 2023-2024.
Net Volume and Alignment
The chamber holds 0.500 cubic feet net, from 0.556 cubic feet gross after 0.05 cubic feet of estimated driver displacement (Morel publishes none).
Computed from the driver's published Thiele-Small parameters, that produces Qtc 1.164 with Fc at 48.4 Hz and a predicted F3 of 35.9 Hz.
Height is the free dimension. With the footprint fixed at 41 by 12, the cabinet height was solved to put the chamber on the same airspace as the standard 30 by 15 box, then rounded up to the next sixteenth so the volume lands on the target rather than under it. The motor clears the top panel with 0.78 inches to spare, so airspace set this height, not clearance.
That is Morel's own sealed recommendation of 12.7 liters. Qts is 0.7, so system Qtc cannot fall below 0.7 in any sealed enclosure regardless of volume. The alignment here sits above unity with a lift near the corner frequency. That is the driver's intended character, and Morel built its volume recommendation around it.
True net, not marketing net. Internal volume is calculated from the machined cavity dimensions and the driver displacement, not estimated from external dimensions minus wall thickness. All figures are anechoic; firing down into the floor, the sealed rolloff meets rising cabin gain below 60 Hz and in-car response extends well 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.
The cabinet measures 41 inches wide by 12 inches deep by 4.625 inches tall, measured in the down fire position. The 1.75 inch feet ship with the enclosure but are not installed, so plan the space around an installed height of 6.375 inches if you use them.
1.5 Inch Double Baffle
Two 3/4 inch layers laminated to 1.5 inches, with the outer layer machined as a flush recess so the driver bolts to the inner layer on 8/32 threaded inserts. Stainless machine screws included.
Windowed U-Brace
A windowed U-brace dadoed to the shell ties the long 41 inch panels together without closing off the chamber. Polyfill is installed as a light wall lining.
Side-Mounted Terminal Cup
One 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
Morel rates the PS104D at 700 watts RMS with 1800 watts maximum transient handling, and publishes a recommended range of 350 to 700 watts RMS. Set gains inside that range.
The coils are dual 4 ohm, so you set the final load at the driver: two coils in parallel for 2 ohms, in series for 8 ohms. One side mounted terminal cup, pre-wired in 12 gauge OFC. Confirm your amplifier is stable at the load you choose.
Bring your own Morel Ultimo PowerSlim PS104D; the driver is purchased separately. The enclosure carries a 1 year limited warranty. Plush black carpet.
Cut for the Driver, Not the Catalog
Down Fire Wide, built for the space under a rear bench, 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 PS104D (DVC 4 ohm). Direct fit |
| Enclosure Type | Sealed, single driver, down fire, floor coupled |
| Intended Fitment | Under the rear seat of trucks and SUVs and narrow cargo floors, where depth is the limiting dimension |
| Firing Direction | Down firing, driver fires toward the floor. Feet ship uninstalled, so front or up firing is also possible |
| Chamber Configuration | Single sealed chamber, windowed U-brace, one side-mounted terminal cup |
| External Width | 41 in |
| External Depth | 12 in |
| External Height | 4.625 in in the down fire position, excludes feet |
| Installed Height | 6.375 in with the 1.75 in feet |
| Standard 30 x 15 Equivalent | 30 x 15 x 4.9375 in, 0.50 cu ft net. Same driver, deeper and shorter footprint |
| Internal Volume, Gross | 0.556 cu ft |
| Net Volume | 0.500 cu ft after displacement |
| Height Set By | Airspace; motor clearance allows a lower cabinet |
| Clearance Above Motor | 0.78 in |
| Alignment | Qtc 1.164, Fc 48.4 Hz, F3 35.9 Hz anechoic |
| Woofer Opening | 9.1 in / 231.5mm, Morel spec |
| Mounting Depth Required | 3.1 in / 79.6mm, Morel spec |
| Driver Overall Diameter | 10.35 in / 263mm, Morel spec |
| Driver Fs | 29.1 Hz |
| Driver Qts | 0.7; Qtc cannot fall below this in any sealed box |
| Driver Qes / Qms | 0.9 / 3.6 |
| Driver Vas | 25 L |
| Driver Mms / BL | 203 g / 8.1 |
| Driver Sd | 346.4 cm2 |
| Driver Xmax | 11mm each way |
| Driver Sensitivity | 82 dB (2.83V/1m) |
| Driver Voice Coil | 129.5mm / 5.1 in, four layers carbon, aluminium former |
| Driver Motor | Double magnet EVC |
| Driver Cone | Flat honeycomb Hexatech aluminium |
| Morel Sealed Recommendation | 12.7 liters per driver |
| Driver Power Handling | 700 W RMS / 1800 W max transient |
| Recommended Power | 350 to 700 W RMS, Morel rated range |
| Voice Coil Configuration | Dual 4 ohm: 2 ohm parallel or 8 ohm series at the driver |
| Driver Displacement | 0.05 cu ft, estimated; Morel publishes none |
| Material | Langboard Elite MDF |
| Construction | CNC cut on ShopSabre routers, V-groove and dado joinery |
| Panel Thickness | 0.75 in |
| Front Baffle | 1.5 in double baffle, outer layer machined as a flush recess |
| Internal Bracing | Windowed U-brace, dadoed to the shell |
| Corner Profile | Square, Down Fire series standard |
| Driver Mounting | 8/32 threaded inserts, stainless machine screws included |
| Terminal Cup | One Proline X ABS and carbon fiber composite, side mounted |
| Internal Wiring | 12 gauge OFC |
| Feet | Included, 1.75 in, shipped uninstalled |
| Damping | Polyfill pre-installed as a light wall lining |
| Carpet | Plush Black |
| Bundle Options | Enclosure only, bring your own Morel PS104D |
| 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
0.500 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 in this alignment a subsonic filter barely moves it.
| Param | Value | Unit | Note |
|---|---|---|---|
| Fs | 29.10 | Hz | free-air resonance |
| Qts | 0.700 | D4 | |
| Vas | 25.00 | L | equivalent compliance |
| Sd | 346.4 | cm² | effective piston area |
| Xmax | 11 | mm | one-way linear travel |
| Pe | 700 | W | continuous RMS |
| SPL | 80.2 | 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.
Shop By Series
