Proline X
Performance Optimized Down Fire Sealed Dual 10" Enclosure | Diamond Audio DMD-SH
SKU: PO 10D-S DF DMD
- Alignment: 0.80 cu ft net per chamber. Qtc 0.856 (D2), Qtc 0.981 (D4) per driver
- Chambers: Two fully separate sealed chambers, 3/4" MDF full divider, one shared side-mounted terminal cup
- Drivers: Pair of Diamond DMD102SH or DMD104SH, 250W RMS each, 3.00" mounting depth
- Cabinet: 30"W x 15"D x 10.125"H measured in down fire position, square corners
Financing available. Choose Shop Pay Installments at checkout.
Performance Optimized Down Fire Sealed Dual 10" Enclosure | Diamond Audio DMD-SH
Proline X Performance Optimized Down Fire Dual 10" Sealed
Cut and tuned for a pair of Diamond Audio DMD-SH 10s
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. 24.5 by 13.5 inches on the 10 inch. | Shared 30 by 15 inch platform on most builds, with cabinet height as the variable. A few drivers need a wider or deeper platform. | Compact per driver footprint. 21.5 by 14.5 inches on the 10 inch. |
| 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. | 8/32 threaded inserts, stainless machine screws included. | 8/32 threaded inserts, stainless machine screws included. |
| Joinery | V-groove and dado, CNC cut. | V-groove and dado, CNC cut, 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 Diamond Audio DMD-SH 10's own published numbers. A Performance box fits your subwoofer. A Performance Optimized box was built for it.
Built Around a Pair of DMD-SH 10s
Nothing about this cabinet is generic. Both baffle positions are bored to the driver's 9.13 inch cutout, the internal height is set by its 3.00 inch mounting depth, and the two driver positions sit side by side on a 30 by 15 inch footprint. The finished cabinet stands 10.125 inches tall measured in the down fire position, which makes it a cargo floor or rear wall build rather than an under seat one.
Each DMD-SH is a shallow mount design: an aluminum heatsink dust cap over a high strength paper cone, a die-cast shallow frame, a vented pole for cooler operation, oversized push terminals, a black spider with woven tinsel leads, and a wrap-around ABS mounting gasket. Diamond states that the motor and suspension symmetry are Klippel optimized.
The two coil variants sit further apart than most dual impedance pairs. The DMD102SH, dual 2 ohm, runs a Qts of 0.66 with 13.7 T of motor force and 7.9mm of Xmax. The DMD104SH, dual 4 ohm, runs a Qts of 0.77 with 16.4 T and 8.8mm. Buy a matched pair and wire both drivers identically, since mismatched wiring between chambers splits power unevenly.
Net Volume, Not Gross
Total internal gross volume is 1.646 cubic feet, split by the divider into 0.80 cubic feet net per driver, 1.60 cubic feet net total. That is the same per driver alignment as the single driver cabinet, so this is identical character with twice the cone area behind it and roughly 6 dB more maximum output.
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.
Each chamber is larger than Diamond's suggested 0.45 cubic feet per driver, a figure that puts the D2 near Qtc 0.98 and the D4 above 1.14, both underdamped. At 0.80 net per chamber the DMD104SH lands at Qtc 0.981 with F3 at 52.4 Hz and the DMD102SH at Qtc 0.856, with 2 to 3 Hz more extension than Diamond's own volume gives. Their manual presents its enclosure table as a suggestion rather than a specification.
These figures are computed from the Thiele-Small parameters Diamond publishes, and they do not match the Qtc values printed in Diamond's enclosure table, which run lower by roughly 0.2 to 0.3 across every variant. No gross versus net convention closes a gap that size, so we publish the figure that follows from the driver data. Free-air resonance is 48.0 Hz on the D2 and 48.5 Hz on the D4, which is why F3 lands in the low 50s in any sealed volume.
Down Fire Construction
Cut with V-groove and dado joinery 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 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.
Double Baffle, Flush Recess
The front baffle is 1.5 inches at both driver positions, two bonded 3/4 inch sheets, with the outer layer machined as a flush recess so each driver bolts to the inner layer. That recovers 3/4 inch of internal clearance. Two sets of 8/32 threaded inserts and stainless machine screws are included.
Side-Mounted Terminal Cup
One shared 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 in parallel. Side mounted so it stays accessible with the baffles facing the floor.
Separate Chambers
A full height 3/4 inch MDF divider is bonded in, giving each driver its own sealed 0.80 cubic feet and its own polyfill. Perimeter cross-bracing ties the long spans together on both sides of the divider.
Why Two Chambers, Not One
Separate chambers are the standing design rule on every Proline X dual sealed enclosure. 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 driver would have on its own.
A full height bonded divider removes that interaction. Each DMD-SH gets its own dedicated airspace, its own damping, and its own clean sealed alignment. The cost is one panel and a fraction of a cubic foot; the benefit is that the pair behaves like two correct single driver cabinets sharing a footprint.
Both drivers fire downward into the floor and the cabinet couples to the surface it sits on. No standoffs are required. The sealed rolloff meets rising cabin gain below 60 Hz, so in-car response extends well below the anechoic figures quoted above.
Power and Warranty
Each DMD-SH 10 is rated 250 watts RMS and 500 watts maximum, so the pair takes 500 watts RMS combined. Both variants are dual voice coil and the single cup feeds both positions in parallel, so the final load is set at the drivers. Wire the two identically and confirm the result against your amplifier's minimum stable impedance before powering the system.
The enclosure carries a 1 year limited warranty. Bring your own pair of DMD102SH or DMD104SH; the drivers are purchased separately.
Cut for the Driver, Not the Catalog
Two chambers, two alignments worked out from the published parameters instead of a table of round numbers, one footprint. Machined, assembled and inspected one at a time in Tullahoma, Tennessee.
| Series | Proline X Performance Optimized Down Fire |
| Compatible Driver | Diamond Audio DMD102SH (DVC 2Ω) or DMD104SH (DVC 4Ω) | Pair Required |
| Enclosure Type | Sealed | Dual Driver | Down Fire Geometry | Floor-Coupled |
| Chamber Configuration | Two Fully Separate Chambers | Full Divider | Single Shared Side-Mounted Terminal Cup |
| Firing Direction | Down Firing, Both Drivers Fire Toward Floor |
| External Width | 30 Inches |
| External Depth | 15 Inches |
| External Height | 10.125 Inches |
| Dimension Reference | All External Dimensions Measured In Down Fire Position |
| Total Internal Gross Volume | 1.646 Cubic Feet |
| Per-Chamber Net Volume | 0.80 Cubic Feet |
| Total Net Volume | 1.60 Cubic Feet |
| Diamond Suggested Sealed Volume | 0.45 Cubic Feet Gross Per Driver (We Build Larger, See FAQ) |
| Target Qtc Per Chamber (DMD104SH) | 0.981 (Computed from Published T/S) |
| Predicted F3 Per Driver (DMD104SH) | 52.4 Hz |
| Driver Fs | 48.0 Hz (D2) / 48.5 Hz (D4) |
| Driver Qts | 0.66 (D2) / 0.77 (D4) |
| Driver Vas | 15.4 Liters (D2) / 15.8 Liters (D4) |
| Driver BL | 13.7 T (D2) / 16.4 T (D4) |
| Driver Xmax | 7.9mm (D2) / 8.8mm (D4) |
| Power Handling | 250 Watts RMS Each / 500 Watts RMS Combined |
| Mounting Depth Required | 3.00 Inches (Diamond Spec) |
| Woofer Opening (Cutout, Each) | 9.13 Inches (Diamond Spec) |
| Standoffs | None Required |
| 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 | Double-Layer 1.5" MDF at Both Driver Positions |
| Chamber Divider | 3/4" MDF Full Bonded Panel |
| Corner Profile | Square (Down Fire Series Standard) |
| Driver Mounting | 8/32 Threaded Inserts | Stainless Steel Machine Screws Included | 2 Sets |
| Terminal Cup | One Proline X ABS/Carbon Fiber Composite | Side Mounted |
| Internal Wiring | 12 Gauge OFC, Pre-Wired to Both Driver Positions |
| Damping | Polyfill Pre-Installed Per Chamber |
| Carpet | Plush Black |
| Voice Coil Configuration | Dual Voice Coil Per Driver, Final Impedance Set At The Drivers |
| Bundle Options | Enclosure Only (Bring Your Own Pair of DMD102SH or DMD104SH) |
| Weight | 44 lb |
| Warranty | 1-Year Limited (Enclosure) |
| Built In | Tullahoma, Tennessee, USA |
01Is it a sealed driver?
Efficiency bandwidth product places the motor before anything else is decided.
02What the box does to it
0.80 cu ft against a 15.8 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 8.8 mm — and a bigger one once a subsonic filter stops it wasting travel below the passband.
| Param | Value | Unit | Note |
|---|---|---|---|
| Fs | 48.50 | Hz | free-air resonance |
| Qts | 0.770 | D4 | |
| Vas | 15.80 | L | equivalent compliance |
| Sd | 359.0 | cm² | effective piston area |
| Xmax | 8.8 | mm | one-way linear travel |
| Pe | 250 | W | continuous RMS |
| SPL | 85.2 | dB | 1 W / 1 m, derived from T/S |
Driver parameters as published by diamondaudio.com product page. 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
