Proline X PO 12-S DF NSW sealed down fire enclosure, front panel on 1.75 inch feet, 30 by 10.3 inches.

Proline X PO 12-S DF NSW sealed down fire enclosure, end panel with recessed terminal cup, 15 by 10.3 inches.

Proline X

Performance Optimized Down Fire Sealed 12" Enclosure | NVX NSW12v3

Q: Does this fit the NVX NSW12v3, and will any other 12 inch fit?

The NSW12v3, yes, in either coil (NSW122v3 or NSW124v3). The baffle is cut to 10.86 in, NVX's published cutout, under the 12.46 in frame. The 6.00 inch motor clears the cabinet with 3.51 inch to spare. One cabinet serves both coils: the NSW122v3 (D2) reads Qtc 0.659 with half power at 50.4 Hz, and the NSW124v3 (D4) reads Qtc 0.755 at 46.8 Hz.Any other 12, no. The airspace is worked out from the NSW12v3's own Qts and Vas, and a different woofer that happened to drop into the hole would not see the alignment printed on this page.

Q: Why 1.63 cubic feet, and what alignment does it target?

1.63 cubic feet is split between the coils' Butterworth volumes (1.22 for the D2, 2.25 for the D4) on the D2 figures (Fs 34.7 Hz, Qts 0.49, Vas 37.7 liters): Qtc 0.659, half power at 50.4 Hz. One cabinet serves both coils: the NSW122v3 (D2) reads Qtc 0.659 with half power at 50.4 Hz, and the NSW124v3 (D4) reads Qtc 0.755 at 46.8 Hz.NVX's manual and product pages are the only published source for this driver, so treat the Qtc as good to a few hundredths.

Q: What amplifier power should I run, and how should I wire it?

NVX rates the NSW12v3 at 500 watts RMS, so target 350 to 500 watts RMS at the final load.The NSW122v3 (D2) wires to 4 ohms with its coils in series or 1 ohm in parallel. The NSW124v3 (D4) wires to 8 ohms in series or 2 ohms in parallel. Anything under 1 ohm, and many amplifiers at 1 ohm, is outside what the amplifier is built for; series wiring is the safe default. Confirm your amplifier's minimum stable impedance first.

Q: How tall is this once the standoffs are on?

The cabinet is 10.26 inches tall measured in the down fire position, and that figure excludes the standoffs. The standoffs hold 1.75 inches under the baffle, so plan your space around a finished stack of roughly 12.01 inches.The footprint is the standard Performance Optimized down fire platform, 30.00 inches wide by 15.00 deep. Height is the only dimension solved to the driver.

Q: Why is the front baffle double-layered?

The baffle is two bonded 3/4 inch sheets, 1.5 inches through. A single 3/4 inch panel flexes under the pressure a 12 inch woofer puts on it at 500 watts, which smears output and works the driver loose over time; the second layer stiffens the face and gives the mounting hardware twice the material to bite.The outer layer is machined as a flush recess to the 12.46 inch frame, so the driver bolts to the inner layer.

Q: What is the expected low-frequency extension?

Anechoic F3 is 50.4 Hz on the D2, with system resonance at 46.7 Hz. Below Qtc 0.707 the rolloff is gentle and F3 sits above fc, which is what a damped sealed box does.Those figures exclude cabin gain. In a car the cabin's transfer function adds real output below 50 Hz, so in-vehicle response runs deeper than the numbers above.

Q: Do I need to add polyfill or damping?

No. Polyfill is already installed as a light wall lining to control internal reflections, and the quantity is chosen so it does not change the acoustic volume.Do not add more. Packing a sealed box with fill makes it behave as though it were larger, which walks the alignment away from the 1.63 cubic feet this cabinet was built to.

Q: Is the driver included, and are the threaded inserts installed?

No driver. This is an enclosure only. You receive the cabinet finished in plush black carpet, one side-mounted pre-wired terminal cup, the polyfill lining already in place, the standoffs, and threaded inserts pressed on NVX's published 11.73 inch bolt circle with stainless machine screws.The NVX NSW12v3 is purchased separately, and the cabinet is cut direct fit to it, not a general purpose 12 inch box.

SKU: PO 12-S DF NSW

QUICK SPECS

Alignment: 1.63 cu ft net, Qtc 0.659 (D2), F3 50.4 Hz
Driver: NVX NSW12v3 (NSW122v3 D2 or NSW124v3 D4), 500 W RMS, 12.5 mm Xmax, 6.00 in mounting depth
Standoffs: Included, 1.75 in, shipped uninstalled. Installed height near 12.01 in
Cabinet: 30.00"W x 15.00"D x 10.26"H in down fire position, excludes standoffs, square corners

Shipping Included No freight charges at checkout. What you see is what you pay.

Built in Tennessee CNC cut from 3/4" Langboard Elite MDF. V-groove and dado joinery.

Advanced Terminal Cup Built in-house. ABS/Carbon Fiber. Stainless steel hardware. Copper ring terminals.

$ 279.99

In Stock and Ready to Ship

Financing available. Choose Shop Pay Installments at checkout.

Performance Optimized Down Fire Sealed 12" Enclosure | NVX NSW12v3

$ 279.99

More enclosures cut for NVX subwoofers: NVX Subwoofer Boxes

Enclosure Type Sealed

External Dimensions 30.00" W x 15.00" D x 10.26" H (measured in down fire position, excludes standoffs)

Gross Volume 1.72 cu ft

Net Volume 1.63 cu ft

Shipping Weight 44 lbs

Front Panel Thickness 1.5"

INSTALLER'S TAKE

Measure the installed height, not the cabinet height. The box is 10.26 tall on its own and the standoffs add 1.75, so plan around 12.01 inches of stack on the 30 by 15 footprint.

Airspace set the height here, 1.63 cubic feet; the motor clear the lid with 3.51 to spare.

Floor slot is 0.75 times the cone area at the 1.75 standoff, under the 1.0 I like. Taller feet fix it if the floor allows.

Cut is 10.86, NVX's own figure, and the inserts are already pressed on their 11.73 bolt circle. It is sealed, so leave the polyfill as it is and run it at 500 watts or under.

Product Details

Proline X Performance Optimized Down Fire 12" Sealed

Cut and tuned for the NVX NSW12v3

V-Groove and DadoLangboard Elite MDF1.63 cu ft NetStandoffs Included

1.63cu ft net

0.659system Qtc, D2

50.4 HzF3 rolloff, anechoic

10.26 incabinet height, excludes standoffs

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.	A shared 30 by 15 inch platform, with cabinet height as the variable. This build sits on that platform at 10.26 inches tall, the height that holds 1.63 cubic feet.	Compact per driver footprint.
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.	Threaded inserts pressed on the published bolt circle, stainless machine screws included.	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 driver's own numbers. A Performance box fits your subwoofer. A Performance Optimized box was built for it.

Built Around the NVX NSW12v3

Nothing about this cabinet is generic. The baffle is cut to 10.86 in, NVX's published cutout, under the 12.46 in frame. The airspace lands on 1.63 cubic feet net.

The NSW12v3 is NVX's 12 inch, rated 500 watts RMS, with 12.5 mm of excursion. It is 6.00 inches deep, which matters on a down fire, where the motor rises into the cabinet. Every figure comes from NVX's owner's manual and product pages for the NSW122v3 and NSW124v3, including the 0.080 cubic foot driver displacement and the bolt circle, so nothing here is estimated.

Net Volume, Not Gross

We build this cabinet at 1.63 cubic feet net, out of 1.72 gross after the brace and the 0.080 cubic foot driver displacement NVX publishes. At 1.63 cubic feet the NSW12v3 D2 lands at Qtc 0.659 with half power at 50.4 Hz. One cabinet serves both coils: the NSW122v3 (D2) reads Qtc 0.659 with half power at 50.4 Hz, and the NSW124v3 (D4) reads Qtc 0.755 at 46.8 Hz.

True net, not marketing net. Internal volume is calculated from the machined cavity dimensions and the driver's published displacement, not guessed from external dimensions minus wall thickness.

Driver	System Qtc	fc	F3
NSW122v3 dual 2 ohm	Qtc 0.659	46.7 Hz	50.4 Hz
NSW124v3 dual 4 ohm	Qtc 0.755	49.8 Hz	46.8 Hz

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 the cabinet airtight under sustained pressure cycling. Corners are square on Down Fire cabinets.

The cabinet measures 30.00 inches wide by 15.00 inches deep by 10.26 inches tall, measured in the down fire position and excluding standoffs. Plan the space around the installed height rather than the cabinet height: the standoffs hold 1.75 inches under the baffle, so the finished stack sits near 12.01 inches.

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. That recovers 3/4 inch of internal clearance.

Side-Mounted Terminal Cup

Proline X ABS and carbon fiber composite cup 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.

Standoffs Included

NVX publishes no front clearance figure for the NSW12v3, so this cabinet uses the Proline X standard 1.75 inch standoff, shipped with every enclosure and left uninstalled so you can place them to suit your floor. At that height the floor slot is 0.75 times the cone area, under the 1.0 we aim for. The 12.5 mm of excursion on this cone moves a lot of air, so if the floor allows, taller feet or a front-firing install give it more room.

Motor Clearance and Orientation

The motor rises off the baffle into the cavity, so on a down fire cabinet the clearance that matters runs to the top panel. The 6.00 inch mounting depth puts the motor 4.50 inches into a 8.01 inch cavity, leaving 3.51 inches above the motor against a 0.75 inch minimum. Height was set by the airspace, above the minimum the clearance alone would have required.

NVX does not publish a position on down firing this driver, and this cabinet makes no claim on their behalf. The feet ship uninstalled, so if you would rather run it front firing or up firing, that is a decision you can make at install time without changing anything about the enclosure.

Power, Mounting and Warranty

NVX rates the NSW12v3 at 500 watts RMS. The NSW122v3 (D2) wires to 4 ohms with its coils in series or 1 ohm in parallel. The NSW124v3 (D4) wires to 8 ohms in series or 2 ohms in parallel. Anything under 1 ohm, and many amplifiers at 1 ohm, is outside what the amplifier is built for; series wiring is the safe default. Confirm the load against your amplifier's minimum stable impedance before powering the system.

NVX publishes the 11.73 in bolt circle for the NSW12v3, so the threaded inserts are pressed at the shop and the stainless machine screws are in the box: set the driver in the recess and bolt it down. The enclosure carries a 1 year limited warranty. Bring your own NSW12v3; the driver is purchased separately.

Cut for the Driver, Not the Catalog

Built one at a time in Tullahoma, Tennessee, with standoffs and a 1 year limited warranty. Questions on fitment or amplifier matching, call 931-563-5151.

Specifications

Specification	Value
Series	Proline X Performance Optimized Down Fire
Compatible Driver	NVX NSW12v3 (NSW122v3 D2 or NSW124v3 D4), quantity 1. Direct fit
Configuration	Single 12 inch, sealed down fire
Mounting Position	Trunk or cargo floor, baffle facing down on standoffs
Firing Direction	Downward. Feet ship uninstalled, so front or up firing is also possible
External Width	30.00 in
External Depth	15.00 in
External Height	10.26 in in the down fire position, excludes standoffs
Installed Height	12.01 in including the 1.75 in standoff
Internal Volume, Gross	1.72 cu ft
Internal Volume, Net Acoustic	1.63 cu ft after the brace and the 0.080 cu ft displacement NVX publishes
Height Set By	Airspace; clearance alone would allow a lower cabinet
Driver Mounting Depth	6.00 in required, 3.51 in clearance above the motor
Floor Slot	0.75 times the cone area at the 1.75 in standoff
Alignment, D2	Qtc 0.659, fc 46.7 Hz, F3 50.4 Hz anechoic
Alignment, D4	Qtc 0.755, fc 49.8 Hz, F3 46.8 Hz anechoic
Woofer Opening	10.86 in, NVX's published cutout
Frame Outer Diameter	12.46 in, NVX published
Bolt Circle	11.73 in, NVX published; threaded inserts pre-installed
Driver Displacement	0.080 cu ft, NVX published
NSW122v3 (D2) Fs / Qts / Qes / Qms / Vas	34.67 Hz / 0.489 / 0.534 / 5.79 / 37.70 L
NSW124v3 (D4) Fs / Qts / Qes / Qms / Vas	36.92 Hz / 0.560 / 0.620 / 5.75 / 37.83 L
Driver Sd	511 cm2, published by NVX
Xmax	12.5 mm, NVX spec; the manual does not state one-way or peak to peak
Driver Power Handling	500 W RMS, NVX spec
Wiring Options	The NSW122v3 (D2) wires to 4 ohms with its coils in series or 1 ohm in parallel. The NSW124v3 (D4) wires to 8 ohms in series or 2 ohms in parallel. Anything under 1 ohm, and many amplifiers at 1 ohm, is outside what the amplifier is built for; series wiring is the safe default.
Parameter Source	NVX NSW122v3 / NSW124v3 owner's manual and nvx.com product pages
Material	Langboard Elite MDF
Construction	CNC cut, V-groove and dado joinery, square corners
Panel Thickness	0.75 in
Front Baffle	1.5 in double baffle, outer layer machined as a flush recess
Internal Bracing	Windowed brace, dadoed to the shell
Driver Mounting	Threaded inserts pre-installed on the published bolt circle, stainless machine screws included
Terminal Cups	One Proline X ABS and carbon fiber composite, side mounted, pre wired 12 gauge OFC
Standoffs	Included, 1.75 in, shipped uninstalled
Damping	Light polyfill wall lining, does not alter acoustic volume
Carpet	Plush black
Shipping Weight	44 lb
Warranty	1 Year Limited
Built In	Tullahoma, Tennessee

Performance Graphs

Net airspace

1.63

cu ft

System Qtc

0.66–0.76

sealed

Half power

46.8–50.4

Hz · F3

Xmax at

323

W RMS · no filter

With 25 Hz subsonic

438

W RMS · +36%

Amplifier

500

W RMS recommended

This enclosure holds 1.63 cu ft net . In it the NVX NSW12v3 runs a system Qtc of 0.66–0.76 with half power at 46.8–50.4 Hz, and the cone reaches its 12.5 mm travel limit at 323 W, below the driver’s 500 W thermal rating, so travel is what stops you here, not heat. Run a subsonic filter at 25 Hz and that becomes 438 W — +115 W, or 36 percent more power for the same 12.5 mm of travel.

01Is it a sealed driver?

Efficiency bandwidth product places the motor before anything else is decided.

EBP = Fs ÷ Qes = 59.5–64.9

dual 2 ohm · EBP 64.9dual 4 ohm · EBP 59.5

At 59.5–64.9 the NSW12v3 sits in the transition band, not the sealed band. That is not a mismatch: a transition motor works in either alignment, and sealed buys a smaller box and a gentler roll-off at the cost of some low-end output. Stage 02 shows what this airspace actually does with it.

02What the box does to it

1.63 cu ft against a 37.7 L Vas.

α = Vas ÷ Vb = 0.82 · Fc = Fs√(α+1) = 47–50 Hz · Qtc = 0.66–0.76

dual 2 ohm · Qtc 0.66, Fc 47 Hz, F3 50.4 Hzdual 4 ohm · Qtc 0.76, Fc 50 Hz, F3 46.8 Hz

The box lifts resonance from 34.7–36.9 Hz free-air to 47–50 Hz and half power lands at 46.8–50.4 Hz, anechoic, before any cabin gain. Figures are NVX’s published NSW12v3 parameters from its owner’s manual and product pages, displacement included (0.080 cubic feet). One cabinet serves both coils; both are plotted.

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 12.5 mm — and a bigger one once a subsonic filter stops it wasting travel below the passband.

P_Xmax = 323–361 W unfiltered → 438–459 W with a 25 Hz subsonic

dual 2 ohm · 323 W, no filterdual 4 ohm · 361 W, no filterdual 2 ohm · 459 W with subsonic at 25 Hz, 24 dB/octdual 4 ohm · 438 W with subsonic at 25 Hz, 24 dB/octXmax 12.5 mm one-way

Every trace touches the limit and no further, because each is drawn at the exact power that puts that coil on 12.5 mm. Unfiltered that is 323 W, reached first at 20 Hz. It sits under the 500 W the driver can take thermally, so the enclosure sets the ceiling, not the voice coil. The dashed traces are the same driver behind a subsonic filter at 25 Hz, 24 dB/oct: stopping the cone wasting travel below the passband lets it take 438 W before hitting the same 12.5 mm. That is 36 percent more amplifier for the price of one filter setting.

Param	Value	Unit	Note
Fs	34.67 / 36.92	Hz	free-air resonance
Qts	0.489 / 0.560		dual 2 ohm / dual 4 ohm
Vas	37.70 / 37.83	L	equivalent compliance
Sd	510.6	cm²	effective piston area
Xmax	12.5	mm	one-way linear travel
Pe	500	W	continuous RMS
SPL	86.5	dB	1 W / 1 m, derived from T/S

Driver parameters as published by NVX NSW12v3 owner’s manual. Curves computed against this enclosure’s actual net airspace.

Materials

Material

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.

Specifications

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

Internal Bond

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.

Stiffness

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.

Screw Holding

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.

Sourcing

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.