Proline X M10-S Micro Series enclosure, carpet wrapped, with the Arc Audio badge inset on the front panel.

A black car audio subwoofer box with a textured fabric cover, featuring a large silver and black Arc Audio subwoofer driver and a small silver port plug on the front, shown against a plain white background.

A black Arc Audio subwoofer enclosure with a textured fabric cover, featuring a large circular subwoofer driver and a BNC input connector on a white background.

Proline X

Proline X M12-S ARC A | Single 12" Sealed Subwoofer Enclosure | Loaded with Arc Audio A12

Q: What comes in this system?

A Proline X Micro Series sealed enclosure at 1.0 cubic foot net in plush black, with the Arc Audio A12 already mounted to 8/32 threaded inserts, wired and sealed against the baffle in your chosen D2 or D4 configuration. Polyfill is installed and wiring runs 12 gauge OFC to a recessed Proline X terminal cup. An amplifier, power wire and RCA cables are not included.

Q: Should I choose D2 or D4?

Whichever matches the load your amplifier is stable at. D2 wired parallel gives a 1 ohm final load or 4 ohms in series. D4 wired parallel gives 2 ohms or 8 ohms in series. Most single subwoofer builds run the D4 parallel at 2 ohms. Decide before ordering, because the driver is installed and the cabinet is sealed before it ships.

Q: Do I need an amplifier, and how much power?

Yes. This is a passive enclosure with no amplification built in. Target 250 to 300 watts RMS at your wired impedance from a Class D monoblock. The A12 is rated at 300 watts RMS, so a clean amplifier at that output is the correct match. A clean amplifier at the rated power will outperform a clipping one at double it. If you are keeping the factory head unit you will also need a line output converter or a DSP with speaker level inputs.

Q: Why 1.0 cubic foot?

Because that is what Arc Audio publishes as the optimum for the A12. Their sealed range is 0.85 to 1.25 cubic feet and 1.0 is the centre of it, which produces the flattest sealed response and the most controlled transient behaviour. Net volume here is calculated by summing each CNC cut layer's opening rather than estimated from external dimensions, so the figure is exact rather than approximate.

Q: Will this fit behind my seat?

Measure the width first. At 28.5 inches wide this is broader than people expect from a shallow 12, and width is usually what decides the install rather than the 7.5 inch depth. Behind a rear seat in a crew cab it generally goes. Under a seat it does not. Allow clearance for the terminal cup and amplifier leads on top of the cabinet dimensions.

Q: How does the A12 compare to the A10?

Same design intent, more output. The A12 is rated at 300 watts RMS against the A10's 250, and the larger cone moves more air at the same excursion. Character is the same: controlled, accurate, front stage friendly rather than built for a meter reading. The A10 cabinet is 24 inches wide and 6 deep, this one is 28.5 wide and 7.5 deep, so the A12 asks for more space in both directions.

Q: What is the warranty on this system?

The enclosure carries a 2 year limited warranty on craftsmanship and materials, which is the standard across the Micro Series and Professional Series. Performance and Performance Optimized enclosures carry 1 year. The Arc Audio A12 carries its own manufacturer warranty separately, handled through Arc Audio.

Q: Why does the driver mount to threaded inserts?

Because screws into MDF hold well the first time and progressively worse after that. The baffle carries 8/32 threaded inserts on the back face with stainless machine screws supplied, so the driver mounts to steel rather than into board. That gives consistent clamping force at every point and lets the driver come out and go back in cleanly at any service interval without stripping the hole.

SKU: M12-S ARC A D4

QUICK SPECS

Best For: Shallow 12 inch installs where depth is fixed by the vehicle
Configuration: Single 12" Sealed, Micro Series, loaded
Volume: 1.0 ft³ Net, Arc Audio's published optimum
Tuning: N/A, Sealed
Sonic Character: Controlled, accurate, front stage friendly

Proline X Enclosure: Built in Tennessee CNC-cut Langboard Elite 3/4" MDF, V-groove + dado joinery, recessed ABS/Carbon Fiber terminal cup.

Driver + Enclosure: Matched and Pre-Wired Subwoofer pre-installed and wired to the correct impedance. Connect your amplifier and it's ready to run.

Shipping Included No freight charges at checkout on orders to the lower 48. Alaska, Hawaii, and international orders are quoted live rates at checkout.

$ 629.99

Impedance

In Stock and Ready to Ship

Financing available. Choose Shop Pay Installments at checkout.

What's Included

Proline X Micro Series sealed enclosure, single 12 inch, 1.0 cu ft net, plush black
Arc Audio A12 subwoofer pre-installed in your chosen D2 or D4 configuration
Pre-wired 12 gauge OFC speaker wire to the terminal cup
Recessed Proline X ABS and carbon fiber terminal cup with stainless hardware and copper ring terminals
8/32 threaded inserts with stainless machine screws
Polyfill pre-installed and matched to this volume

Amplifier, power wire and RCA cables are not included.

Proline X M12-S ARC A | Single 12" Sealed Subwoofer Enclosure | Loaded with Arc Audio A12

Enclosure Type Sealed

External Dimensions 28.5"W x 14.75"H x 7.5"D

Net Volume 1.0 cu ft

Tuning Frequency N/A - Sealed

Cutout Diameter Direct Fit

Front Panel Thickness 1.5" Double-Layer Stack Fab

Max Mounting Depth Direct Fit

INSTALLER'S TAKE

Measure the width before anything else. At 28.5 inches this cabinet is wider than most people picture when they hear shallow 12, and width is what usually kills the install rather than depth. Behind a rear seat in a crew cab it generally goes. Under a seat it does not. Check the actual flat run you have and allow clearance for the terminal cup and your amplifier leads on top of the cabinet dimension.

The 5.25 inch mounting depth is the number that makes this work. It is not a shallow driver in the way the A10 is, it is a moderate depth 12 in a cabinet built tightly around it. If your space is genuinely tight in depth rather than width, measure to the millimetre before ordering, because there is not much margin either side.

The driver mounts to 8/32 threaded inserts rather than screws into board, so it will come out and go back in cleanly if you ever pull it for service. Your only work here is the amplifier run and securing the cabinet properly. A loaded 12 at this size carries real mass and needs anchoring to the vehicle rather than sitting loose on a carpeted floor.

Product Details

Proline X Micro Series Enclosure for the Arc Audio A12

Cut and tuned for the Arc Audio A12

CNC Stack-Fab Langboard Elite MDF 1.00 cu ft Net Fits Arc Audio A12

1.00cu ft net

1.176system Qtc

36 HzF3 rolloff

3.85 inA12 mounting depth

Built Around the Arc Audio A12

Nothing about this box is generic. Every layer is cut to the A12's published sealed target, with the baffle bored to the A12's 10.91 in cutout with 8/32 threaded inserts set on the back face, and clearance cut for its 3.85 in mounting depth.

The A12 carries a published Fs of 25.01 Hz, Qts of 0.612 and Vas of 76.32 litres, and an EBP of 38, which puts it in sealed enclosure territory. We ran the alignment math on that data and built the box to land where it belongs.

Net Volume, Not Gross

We build this cabinet at 1.00 cubic feet net, against a published recommendation of 1.0 cu ft gross. The volume quoted is true net internal airspace, measured after the walls, bracing and driver displacement are accounted for.

True net, not marketing net. Internal volume is calculated by summing each CNC cut layer's opening, not estimated from external dimensions minus wall thickness.

Proline X Micro Series Construction

This enclosure is stack fabricated 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 layer is a precision cut ring and the stacked layers do the joining themselves, so there is no butt joint or dado to flex or leak. Dowel reinforcement runs between layers as tension hardware only.

Threaded Inserts, Not Wood Screws

8/32 threaded inserts are set on the backside of the baffle so the driver mounts on machine screws. Pull it a dozen times and the threads are still there.

Pre-Wired Terminal Cup

Proline X ABS and carbon fiber composite cup with stainless hardware and copper ring terminals, pre-wired internally with 12 gauge OFC. No CCA anywhere in the build.

Damped and Finished

Polyfill is pre-installed to smooth the in box response, and the shell is wrapped in plush black carpet. Built in Tullahoma, Tennessee.

Enclosure Only or Loaded

Order the enclosure bare and mount your own A12, or order it loaded and we mount the driver, dress the wiring and ship it ready to bolt in.

Sealed Enclosure Performance: Pre-Calculated

Using the published Thiele Small parameters for the Arc Audio A12, here is the predicted Qtc, system resonance (Fc) and F3 rolloff for this enclosure. Calculated with the same formulas as the Audio Intensity Sealed Box Calculator.

Arc Audio A12 D2 | Qts 0.612 | Fs 25.01 Hz | Vas 76.32 L

Enclosure Size	Qtc	Fc	F3
1.00 cu ft as built	1.176	48.1 Hz	35.6 Hz

Arc Audio A12 Frequency Response | Sealed, 1.00 cu ft

1.00 cu ft (Qtc 1.176) -3dB reference

Note on coil choice: The figures above are the D2 set. The D4 A12 carries Qts 0.659 and Vas 81.81 litres, and a different Fs of 27 Hz, which in this same 1.00 cubic foot volume lands at Qtc 1.300, Fc 53.2 Hz and F3 38.4 Hz. Worth accounting for if you are choosing between the two. Run your own numbers in the Sealed Box Calculator.

Cut for the Driver, Not the Catalog

Select your configuration above. This enclosure ships free to the lower 48 with a 2 year limited warranty, built one at a time in Tullahoma, Tennessee. Ordered loaded, the A12 carries its own 1 year manufacturer warranty through authorized dealers.

Enclosure Specifications

Enclosure	Proline X M12-S ARC A, Micro Series sealed
Driver	Arc Audio A12, pre-installed
Voice Coil	Dual, available D2 or D4
Enclosure Type	Sealed
Net Internal Volume	1.0 ft³: Arc Audio's published optimum
Tuning Frequency	N/A: Sealed
Material	Langboard Elite MDF, 3/4" (18mm)
Construction	CNC-cut stack fab, dowel reinforced
External Width	28.5"
External Height	14.75"
External Depth	7.5"
Corner Geometry	3" radiused on all four corners
Subwoofer Cutout	11.1" direct fit for the A12
Max Mounting Depth	5.25"
Front Panel Thickness	1.5" double-layer stack fab
Driver Mounting	8/32 threaded inserts, stainless machine screws included
Terminal Cup	Proline X ABS/Carbon Fiber, recessed mount, stainless hardware, copper ring terminals
Wiring	Pre-wired 12g OFC speaker wire
Polyfill	Pre-installed
Finish	Plush Black automotive carpet
Built	Tullahoma, Tennessee
Warranty	2-Year Limited on the enclosure

Performance Graphs

Woofer Details

The Arc Audio A12 is the 12 inch driver in Arc's A Series: 300 watts RMS, a 5.25 inch mounting depth, and a published sealed range of 0.85 to 1.25 cubic feet with 1.0 identified as the optimum. Arc engineers the A Series for accurate, controlled bass in restricted spaces rather than maximum output, which means linear response at moderate excursion and clean integration with a front stage. It is the driver to choose when the enclosure has to disappear physically but the bass still has to do its job properly. Available in dual 2 ohm and dual 4 ohm, and like the rest of the Arc range it is dual voice coil only.

Brand + Model	Arc Audio A12
Size	12"
RMS Power	300W
Voice Coil Config	Dual 2 ohm or Dual 4 ohm
Mounting Depth	5.25"
Cutout Diameter	11.1"
Recommended Sealed Volume	0.85 to 1.25 ft³, optimum 1.0
Series	Arc Audio A Series
Driver Warranty	Through Arc Audio

Why This Combo Works

Arc Audio A12 in a Proline X 1.0 Cubic Foot Sealed Micro Series Enclosure

Arc Audio's published optimum sealed volume for the A12 is 1.0 cubic foot. That is exactly what this enclosure delivers. Their published range is 0.85 to 1.25, and building to the centre of it produces the flattest sealed response and the most controlled transient behaviour. This is not a generic box the A12 happens to fit into.

The sealed alignment suits what Arc designed the A Series to do. Linear response at moderate excursion, clean integration with a front stage, and consistent output at sustained listening levels rather than peak output for a meter reading. In a correctly sized sealed cabinet the A12 steps up output over the A10 while keeping the same character: tight, fast bass that tracks the music rather than colouring it.

At 7.5 inches deep with a 5.25 inch mounting depth, this puts a 12 inch sealed system into locations a full depth 12 cannot reach. Behind seats, against cargo panels, anywhere the available depth is decided by the vehicle rather than by you. If you have room for a standard depth 12, a standard driver in a standard box will usually give you more for the money. Shallow is a solution to a constraint.

For amplifier power, target 250 to 300W RMS at your wired impedance. D2 wired parallel gives a 1 ohm load, D4 wired parallel gives 2 ohms. The A12 is rated at 300W RMS, so a clean amplifier at that output is the correct match. Verify your amplifier's stable impedance before selecting your voice coil.

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.