Proline X

Performance Optimized Wedge Sealed 12" Enclosure | Sundown Audio SA-12

Q: Will this enclosure fit every version of the SA-12?

Yes. The SA-Classic 12, the SA-Series v.2 12 and the SA-Series v.3 12 share a basket within two tenths of an inch, in D2 and D4. The cutout is cut to the v.3 at 11.20 in and the depth clears the v.3's 8.4 in, so every generation and coil drops in. Each has its own Qtc in this box; the page lists all six.

Q: How does a wedge enclosure improve the sound in a trunk installation?

The angled seat-side face matches the roughly 20 degree lean of a factory rear seat, so the cabinet sits flat against it instead of leaving a wasted triangle. The vertical trunk-lid-side face carries the driver, firing rearward into the trunk cavity.

Q: Why a rear-firing wedge instead of a plain box?

A rectangular box of this volume wastes the triangle of space a leaning rear seat creates, and firing into the trunk lid rather than at the seat back gives the cabin a smoother path to the passengers. The wedge takes the same air volume and puts it where the car actually has room.

Q: What is the expected low-frequency extension?

Half power lands between 46 to 62 Hz anechoic depending on the generation, before any cabin gain. Qtc runs 0.55 to 0.69 by generation and coil. These figures exclude cabin gain, which in most vehicles adds real output below 40 Hz. Sundown publish free-air resonance between 33.6 to 38.9 Hz across the six.

Q: Do I need to add polyfill or damping?

No. Polyfill is already installed as a light wall lining and the quantity is chosen so it does not change the acoustic volume. Do not add more.

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 and the polyfill lining installed. Sundown Audio publishes no mounting hole locations for the SA-12, so the threaded inserts are not pressed before it ships. The threaded insert kit comes in the box instead: 8 to 12 inserts sized to the woofer, the correct drill bit, 2.5 inch allen-head screws, an allen key and woofer gasket tape. You set the inserts where the woofer's own holes fall when you mount it.

SKU: PO 12-S W SA12 BB

QUICK SPECS

Best For: Sundown Audio SA-12 Trunk-Fit Builds, any generation
Net Volume: 1.00 cu ft (1.19 cu ft Gross), Sundown's recommended sealed volume
Alignment: Qtc 0.55 to 0.69, fc 45 to 54 Hz, F3 46 to 62 Hz by generation and coil
Driver Match: SA-Classic 12, SA-12 v.2 or SA-12 v.3 (D2 or D4)
Construction: Rear-Firing Wedge | V-Groove/Dado | Double 1.5" Baffle | Threaded Insert Kit included

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.

$ 299.99

Acrylic Insert Color

In Stock and Ready to Ship

Financing available. Choose Shop Pay Installments at checkout.

Performance Optimized Wedge Sealed 12" Enclosure | Sundown Audio SA-12

Enclosure Type Sealed

External Dimensions 18.45" W x 15" H x 15.30" D at base tapering to 9.84" D at top

Gross Volume 1.19 cu ft

Net Volume 1.00 cu ft

Weight 27.8 lbs

Front Panel Thickness 1.5"

INSTALLER'S TAKE

I built this box to the sealed volume Sundown themselves publish for the SA-12, 1.00 cubic feet net, and because the Classic, the v.2 and the v.3 share a basket within two tenths of an inch, one cabinet and one listing covers all three in either coil.

The Classic sits near the Butterworth point in this volume; the v.2 and v.3 come out drier, with F3 near 60 Hz anechoic, which is how Sundown voiced them and where cabin gain does its work. If you want a ported box for the v.2 or v.3 at its full rating, that is the Professional SA-12, not this one.

Sundown publishes no mounting hole locations, so the inserts are not in the baffle when the box arrives. The insert kit is in the box: set the inserts where the woofer's own holes fall, with the drill bit and the 2.5 inch allen-head screws in the kit, and lay the gasket tape before the woofer goes down.

Measure the base depth. This cabinet is 15.30 inches deep at the trunk floor, 9.84 at the top, and 18.45 wide. It is deeper at the base than it is tall, because the v.3 carries an 8.4 in motor and the cabinet has to clear it.

Product Details

Performance Optimized Wedge | Sundown Audio SA-12

12" Sealed Wedge Enclosure | Rear-Firing Trunk-Load Design

1.00 ft3 Net1.19 ft3 GrossQtc 0.55 to 0.69Single Chamber Wedge18.45" x 15" x 9.84/15.30"Built in Tennessee

The Sundown Audio SA-12 in a Sealed Wedge

Sundown Audio's SA-12 has shipped in three generations, the SA-Classic 12, the SA-Series v.2 12 and the SA-Series v.3 12, each in D2 and D4 coils, and all six fit this one cabinet. The alignment below is computed from Sundown's published Thiele-Small parameters, carried per generation and per coil because Sundown publish them that way.

1.00 cubic feet net, which is the sealed volume Sundown Audio themselves recommend for the SA-12, and the one cabinet covers every generation of the driver. In that volume the SA-Classic 12 lands at Qtc 0.69 (D2) and 0.67 (D4) with F3 at 46 and 49 Hz; the SA-Series v.2 12 lands at Qtc 0.63 (D2) and 0.63 (D4) with F3 at 61 and 54 Hz; and the SA-Series v.3 12 lands at Qtc 0.57 (D2) and 0.55 (D4) with F3 at 60 and 62 Hz. The Classic sits close to the Butterworth point; the v.2 and v.3 run drier and lean on cabin gain for the bottom octave, which is how Sundown voiced them.

Threaded insert kit ships with this box. Sundown Audio publishes no mounting hole locations for the SA-12, so the threaded inserts are not pressed before it ships. The threaded insert kit comes in the box instead: 8 to 12 inserts sized to the woofer, the correct drill bit, 2.5 inch allen-head screws, an allen key and woofer gasket tape. You set the inserts where the woofer's own holes fall when you mount it.

Trunk-Load Wedge Design Explained

The driver mounts on the vertical trunk-lid-side face and fires rearward into the trunk cavity.

Seat-Side Face Matches Seat Lean

Angled face matches the roughly 20 degree factory seat lean.

Trunk-Lid-Side Face Fires the Woofer

Vertical baffle, cone firing rearward into the trunk cavity.

Trunk Cavity Loading

The trunk acts as an acoustic extension for a smoother presentation.

Preserves Trunk Cargo Space

The wedge tucks against the seat back and the space in front stays usable.

Engineered for the Sundown Audio SA-12

The three generations share a basket within two tenths of an inch: the cutout is cut to the v.3 at 11.20 in, the mounting depth allowance clears the v.3's 8.4 in, and the cosmetic recess is cut to the 12.84 in frame Sundown publish.

Alignment Numbers

Qtc 0.55 to 0.69 · fc 45 to 54 Hz · F3 46 to 62 Hz anechoic, across the six generation and coil combinations

Mounting Geometry

Vertical baffle CNC cut to 11.20 in. Mounting depth available is 8.90 in against the 8.4 in the v.3 requires; the Classic and v.2 sit shallower. Driver displacement is Sundown's own figure for each generation, and the largest, 0.18 cu ft for the v.3, is the one deducted. Sundown Audio publishes no mounting hole locations for the SA-12, so the threaded inserts are not pressed before it ships. The threaded insert kit comes in the box instead: 8 to 12 inserts sized to the woofer, the correct drill bit, 2.5 inch allen-head screws, an allen key and woofer gasket tape. You set the inserts where the woofer's own holes fall when you mount it.

Performance Series Construction, Driver-Specific Tuning

Langboard Elite MDF

Premium 3/4 in MDF throughout.

V-Groove and Dado Joinery

CNC cut V-grooves at every panel intersection, sides and brace seated in dados.

Double-Layer 1.5" Front Baffle

Two bonded 3/4 in MDF sheets at the driver face.

Threaded Insert Kit Included

Sundown publish no hole locations, so the inserts, drill bit, allen-head screws, allen key and gasket tape ship in the box for you to set at the woofer's own holes.

Wiring the Sundown Audio SA-12 to Your Amplifier

A D2 coil carries two 2 ohm coils: 4 ohms in series or 1 ohm in parallel. A D4 coil carries two 4 ohm coils: 8 ohms in series or 2 ohms in parallel. Run the coils in series unless the amplifier is rated stable at the parallel load; 1 ohm is beyond most amplifiers.

Sundown rate the SA-Classic 12 at 1000 watts RMS, the v.2 at 1250 and the v.3 at 1500. Aim for roughly 70 to 100 percent of your generation's rating at the impedance you wire.

Built in Tennessee, Backed by Audio Intensity

Cut and assembled in Tullahoma, Tennessee on our own CNC equipment. Finished in plush black carpet, pre-wired terminal cup, 12 gauge OFC to the driver position. 1 year limited warranty. Enclosure only, the driver is purchased separately. Call or text 931-563-5151.

Sundown Audio SA-12: Built to Sundown's Own Sealed Volume

1.00 cubic feet net at Qtc 0.55 to 0.69, F3 46 to 62 Hz, one cabinet for every generation, cut direct fit and built to order in Tennessee.

Specifications

Specification	Value
Series	Proline X Performance Optimized Wedge
Compatible Driver	Sundown Audio SA-12: SA-Classic 12, SA-Series v.2 12, SA-Series v.3 12, D2 or D4, quantity 1. Direct fit
Configuration	Single 12 inch, single chamber sealed wedge
Mounting Position	Trunk or cargo area, tall face against the rear seat back
Firing Direction	Rearward into the trunk. Not a down fire design, no feet included
External Width	18.45 in
External Height	15 in at the seat face
External Depth	15.30 in at the base, tapering to 9.84 in at the top
Internal Volume, Gross	1.19 cu ft
Internal Volume, Net Acoustic	1.00 cu ft, Sundown's recommended sealed volume
Alignment	Qtc 0.55 to 0.69, fc 45 to 54 Hz, F3 46 to 62 Hz anechoic (six generation and coil combinations)
Driver Cutout	11.20 in, cut to the v.3
Driver Mounting Depth	8.90 in available, 8.4 in required by the v.3
Frame Outer Diameter	12.84 in, as published by Sundown
Driver Displacement	0.18 cu ft, Sundown's figure for the v.3
Power Handling	1000 W RMS Classic, 1250 W v.2, 1500 W v.3
Impedance	D2: 4 ohms in series or 1 ohm in parallel; D4: 8 ohms in series or 2 ohms in parallel
Xmax	19 to 22 mm one way by generation
Sensitivity	83.2 to 86.6 dB as published by Sundown, by generation
Material	Langboard Elite MDF
Construction	CNC cut, V-groove and dado joinery
Panel Thickness	0.75 in
Front Baffle	1.5 in, double baffle
Internal Bracing	Internal brace
Driver Mounting	Threaded insert kit included, not pre-installed: Sundown publish no mounting hole locations
Terminal Cups	One Proline X ABS and carbon fiber composite, side mounted, pre wired 12 gauge OFC
Damping	Light polyfill wall lining, does not alter acoustic volume
Carpet	Plush black
Weight	27.8 lb
Warranty	1 Year Limited
Built In	Tullahoma, Tennessee

Performance Graphs

Net airspace

1.00

cu ft

System Qtc

0.57–0.69

sealed

Half power

45.9–60.3

Hz · F3

Xmax at

914

W RMS · no filter

With 25 Hz subsonic

1295

W RMS · +42%

Amplifier

1500

W RMS recommended

This enclosure holds 1.00 cu ft net . In it the Sundown Audio runs a system Qtc of 0.57–0.69 with half power at 45.9–60.3 Hz, and the cone reaches its 19.0 mm travel limit at 914 W, below the driver’s 1500 W thermal rating, so travel is what stops you here, not heat. Run a subsonic filter at 25 Hz and that becomes 1295 W — +382 W, or 42 percent more power for the same 19.0 mm of travel.

01Is it a sealed driver?

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

EBP = Fs ÷ Qes = 58.1–66.7

Classic D2 · EBP 58.1v.3 D2 · EBP 66.7

At 58.1–66.7 the SA-12 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

1.00 cu ft against a 21.2 L Vas.

α = Vas ÷ Vb = 0.75 · Fc = Fs√(α+1) = 45–47 Hz · Qtc = 0.57–0.69

Classic D2 · Qtc 0.69, Fc 45 Hz, F3 45.9 Hzv.3 D2 · Qtc 0.57, Fc 47 Hz, F3 60.3 Hz

The box lifts resonance from 33.7–35.0 Hz free-air to 45–47 Hz and half power lands at 45.9–60.3 Hz, anechoic, before any cabin gain. One cabinet, six drivers: Sundown's three SA-12 generations in D2 and D4 all fit this box at Sundown's own recommended 1.00 cubic feet. The two ends of the range are plotted, the Classic D2 nearest the Butterworth point and the v.3 D2 the box is cut for; the rest fall between them. In this volume: Classic D2 Qtc 0.69, F3 46 Hz; Classic D4 Qtc 0.67, F3 49 Hz; v.2 D2 Qtc 0.63, F3 61 Hz; v.2 D4 Qtc 0.63, F3 54 Hz; v.3 D2 Qtc 0.57, F3 60 Hz; v.3 D4 Qtc 0.55, F3 62 Hz. The v.2 and v.3 run drier and lean on cabin gain.

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

P_Xmax = 914–1365 W unfiltered → 1295–2172 W with a 25 Hz subsonic

Classic D2 · 914 W, no filterv.3 D2 · 1365 W, no filterClassic D2 · 1295 W with subsonic at 25 Hz, 24 dB/octv.3 D2 · 2172 W with subsonic at 25 Hz, 24 dB/octXmax 19.0 mm one-way

Every trace touches the limit and no further, because each is drawn at the exact power that puts that coil on 19.0 mm. Unfiltered that is 914 W, reached first at 20 Hz. It sits under the 1500 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 1295 W before hitting the same 19.0 mm. That is 42 percent more amplifier for the price of one filter setting.

Param	Value	Unit	Note
Fs	33.71 / 35.00	Hz	free-air resonance
Qts	0.520 / 0.428		Classic D2 / v.3 D2
Vas	21.21 / 22.19	L	equivalent compliance
Sd	433.6 / 510.3	cm²	effective piston area
Xmax	19	mm	one-way, 19 mm on the Classic and v.2, 22 mm on the v.3; the smaller figure is plotted. Power is the v.3's 1500 W rating; the Classic is rated 1000 W and the v.2 1250 W
Pe	1500	W	continuous RMS
SPL	83.3	dB	1 W / 1 m, derived from T/S

Driver parameters as published by sundownaudio.com product pages, per generation. 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.