Proline X
Performance Optimized Down Fire Sealed Dual 12" Enclosure | Morel Ultimo PowerSlim PS124D
SKU: PO 12D-S DF PS
- Alignment: 0.80 cu ft net per chamber - Morel's own spec. Qtc 1.070, F3 34.2 Hz per driver - deepest in the Down Fire line
- Chambers: Two fully separate sealed chambers, 3/4" MDF full divider, one shared side-mounted terminal cup
- Drivers: Pair of Morel PS124D (DVC 4Ω), 700W RMS each / 1400W combined, 24 Hz Fs, ±11mm Xmax
- Cabinet: 30"W x 15"D x 10.75"H measured in down fire position, square corners
Financing available — choose Shop Pay Installments at checkout.
Performance Optimized Down Fire Sealed Dual 12" Enclosure | Morel Ultimo PowerSlim PS124D
Proline X PO Down Fire Dual 12" Sealed
Cut and tuned for a pair of Morel Ultimo PowerSlim PS124D
Built Around a Pair of PS124D
Nothing about this cabinet is generic. Both baffles are bored to the PS124D's 10.6 inch cutout, 268.6mm to Morel's spec, and the internal height of each chamber is set by the driver's 3.4 inch mounting depth and the volume it needs. This is the deepest reaching cabinet in the Proline X Down Fire line, and it does it twice.
The reason is the driver's 24 Hz free-air resonance against a 49.4 liter Vas. In a 3.4 inch mounting depth those are conventional driver numbers rather than shallow driver numbers, and most shallow 12s sit in the low 30s for free-air resonance, which caps how low they go regardless of the box. Here it produces a predicted F3 of 34.2 Hz per driver.
Each PS124D is a dual 4 ohm voice coil subwoofer rated 700 watts RMS with 2100 watts maximum transient handling, so the pair carries 1400 watts RMS combined across 904.8 square centimeters of cone. Flat honeycomb Hexatech aluminium cones, double magnet EVC motors, and 129.5mm voice coils, 5.1 inches, wound in four layers of carbon on aluminium formers. Most shallow 12s run a 2 to 3 inch coil, and that surface area difference is what sets the continuous rating. The Ultimo PowerSlim series took the EISA Best In-Car Subwoofer award for 2023-2024.
Two Chambers, Not One Volume
This enclosure follows the Proline X standing rule for dual sealed builds: two fully separate chambers split by a bonded full height 3/4 inch MDF divider, each driver in its own airspace with its own polyfill.
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 either would have on its own. A full divider removes that entirely. One shared side mounted terminal cup feeds both driver positions in parallel, so the cabinet stays a single connection point.
Net Volume, Not Gross
Each chamber is built at 0.80 cubic feet net per driver, 1.60 cubic feet net total, out of 1.78 gross. That per chamber figure is Morel's own sealed recommendation of 22.7 liters, so each driver sees the same alignment it would get on its own: Qtc 0.966 with a predicted F3 of 34.2 Hz, computed from Morel's published Fs 24 Hz, Qts 0.6 and Vas 49.4 liters. Morel publishes 36 Hz at this volume, agreement inside about 2 Hz.
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.
Qts is 0.6, so system Qtc cannot fall below 0.6 in any sealed enclosure regardless of volume. The alignment sits just under unity with a modest lift near the corner frequency, which is the driver's intended character.
Be Realistic About the Size
At 10.75 inches tall this is one of the two tallest cabinets in the Down Fire line. It is a cargo floor, rear wall, or behind the bench build, not an under seat one. The footprint stays the standard 30 by 15 inches, so it occupies no more floor area than any other Down Fire cabinet; it simply stands taller to give each driver its full 0.80 cubic feet. Measure your vertical clearance before ordering.
If clearance is the constraint, the single 12 inch PowerSlim cabinet at 6.375 inches and the dual 10 inch at 7.6875 inches are the alternatives.
Down Fire Construction
Cut with V-groove and dado joinery on our ShopSabre routers from Langboard Elite 3/4 inch MDF. 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. Both drivers fire down into the floor, and all external dimensions are measured in the down fire position.
Double Baffle, Flush Recess
Both front baffles are 1.5 inches, two bonded 3/4 inch sheets, with the outer layer machined as a flush recess so each driver bolts to the inner layer. That recovers 3/4 inch of internal clearance at both 10.6 inch openings.
Side-Mounted Terminal Cup
One Proline X ABS and carbon fiber composite cup with stainless hardware and copper ring terminals, pre-wired in 12 gauge OFC to both driver positions. Side mounted so it stays accessible with the baffles facing the floor.
Separate Chambers
A full height 3/4 inch bonded MDF divider gives each driver its own sealed 0.80 cubic feet and its own polyfill. Perimeter cross-bracing runs the cabinet, and each driver bolts through its own set of 8/32 threaded inserts.
Power and Warranty
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.
Each driver carries dual 4 ohm coils, so final impedance is set at the drivers, not at the cup. Wire both drivers identically, since mismatched wiring between chambers splits power unevenly. Confirm the resulting load against your amplifier's minimum stable impedance before powering the system.
The enclosure carries a 1 year limited warranty. Bring your own pair of Morel Ultimo PowerSlim PS124D; the drivers are purchased separately.
Cut for the Driver, Not the Catalog
Every Performance Optimized cabinet is cut to one driver's cutout, mounting depth and displacement, then built one at a time in Tullahoma, Tennessee.
| Series | Proline X Performance Optimized Down Fire |
| Compatible Driver | Morel Ultimo PowerSlim PS124D (DVC 4Ω) | Pair Required |
| Enclosure Type | Sealed | Dual Driver | Down Fire Geometry | Floor-Coupled |
| Chamber Configuration | Two Fully Separate Chambers | Full Divider | Single Shared Side-Mounted Terminal Cup |
| Firing Direction | Down Firing - Both Drivers Fire Toward Floor |
| External Width | 30 Inches |
| External Depth | 15 Inches |
| External Height | 10.75 Inches |
| Dimension Reference | All External Dimensions Measured In Down Fire Position |
| Total Internal Gross Volume | 1.78 Cubic Feet |
| Per-Chamber Net Volume | 0.80 Cubic Feet - Matches Morel Spec of 22.7 Liters |
| Total Net Volume | 1.60 Cubic Feet |
| Manufacturer Target Volume | 22.7 Liters Per Driver Published By Morel |
| Target Qtc Per Chamber | 0.966 (Computed from Published T/S) |
| Predicted F3 Per Driver | 34.2 Hz Computed | Morel Publishes 36 Hz |
| 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) |
| Mounting Depth Required | 3.4 Inches / 86mm (Morel Spec) |
| Woofer Opening (Each) | 10.6 Inches / 268.6mm Cutout (Morel Spec) |
| Standoffs | None - Cabinet Sits Flat In The Down Fire Position |
| Material | Langboard Elite 3/4" MDF |
| Construction | ShopSabre CNC / Perimeter Cross-Brace |
| Joinery | V-Groove and Dado (CNC-Cut) |
| Panel Thickness | 3/4 Inch |
| Front Baffle Construction | Double-Layer 1.5" MDF at Both Driver Positions |
| Chamber Divider | 3/4" MDF Full Bonded Panel |
| Corner Profile | Square (Down Fire Series Standard) |
| 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 |
| Terminal Cup | One Proline X ABS/Carbon Fiber Composite | Side Mounted | 12g OFC Pre-Wired to Both Driver Positions |
| Internal Wiring | 12 Gauge OFC to Both Driver Positions |
| Damping | Polyfill Pre-Installed Per Chamber |
| Recommended Power Per Driver | 350-700 Watts RMS (Morel Rated Range) |
| Carpet Finish | Dark Gray Trunkliner (Standard) or Plush Black |
| Weight | 47 lb |
| 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
0.80 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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