Proline X
AudioControl Space SPC-12 Dual Box: Sealed 12" Shallow Down Fire Enclosure
SKU: PO 12D-S DF SPC12
- Alignment: 1.25 cu ft net per chamber, Qtc 0.74 to 0.85, F3 46.8 Hz on the SPC-12S2 (single 2 ohm) and 44.9 Hz on the SPC-12S4 (single 4 ohm)
- Drivers: Pair of AudioControl Space SPC-12 (SPC-12S2 (single 2 ohm) and SPC-12S4 (single 4 ohm)), 400 W RMS each, 9 mm Xmax, 3.94 in mounting depth
- Chambers: Two fully separate sealed chambers, 3/4" MDF full divider, one shared side-mounted terminal cup
- Standoffs: Included, 1.75 in, shipped uninstalled. Installed height near 16.56 in
- Cabinet: 30.00"W x 15.00"D x 14.81"H in down fire position, excludes standoffs, square corners
Financing available. Choose Shop Pay Installments at checkout.
AudioControl Space SPC-12 Dual Box: Sealed 12" Shallow Down Fire Enclosure
Proline X Performance Optimized Down Fire Dual 12" Sealed
Cut and tuned for a pair of AudioControl Space SPC-12
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 14.81 inches tall, the height that gives each driver its own 1.25 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 insert kit and stainless machine screws included. AudioControl publishes no bolt circle, so the inserts go in at install. | Threaded inserts, stainless machine screws included. |
| Joinery | V-groove and dado, CNC cut. | V-groove and dado, CNC cut, full-height divider and 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 a Pair of AudioControl Space SPC-12
Nothing about this cabinet is generic. The baffle is cut to 11.100 in for AudioControl's 12.370 in frame. The airspace lands on 1.25 cubic feet net per chamber, AudioControl's own recommended sealed size for this driver.
The SPC-12 is AudioControl's 12 inch Space low-profile: a fiber matrix injection-molded polypropylene cone, a weather-resistant build, a three-layer high-temperature coil former and a wrap-sealed rubber gasket, with a removable grille, rated 400 watts RMS with 9 mm of one-way excursion, 3.94 inches of mounting depth on a 12.37 inch frame. It sits 3.94 inches deep, which matters on a down fire, where the motor rises into the cabinet. Every Thiele-Small figure comes from AudioControl's own Space Series user guide, one full parameter block per coil, and each block holds together on Qts, moving mass, cone area and sensitivity. AudioControl measures the 2 ohm and 4 ohm versions as separate drivers, and they differ, so each is aligned on its own figures below.
Two Chambers, Not One Volume
This enclosure follows the Proline X standing rule for dual sealed builds: two fully separate chambers split by a bonded full height 3/4 inch MDF divider, each driver in its own 1.25 cubic feet with its own polyfill.
Two drivers sharing one sealed volume interact acoustically. Each driver's compression phase becomes the pressure environment the other is working against, which smears transient response and blurs the alignment either would have on its own. A full divider removes that entirely. One shared side mounted terminal cup feeds both driver positions, so the cabinet stays a single connection point.
Net Volume, Not Gross
Each chamber is built at 1.25 cubic feet net per driver, out of 2.70 gross after the divider and the drivers. AudioControl publishes the driver displacement, 0.0619 cubic feet, and it is taken out of the net figure for each driver.
True net, not marketing net. Internal volume is calculated from the machined cavity dimensions and the driver's displacement, not guessed from external dimensions minus wall thickness.
1.25 cubic feet net per chamber on AudioControl's published figures: the SPC-12S2 (single 2 ohm) reads Qtc 0.743 with resonance at 49.1 Hz and half power at 46.8 Hz, and the SPC-12S4 (single 4 ohm) reads Qtc 0.850 with resonance at 52.3 Hz and half power at 44.9 Hz. One cabinet serves both coils. That is AudioControl's own recommended sealed size for this driver, 1.25 cubic feet, between their 0.8 minimum and 1.7 maximum. That is a touch above maximally flat: a small lift near resonance and firm midbass.
| Driver (per chamber) | System Qtc | fc | F3 |
|---|---|---|---|
| Space SPC-12 SPC-12S2 (single 2 ohm) | Qtc 0.743 | 49.1 Hz | 46.8 Hz |
| Space SPC-12 SPC-12S4 (single 4 ohm) | Qtc 0.850 | 52.3 Hz | 44.9 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 14.81 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 16.56 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 to both driver positions. Side mounted so it stays accessible with the baffle facing the floor.
Standoffs Included
AudioControl publishes no front clearance figure for the Space SPC-12, 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 0.77 times the cone area, under the 1.0 we aim for. With 9 mm of excursion this cone moves a lot of air at its limit, so for hard use mount taller feet or run the cabinet front firing; at daily levels the slot is not the limit.
Motor Clearance and Orientation
The motors rise off the baffle into the cavity, so on a down fire cabinet the clearance that matters runs to the top panel. The 3.94 inch mounting depth puts the motor 2.44 inches into a 12.56 inch cavity, leaving 10.12 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.
AudioControl 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
AudioControl rates the Space SPC-12 at 400 watts RMS, 800 watts RMS combined. AudioControl sells the SPC-12 as SPC-12S2 (single 2 ohm) and SPC-12S4 (single 4 ohm); a matched pair should share a coil. A pair of single 2 ohm drivers lands on 1 ohm in parallel or 4 ohms in series. A pair of single 4 ohm drivers lands on 2 ohms in parallel or 8 ohms in series. Anything under 1 ohm, and many amplifiers at 1 ohm, is outside what the amplifier is built for, so series wiring is the safe default. Confirm the load against your amplifier's minimum stable impedance before powering the system.
AudioControl prints no bolt circle for the SPC-12, so the baffle ships undrilled with a threaded insert kit and stainless machine screws: set the driver in its recess, mark its holes, drill and press the inserts. The enclosure carries a 1 year limited warranty. Bring your own pair of Space SPC-12; the drivers are 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.
| Specification | Value |
|---|---|
| Series | Proline X Performance Optimized Down Fire |
| Compatible Driver | AudioControl Space SPC-12 (SPC-12S2 (single 2 ohm) and SPC-12S4 (single 4 ohm)), quantity 2. Direct fit |
| Configuration | Dual 12 inch, two separate chambers, 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 | 14.81 in in the down fire position, excludes standoffs |
| Installed Height | 16.56 in including the 1.75 in standoff |
| Internal Volume, Gross | 2.70 cu ft total |
| Internal Volume, Net Acoustic | 1.25 cu ft per chamber after the divider and the driver displacement |
| Height Set By | Airspace; clearance alone would allow a lower cabinet |
| Driver Mounting Depth | 3.94 in required, 10.12 in clearance above the motor |
| Floor Slot | 0.77 times the cone area at the 1.75 in standoff |
| Alignment, SPC-12S2 (single 2 ohm) per chamber | Qtc 0.743, fc 49.1 Hz, F3 46.8 Hz anechoic |
| Alignment, SPC-12S4 (single 4 ohm) per chamber | Qtc 0.850, fc 52.3 Hz, F3 44.9 Hz anechoic |
| Woofer Opening | 11.100 in, two, cut for AudioControl's frame |
| Frame Outer Diameter | 12.370 in |
| Bolt Circle | Not published by AudioControl; threaded insert kit included |
| Driver Displacement | 0.0619 cu ft, AudioControl spec |
| SPC-12S2 (single 2 ohm) Fs / Qts / Qes / Qms / Vas | 27.843 Hz / 0.4216 / 0.4703 / 4.0762 / 74.5578 L |
| SPC-12S4 (single 4 ohm) Fs / Qts / Qes / Qms / Vas | 30.7061 Hz / 0.4996 / 0.5764 / 3.7494 / 67.1494 L |
| Driver Sd | 511 cm2, AudioControl spec |
| Xmax | 9 mm, one-way, method not stated |
| Driver Power Handling | 400 W RMS per driver |
| Wiring Options | AudioControl sells the SPC-12 as SPC-12S2 (single 2 ohm) and SPC-12S4 (single 4 ohm); a matched pair should share a coil. A pair of single 2 ohm drivers lands on 1 ohm in parallel or 4 ohms in series. A pair of single 4 ohm drivers lands on 2 ohms in parallel or 8 ohms in series. Anything under 1 ohm, and many amplifiers at 1 ohm, is outside what the amplifier is built for, so series wiring is the safe default. |
| Parameter Source | AudioControl Space Series user manual |
| 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 | Full-height 3/4 in divider |
| Driver Mounting | Threaded insert kit and stainless machine screws included; inserts set at install, no bolt circle is published |
| Terminal Cups | One Proline X ABS and carbon fiber composite, side mounted, pre wired 12 gauge OFC to both driver positions |
| Standoffs | Included, 1.75 in, shipped uninstalled |
| Damping | Light polyfill wall lining in both chambers, does not alter acoustic volume |
| Carpet | Plush black |
| Shipping Weight | 51 lb |
| Warranty | 1 Year Limited |
| Built In | Tullahoma, Tennessee |
01Is it a sealed driver?
Efficiency bandwidth product places the motor before anything else is decided.
02What the box does to it
1.25 cu ft against a 74.6 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 9.0 mm — and a bigger one once a subsonic filter stops it wasting travel below the passband.
| Param | Value | Unit | Note |
|---|---|---|---|
| Fs | 27.84 / 30.71 | Hz | free-air resonance |
| Qts | 0.422 / 0.500 | SPC-12S2 / SPC-12S4 | |
| Vas | 74.56 / 67.15 | L | equivalent compliance |
| Sd | 511.0 | cm² | effective piston area |
| Xmax | 9 | mm | one-way, method not stated |
| Pe | 400 | W | continuous RMS |
| SPL | 87.2 | dB | 1 W / 1 m, derived from T/S |
Driver parameters as published by AudioControl user manual. 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.
Shop By Series
