Proline X
Proline X Micro Series 12" Sealed Enclosure - Fits Arc Audio SW12
SKU: M12-S ARC Medium Enclosure Only
- Fits: Arc Audio SW12 | 2.4" Shallow-Mount | Motor Outside Sealed Volume
- Net Volume: 0.65 / 0.8 / 1.0 cu ft | Shared 26" x 14.75" Footprint
- Orientation: Down-Fire Primary, Front-Fire Secondary | 4-Foot Kit Included
- Build: Stack-Fab Langboard Elite MDF | 3" Radiused Corners | Pre-Wired 12g OFC
Financing available — choose Shop Pay Installments at checkout.
Proline X Micro Series 12" Sealed Enclosure - Fits Arc Audio SW12
Proline X Micro Series 12" Sealed Enclosure
Cut, layered, and tuned for the Arc Audio SW12 shallow-mount subwoofer
Built Around the Arc Audio SW12
This is not a generic 12-inch box with a label on it. Every layer is cut to the Arc Audio SW12's published sealed targets, with the baffle bored to the SW12's 11-inch cutout and 8/32 threaded inserts set on the back face for tool-clean machine-screw mounting. The SW12 is a 2.4-inch shallow-mount driver built for deep, controlled bass in tight spaces, and this enclosure is the matched airspace it was designed to live in.
The SW12 carries Arc Audio's published Thiele-Small data: Fs of 33 Hz, Qts of 0.616, Vas of 33.73 liters, and an EBP of 45.9, which places it firmly in sealed-enclosure territory. We ran the alignment math on that data and built the box to land it where it belongs. The larger Vas means the SW12 wants more airspace than the SW10 to reach the same Qtc, which is why these boxes run deeper.
One Footprint, Three Net Volumes
All three sizes share the same 26 by 14.75 inch face. Only the depth changes, so the box keeps the same mounting footprint whether you want the tightest response or the most extension. The volume you select is true net internal airspace, measured after the layered walls, bracing, and driver are accounted for. It is not a gross number with the losses hidden.
Minimum | 0.65 cu ft net
26 x 14.75 x 5.25 in. The lowest-profile build with a warm, slightly boosted character. The right call when depth clearance is the hard limit.
Optimum | 0.8 cu ft net
26 x 14.75 x 6.75 in. Arc Audio's recommended sealed volume. The balanced alignment, with controlled low end and clean transient response.
Maximum | 1.0 cu ft net
26 x 14.75 x 8.25 in. The lowest Qtc of the three for the flattest response and deepest extension, when you have the room to give it.
Down-Fire First, Front-Fire When You Need It
This box is designed primarily to fire down. A separate 4-foot kit is included so you can lift the enclosure off the floor when you mount it down-fire, which sets the gap the cone loads against, couples the bass into the chassis, and protects the driver face. Install the feet when you run it down-fire, leave them off when you do not. It also works front-fire as a secondary orientation if your space calls for it, so the same box covers both installs.
The SW12 helps here because its N42UH neodymium motor sits outside the sealed air volume. In a down-fire box that motor lives in the open cavity between the baffle and the floor rather than crammed inside a hot, sealed pocket, so it gets free airflow on every excursion. It also means the net airspace stays true, since the motor is not stealing volume from inside the chamber. We do not mill a magnet-relief pocket the way we do on rear-motor drivers, because there is no rear motor to relieve. The chamber is clean, sealed, and built only for the cone.
True net, not marketing net. Internal volume is calculated by summing each CNC-cut layer's opening. Dowel reinforcement runs between layers purely as tension hardware and does not reduce the airspace you paid for.
Proline X Stack-Fab Construction
Every Micro Series enclosure is cut 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. Instead of butt joints or dado cuts, the box is stack-fabricated: each layer is a precision-cut ring, and the stacked layers do the joining themselves. The result is a continuous, void-free wall with no seam to flex or leak.
Radiused, Not Boxy
All four corners are radiused 3 inches viewed top-down. Cleaner airflow inside, and a finished look that does not telegraph a slab-sided box under the carpet.
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 in every sealed build 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 drop in your own Arc Audio SW12, or order it loaded and we mount the driver, dress the wiring, and ship it ready to bolt in. Loaded builds are available in both the SW12 D2 and SW12 D4 coil configurations, selectable by variant. Either way the box is the same precision-cut shell, cut to the size you select, and the 4-foot down-fire kit is included so you are ready to run it either orientation out of the box.
Sealed Enclosure Performance: Pre-Calculated
Using Arc Audio's published Thiele-Small parameters for the SW12 in the D4 parallel configuration, here are the predicted Qtc, system resonance (Fc), and F3 rolloff across the three sizes this enclosure is offered in. Arc Audio recommends 0.8 cubic feet as the optimum sealed volume. These are calculated with the same formulas as the Audio Intensity Sealed Box Calculator.
| Enclosure Size | Qtc | Fc | F3 |
|---|---|---|---|
| Minimum | 0.65 cu ftTightest profile, warm and slightly boosted | 1.037 | 55.5 Hz | 43.0 Hz |
| Optimum | 0.80 cu ft ★Arc Audio recommended sealed volume | 0.972 | 52.1 Hz | 41.5 Hz |
| Maximum | 1.00 cu ftFlattest response, deepest extension | 0.912 | 48.8 Hz | 40.2 Hz |
Arc Audio SW12 Frequency Response | Sealed
Note on impedance: These alignments are calculated from Arc Audio's published T/S for the SW12 in the D4 parallel set. The D2 variant carries slightly different Qts and Vas figures and will land marginally different sealed alignments, though all three sizes stay in the same character range. Run your own numbers in the Sealed Box Calculator.
Cut for the Driver, Not the Catalog
Select your size and configuration above. Every Proline X Micro Series enclosure ships with free shipping to the lower 48 and a 2-year warranty, built one at a time in Tullahoma, Tennessee.
| Proline X Micro Series 12" Sealed Enclosure Specifications | |
|---|---|
| Series | Proline X Micro Series |
| Enclosure Type | Sealed |
| Firing Orientation | Down-fire primary, front-fire secondary |
| Included Hardware | 4-foot down-fire kit (installed as needed) |
| Driver Fitment | Arc Audio SW12 (D2 or D4) |
| Baffle Cutout | 11 in, bored for the Arc Audio SW12 |
| Net Internal Volume | 0.65 / 0.8 / 1.0 cu ft (true net, selectable by size) |
| External Dimensions | 26 x 14.75 x 5.25 in (0.65) / 26 x 14.75 x 6.75 in (0.8) / 26 x 14.75 x 8.25 in (1.0) |
| Mounting Footprint | 26 x 14.75 in (shared across all three sizes) |
| Material | Langboard Elite 3/4 in MDF (48.5 lb/ft³, 200 psi internal bond, 410,000 psi MOE) |
| Construction | Stack-fabricated on ShopSabre CNC, dowel tension reinforcement |
| Corner Radius | 3 in, all four corners (viewed top-down) |
| Driver Mounting | 8/32 threaded inserts on baffle back face, machine screws included |
| Terminal Cup | Proline X ABS / carbon-fiber composite, stainless hardware, copper ring terminals, pre-wired 12-gauge OFC |
| Damping | Polyfill pre-installed |
| Finish | Plush black carpet |
| Configurations | Enclosure only / Loaded SW12 D2 / Loaded SW12 D4 |
| Build Location | Tullahoma, Tennessee |
| Warranty | 2-year limited |
| Shipping | Included to the lower 48 |
Built From a Spec Sheet, Not a Sales Sheet
Every Proline X Micro 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 across the 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 — 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 stack-fab layering 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 Micro 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.