Proline X
Performance Optimized Down Fire Sealed 12" Enclosure | Prodigy NB3-12
SKU: PO 12-S DF NB3
- Alignment: 1.02 cu ft net, Qtc 0.690, Fc 51.5 Hz, F3 52.8 Hz: maximally flat sealed tune
- Driver: Prodigy NB3-12D4, 800W RMS, 11mm Xmax at 70% BL, 3.375" mounting depth, 3.0" voice coil
- 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 7.625"H measured in down fire position, square corners
Financing available. Choose Shop Pay Installments at checkout.
Performance Optimized Down Fire Sealed 12" Enclosure | Prodigy NB3-12
Proline X Performance Optimized Down Fire 12" Sealed
Cut and tuned for the Prodigy NB3-12D4
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 Prodigy NB3-12D4's own published numbers. A Performance box fits your subwoofer. A Performance Optimized box was built for it.
Built Around the Prodigy NB3-12
Nothing about this cabinet is generic. The baffle is bored to the NB3-12's 10.625 inch cutout, and the internal height is set by the driver's 3.375 inch mounting depth. The finished cabinet stands 7.625 inches tall, which puts a full 12 inch driver into spaces normally reserved for a 10.
The NB3-12D4 is an 800 watt RMS dual 4 ohm driver with 11mm of one way Xmax at 70 percent BL. Prodigy kept the heavy hardware on this one rather than shrinking it to save depth: an 80 ounce ferrite magnet and a 3.0 inch four layer copper voice coil, where most shallow 12s drop to a 2 or 2.5 inch coil. An FEA designed center pole vent pulls heat out of the gap. Cone is treated paper on a rubber surround in a stamped steel frame, with a Nomex and cotton blend spider and flat stitched tinsel leads.
A BL of 23.96 on a shallow driver is the number worth noticing. It follows directly from the coil Prodigy refused to shrink.
Net Volume, Not Gross
Gross internal volume is 1.155 cubic feet. After the driver's published 0.13 cubic feet of displacement, the as built figure is 1.02 cubic feet net. At that volume the system lands at Qtc 0.690, Fc 51.5 Hz, and a predicted anechoic F3 of 52.8 Hz, which sits right on the maximally flat shoulder.
That is where you want a driver carrying a 29.665 liter Vas against a 36.2 Hz Fs and a Qts of 0.485. Building larger would push the alignment overdamped and buy very little extension. Building smaller would raise Qtc into punchy territory and lift the corner frequency with it. 1.02 net is the balanced point, and it still fits inside a 7.625 inch down fire profile.
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.
Anechoic F3 understates in vehicle performance. A cabin produces rising gain below roughly 60 Hz, and a sealed enclosure rolls off at 12 dB per octave, so the two work against each other favorably. Firing down into a floor, in car response typically extends well below the anechoic number. We publish the anechoic figure because it is the honest measurable spec.
Twelve Inches on a Ten Inch Footprint
This cabinet shares the 30 by 15 inch footprint of the 10 inch Down Fire enclosure in the same series and stands 1.375 inches taller. That 1.375 inches buys a 15.3 Hz lower anechoic F3 and a better alignment: 52.8 Hz at Qtc 0.690 here, against 68.1 Hz at Qtc 0.526 on the 10.
The difference is the drivers, not the cabinet design. The NB3-12 has a 29.665 liter Vas against the NB3-10's 14.43 liters, which gives it far more room to reach a flat alignment. Unlike the shallow 10, the NB3-12 does not force a choice between good damping and a low corner frequency. If your install has the vertical clearance, this is the one to build.
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.
External dimensions are 30 inches wide by 15 inches deep by 7.625 inches tall, measured in the down fire position. Finished weight is 33 pounds. The driver fires down into the floor, so the cabinet couples into the boundary directly beneath it.
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. A 10.625 inch opening in a cabinet this short means the baffle is doing real structural work, not just providing thread engagement.
Side-Mounted Terminal Cup
Proline X ABS and carbon fiber composite cup, recessed, 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.
Perimeter Cross-Bracing
A perimeter cross-brace stiffens the panel spans around the large baffle cutout, and polyfill damping is pre-installed. The driver lands on 8/32 threaded inserts with stainless machine screws included.
Power and Warranty
Target 600 to 800 watts RMS at the woofer impedance. Prodigy rates the NB3-12D4 at 800 watts RMS continuous. It is a dual 4 ohm driver, so a single unit wires to 2 ohms or 8 ohms.
The enclosure carries a 1 year limited warranty. Bring your own Prodigy NB3-12D4; the driver is purchased separately.
Cut for the Driver, Not the Catalog
The volume, the cutout and the cabinet height all come from the NB3-12's own published numbers. Built one at a time in Tullahoma, Tennessee.
| Series | Proline X Performance Optimized Down Fire |
| Enclosure Type | Sealed | Down Fire Geometry | Floor-Coupled |
| Driver-Specific Fitment | Prodigy NB3-12D4 (DVC 4Ω) |
| Internal Volume (Gross) | 1.155 Cubic Feet |
| Internal Volume (Net After Displacement) | 1.02 Cubic Feet |
| Target System Qtc | 0.690 (Maximally Flat | Based on Published T/S) |
| Predicted Fc | 51.5 Hz |
| Predicted F3 (Anechoic) | 52.8 Hz |
| Driver Displacement | 0.13 Cubic Feet (Published by Prodigy) |
| Baffle Configuration | Down Firing - Driver Fires Toward Floor |
| Material | Langboard Elite 3/4" MDF |
| Front Baffle Construction | Double-Layer 1.5" MDF (Two 3/4" Sheets Bonded) |
| Joinery | V-Groove and Dado (CNC-Cut) |
| Corner Profile | Square (Down Fire Series Standard) |
| Construction | ShopSabre CNC / Perimeter Cross-Brace |
| External Width | 30 Inches |
| External Depth | 15 Inches |
| External Height | 7.625 Inches |
| Dimension Reference | All External Dimensions Measured In Down Fire Position |
| Mounting Hole Diameter | 10.625 Inches (Prodigy Spec) |
| Mounting Depth Required | 3.375 Inches (Prodigy Spec) |
| 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 | 600-800 Watts RMS (Prodigy Rated: 800W RMS Continuous) |
| Carpet Finish | Plush Black |
| Bundle Options | Enclosure Only (Bring Your Own NB3-12D4) |
| 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
1.02 cu ft against a 29.7 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 | 36.20 | Hz | free-air resonance |
| Qts | 0.485 | D4 | |
| Vas | 29.66 | L | equivalent compliance |
| Sd | 535.5 | cm² | effective piston area |
| Xmax | 11 | mm | one-way linear travel |
| Pe | 800 | W | continuous RMS |
| SPL | 85.4 | dB | 1 W / 1 m, derived from T/S |
Driver parameters as published by prodigyaudio.com product page; Sd derived from Vas and Cms; published Fs runs below what their own Cms and Mms imply. 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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