Proline X PO12D-S SI | Dual 12" Sealed Subwoofer Enclosure | Built for Stereo Integrity SQL

Performance Optimized | Dual Stereo Integrity SQL 12 Dual 12" Sealed Enclosure | Isolated Chambers | Dual Mounting Face for the SQL 12 Series 2 2.0 ft³ Net Total Isolated Chambers 1.0 ft³ Per Chamber 31" × 15" × 13.625" Double Baffle V-Groove / Dado Built in Tennessee Two Stereo Integrity SQL 12s, Each in Their Own Engineered Chamber The Performance Optimized Dual Sealed 12 for the Stereo Integrity SQL 12 is a fully chambered sealed enclosure engineered around a pair of SQL 12 Series 2 subwoofers. Two isolated 1.0 cubic foot chambers, separated by a center divider, each tuned to the SQL 12's published Thiele-Small parameters. Dual mounting face design gives each driver its own dedicated baffle. No shared airspace, no acoustic crosstalk between drivers, no compromise from doubling up in a common chamber. This is not the same construction as our common-chamber PO duals. The SQL 12 is a serious high-power driver — 1000 watts RMS per unit, 26mm one-way linear Xmax, and enough motor force to move meaningful air. At those power and excursion levels, isolated chambers stop being nice-to-have and become the correct engineering answer. Each SQL 12 operates in its own dedicated acoustic environment, unaffected by what the other driver is doing at any given moment. Each SQL 12 gets its own sealed 1.0 cubic foot chamber — the maximum sealed volume Stereo Integrity specifies for the SQL 12 Series 2. The chambered design means each driver operates as if it were in its own dedicated single enclosure, with a center divider that also serves as structural bracing. Why Isolated Chambers Matter at This Power Level For lower-power dual subwoofer systems in the 300-500 watt per driver range, a common chamber works fine. Matched driver pairs load symmetrically, and shared airspace introduces minimal interaction. At the SQL 12's 1000 watt RMS per driver rating, the calculation changes. Higher power means more cone excursion, more thermal load, and more asymmetric behavior between the two drivers as they respond to different thermal and mechanical states in real time. Isolated chambers eliminate that variable entirely. Symmetric Loading Under Real Power Each SQL 12 operates against its own dedicated 1.0 cubic foot airspace. If one driver's voice coil resistance rises from heat faster than the other, or if one driver breaks in at a slightly different rate, the pair still performs consistently because they aren't coupled through shared air. Force Cancellation Benefits The dual mounting face design creates opposing forces that partially cancel through the cabinet structure. Less mechanical energy transferred to the vehicle chassis, less rattle in trim panels, and cleaner perceived output because the cabinet itself is doing less unwanted work. Structural Rigidity The center divider acts as a full-length brace in addition to its acoustic role. The 31" cabinet width is split into two 15.5" panel sections structurally, dramatically reducing panel flex compared to an unbraced wide interior at the power levels the SQL 12 delivers. Predictable Behavior at Full Excursion The SQL 12's 26mm one-way Xmax means significant air displacement per stroke. Isolated chambers guarantee each driver's air spring stays consistent through the full excursion range, without pressure variations from the second driver influencing the first. Engineered Around the SQL 12's Parameters Stereo Integrity specifies the SQL 12 Series 2 for sealed enclosures between 0.65 and 1.0 cubic feet per driver. The Performance Optimized Dual Sealed 12 delivers 1.0 cubic foot per chamber — the upper end of SI's specified range, where the SQL's deep low-end extension characteristics fully develop. In a properly sized cabinet, the SQL 12 plays down to F3 points in single-digit territory, delivering the low-frequency response that makes SI's SQL series unmatched at its price point. Volume Selection 1.0 cubic foot per chamber is the maximum of SI's recommended sealed volume range. Smaller volumes tighten Qtc and lose some low-end extension. Larger volumes fall outside SI's specification and compromise transient control. 1.0 cubic foot per driver is where the SQL 12 delivers on its full low-end capability while staying inside the driver's engineered operating window. Mounting Geometry Both baffles are cut to the SQL 12's exact 11.33" cutout specification and doubled to 1.5" total thickness at the mounting position. The SQL 12's 7" mounting depth leaves comfortable internal clearance inside the 13.625" deep cabinet. Each driver has its own dedicated mounting face — a true dual-face design that separates the two drivers acoustically and mechanically, with 8/32 threaded inserts pressed into the doubled baffle stock for secure, full-depth mounting. Performance Series Construction, Driver-Specific Tuning Double Baffle Mounting Faces Each of the two mounting faces uses a doubled 1.5" total baffle thickness — two layers of 3/4" Langboard Elite MDF bonded together at the driver mounting position. Doubled baffle stock resists baffle flex and mounting screw pullout at the power levels the SQL 12 delivers. 8/32 Threaded Inserts Into Double Baffle Both baffles use 8/32 threaded inserts pressed into the doubled 1.5" MDF backside, providing full-depth thread engagement for the supplied stainless steel mounting screws. No stripped pilot holes, no MDF damage from drywall screws, and secure retention at high excursion levels. V-Groove and Dado Joinery CNC-cut V-grooves at every panel intersection let the cabinet fold into shape with maximum glue surface. Dado joints lock the doubled baffles, rear panel, and center divider into the side walls — no fasteners visible from outside, no exposed end grain at joints. Pre-Wired Terminal Cups (×2) One Proline X ABS/carbon fiber composite terminal cup per chamber, each pre-wired with 12-gauge OFC. Wire each driver to its own amp channel for maximum control, or jumper the cups externally for a single-channel pair. Every panel is cut on ShopSabre CNC routers in our Tullahoma, TN facility. The center divider is dadoed into the top, bottom, and rear panels for maximum mechanical lock — not just glued in. Both mounting baffles are doubled to 1.5" total thickness at the mounting positions. Internal volume is verified per chamber on every unit. Customize Your Build Carpet Finish Dark Gray Trunkliner is the standard durable wrap, matched to most factory trunk and cargo-area carpet tones. Plush Black (+$10) is a deeper, more luxurious nap that pairs well with blacked-out interiors and show builds. Acrylic Insert Color Choose Black, Blue, Red, or White for the baffle inserts to match your build. Or skip the inserts entirely (-$40) for a clean, understated look. The inserts are purely cosmetic — performance is identical across colors. Box-Only or Loaded Pair Add a matched pair of Stereo Integrity SQL 12 Series 2 drivers directly to your order in Dual 2-ohm or Dual 4-ohm and Paper or Carbon Fiber dust cap configurations. Already own your SQL 12s? Order the enclosure box-only and drop in the drivers you have. Wiring Two SQL 12s to Your Amplifier Each chamber has its own dedicated terminal cup, pre-wired with 12-gauge OFC. The two cups can be jumpered externally for a single-amp installation, or wired independently for dual monoblock or multi-channel amplifier setups. Two Dual 2-Ohm SQL 12s Each driver's coils in parallel = 1 ohm per driver. Two 1-ohm drivers in parallel = 0.5 ohm combined (most monoblocks won't handle this — verify your amp). Two 1-ohm drivers in series = 2 ohms combined. Each driver on its own monoblock at 1 ohm gives you the cleanest high-power setup. Two Dual 4-Ohm SQL 12s Each driver's coils in parallel = 2 ohms per driver. Two 2-ohm drivers in parallel = 1 ohm combined. Two 2-ohm drivers in series = 4 ohms combined. Dual 4-ohm is the more flexible option for most amplifier setups at these power levels. The SQL 12 pair is rated for 2000 watts RMS combined. Aim for a clean, well-regulated amplifier or amplifier pair delivering 1500 to 2000 watts total at your chosen impedance. At this power level, amplifier quality matters more than headline numbers — regulated power supply, low THD, and honest RMS ratings. Built in Tennessee, Backed by Audio Intensity Every Performance Optimized enclosure is CNC-cut, assembled, and finished in our Tullahoma, TN facility. Components are pulled from inventory after your order is placed, then bonded and wrapped — a 2 to 5 business day assembly window before the box ships. No pre-built inventory sitting in warehouses, warping in storage. Each unit is built to order. Backed by a 1-year limited warranty against structural failure and hardware defects. Questions on fitment, wiring, or amplifier pairing? Contact us — we install this gear ourselves, in our own vehicles. Two SQL 12s, Engineered Correctly Isolated chamber design, dual mounting face, driver-specific 1.0 cubic foot chambers, and Performance Series construction built for the power levels the SQL 12 delivers. The correct cabinet for a serious pair of SIs.