Proline X
Performance Optimized Down Fire Sealed 10" Enclosure | Hertz Mille Pro MP 250
SKU: PO 10-S DF MP
- Alignment: 1.00 cu ft net, Qtc 0.741, Fc 41.2 Hz, F3 39.4 Hz, better damped than Hertz's own 0.60 recommendation
- Driver: Hertz MP 250 D2.3 or D4.3, 600W RMS / 1200W peak, 17mm Xmax, 5.80" mounting depth, 3.2 L displacement
- Fitment: 236mm cutout, 3/8" milled magnet relief, double-layer 1.5" front baffle with flush outer recess
- Build: Proline X V-groove and dado joinery, perimeter cross-brace, 12g OFC side-mounted terminal cup
- Cabinet: 30"W x 15"D x 7.4375"H measured in down fire position, square corners
Financing available — choose Shop Pay Installments at checkout.
Performance Optimized Down Fire Sealed 10" Enclosure | Hertz Mille Pro MP 250
Proline X PO Down Fire 10" Sealed
Cut and tuned for the Hertz Mille Pro MP 250
Built Around the Hertz MP 250
Nothing about this cabinet is generic. The baffle is bored to the MP 250's 236mm cutout, the internal height is set by its 5.80 inch mounting depth, and the airspace is what that geometry leaves once the driver is in place. Overall frame diameter is 268mm, and the driver bolts to 8/32 threaded inserts with stainless machine screws included.
The construction is classic Hertz. The cone is a V-cone profile pressed from paper pulp with mineral powder injection, the same technique used on the flagship Mille Legend line, so the diaphragm resists bending and behaves like a piston instead of flexing at the outer edge as excursion rises. The surround is high-purity IIR butyl rubber. Motor work is a 65mm four-layer CCAW voice coil on a vented TIL-P former, carried in a six-spoke aluminum alloy basket with vents under the spider.
Excursion is 17mm linear with 27mm of mechanical travel before damage, so there is real headroom above the linear figure. Sensitivity is 83.4 dB at 1W/1m, which is on the low side for a 10 inch driver, so plan on giving it power rather than expecting output from a small amplifier. One clarification if you are cross shopping: the Mille Pro MPS 250 is the shallow mount driver and gets its own shorter cabinet. This page is cut for the deeper, higher excursion MP 250 only.
Net Volume, Not Gross
We build this cabinet at 1.00 cubic feet net against 1.11 gross, and Hertz publishes 17 liters, or 0.60 cubic feet, as the recommended sealed volume. The gap is driver geometry, not preference. At 5.80 inches the MP 250 is a deep driver, and it displaces 3.2 liters, 0.113 cubic feet, of airspace on its own. Even with the flush recess outer baffle layer and a milled magnet relief recovering clearance, the minimum internal height works out to 5.1875 inches. A 0.60 cubic foot cabinet cannot physically contain this driver.
True net, not marketing net. Internal volume is calculated from the machined cavity dimensions and the driver's published displacement, not estimated from external dimensions minus wall thickness.
The constraint improves the alignment. Computed from Hertz's published Fs of 30 Hz, Qts of 0.54 and Vas of 25 liters, this cabinet lands at Qtc 0.741 with Fc at 41.2 Hz and a predicted F3 of 39.4 Hz. At Hertz's own 0.60 cubic feet the same driver computes to Qtc 0.849 with F3 at 40.6 Hz. The larger box is better damped, holds transients tighter, and reaches marginally deeper.
The MP 250 D2.3 and MP 250 D4.3 share the same Thiele-Small set, so the alignment above applies to both. The only difference is coil impedance, which you set at the driver, not a difference in enclosure behavior.
Firing down into the floor, the sealed rolloff meets rising cabin gain below 60 Hz, so in-car response extends below the anechoic figure.
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. Perimeter cross-bracing ties the panels together and polyfill is pre-installed. Corners are square on Down Fire cabinets.
External dimensions are 30 inches wide by 15 inches deep by 7.4375 inches tall, measured in the down fire position. The driver fires down into the floor, and the finished weight is 30 pounds.
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. Side mounted so it stays accessible with the baffle facing the floor.
Milled Magnet Relief
A 3/8 inch deep relief is machined into the panel opposite the baffle, directly behind the magnet. That buys back clearance for the MP 250's motor without adding cabinet height.
Power and Warranty
Hertz rates the MP 250 at 600 watts RMS and 1200 watts peak. Both versions are dual voice coil, so final impedance is set at the driver: the D2.3 gives 1 ohm in parallel or 4 ohms in series, the D4.3 gives 2 ohms in parallel or 8 in series. Confirm your amplifier is stable at your chosen load before powering the system.
The enclosure carries a 1 year limited warranty. Bring your own Hertz Mille Pro MP 250 D2.3 or MP 250 D4.3; the driver is purchased separately. The cutout, mounting depth and magnet clearance are all cut for that driver specifically.
Cut for the Driver, Not the Catalog
One driver, one set of published parameters, one cabinet machined to match them. Built one at a time in Tullahoma, Tennessee.
| Series | Proline X Performance Optimized Down Fire |
| Compatible Driver | Hertz Mille Pro MP 250 D2.3 or MP 250 D4.3 |
| Enclosure Type | Sealed | Down Fire Geometry | Floor-Coupled |
| Firing Direction | Down Firing, Driver Fires Toward Floor |
| External Width | 30 Inches |
| External Depth | 15 Inches |
| External Height | 7.4375 Inches |
| Dimension Reference | All External Dimensions Measured In Down Fire Position |
| Internal Volume (Gross) | 1.11 Cubic Feet |
| Internal Volume (Net After Displacement) | 1.00 Cubic Feet |
| Hertz Recommended Sealed Volume | 17 Liters / 0.60 Cubic Feet (See FAQ On Why This Cabinet Is Larger) |
| Target System Qtc | 0.741 (Hertz Volume Computes To 0.849) |
| Predicted Fc | 41.2 Hz |
| Predicted F3 | 39.4 Hz |
| Driver Fs | 30 Hz |
| Driver Qts | 0.54 |
| Driver Qes / Qms | 0.60 / 5.92 |
| Driver Vas | 25 Liters / 0.883 Cubic Feet |
| Driver Re (Series) | 3.4 Ohm |
| Driver Le | 2.6 mH |
| Driver BL | 14.2 N/A (Series) |
| Driver Mms | 182 g |
| Driver Sd | 355 cm² (213mm Effective Diameter) |
| Driver Xmax | 17mm Linear |
| Driver Xmech | 27mm Before Damage |
| Driver Displacement | 3.2 Liters / 0.113 Cubic Feet |
| Driver Sensitivity | 83.4 dB (1W/1m) |
| Driver Power Handling | 600 Watts RMS / 1200 Watts Peak |
| Driver Voice Coil | 65mm CCAW | 4-Layer | Vented TIL-P Former |
| Driver Cone | V-Cone Profile | Pressed Paper Pulp with Mineral Powder Injection |
| Driver Surround | High-Purity IIR Butyl Rubber |
| Driver Basket | Six-Spoke Aluminum Alloy with Vents Under Spider |
| Driver Overall Diameter | 268mm / 10.551 Inches (Hertz Spec) |
| Mounting Depth Required | 5.80 Inches (Hertz Spec) |
| Woofer Opening | 236mm / 9.291 Inches (Hertz Spec) |
| Standoffs | Not Required On This Build |
| Material | Langboard Elite 3/4" MDF |
| Construction | ShopSabre CNC / Perimeter Cross-Brace |
| Joinery | V-Groove and Dado (CNC-Cut) |
| Panel Thickness | 3/4 Inch |
| Front Baffle Construction | Double-Layer 1.5" MDF | Outer Layer Flush Recess, Driver Mounts To Inner Layer |
| Magnet Relief | 3/8" Deep Milled Relief In Opposite Panel |
| Corner Profile | Square (Down Fire Series Standard) |
| Driver Mounting | 8/32 Threaded Inserts | Stainless Steel Machine Screws Included |
| Voice Coil Configuration | Dual Voice Coil, Impedance Set At The Driver |
| Terminal Cup | Proline X ABS/Carbon Fiber Composite | Side Mounted | 12g OFC Pre-Wired |
| Internal Wiring | 12 Gauge OFC |
| Damping | Polyfill Pre-Installed |
| Carpet Finish | Dark Gray Trunkliner (Standard) or Plush Black |
| Weight | 30 lb |
| Bundle Options | Enclosure Only (Bring Your Own Hertz MP 250) |
| Warranty | 1-Year Limited (Enclosure) |
| Built In | Tullahoma, Tennessee, USA |
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
