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Proline X PO 12T-S W DMD sealed wedge enclosure, product photos pending. Placeholder graphic reading Photos Coming Soon.

Performance Optimized · Datasheet

Performance Optimized Wedge Wide Sealed Triple 12" Enclosure Diamond Audio DMD-SH · Triple 12" Sealed enclosure

Net volume
1.974 cu ft per driver, 5.92 cu ft total, after both dividers and an estimated 0.048 cu ft displacement per driver
Max mounting depth
3.00 in required; 13.51 in clearance above the motor against the raked rear panel
External dimensions
44 in W × 17 in at the seat face H × 23.00 in at the base D
Front baffle
1.5 in double baffle, outer layer machined as a flush recess
Buy at Audio IntensityFactory-direct, ships from Tullahoma
Diamond Audio DMD-SHBuy at Audio Intensity
  • Best For: Triple Diamond Audio DMD-SH SUV Cargo-Floor Builds
  • Net Volume: 1.974 cu ft per Driver (5.92 cu ft Net Total)
  • Driver Match: Three Diamond Audio DMD-SH (Dual 2 Ohm), matched
  • Construction: 3 Chambers | 44" Wide Wedge | V-Groove/Dado | Double 1.5" Baffle | 3 Terminal Cups

Spec of record

Technical specifications

SpecificationValue
SeriesProline X Performance Optimized Wedge Wide
Compatible DriverDiamond Audio DMD-SH, quantity 3, matched. Direct fit
ConfigurationTriple 12 inch sealed wedge, 3 chambers, 1 driver per chamber
Mounting PositionSUV cargo floor, raked face against the rear seat back
Firing DirectionRearward toward the liftgate. Not a down fire design
External Width44 in
External Height17 in at the seat face
External Depth23.00 in at the base, tapering to 16.81 in at the top
Internal Volume, Gross6.29 cu ft total
Internal Volume, Net Acoustic1.974 cu ft per driver, 5.92 cu ft total, after both dividers and an estimated 0.048 cu ft displacement per driver
Driver Mounting Depth3.00 in required; 13.51 in clearance above the motor against the raked rear panel
Alignment Per DriverDMD122SH DVC 2ohm Qtc 0.958, fc 57.3 Hz, F3 45.9 Hz anechoic
Woofer Openings3 at 11.060 in
Woofer LayoutOne row across the face
Frame Outer Diameter12.83 in
Fs / Qts / Qes / Qms46.0 Hz / 0.770 / 0.840 / 9.000
Vas / Sd / Xmax30.7 L / 539 cm2 / 8 mm
Driver Power Handling300 W RMS per driver, 900 W RMS for the set of 3 (thermal rating)
Recommended Amplifier130-190 W RMS per driver, 390-570 W RMS for the full set, at 3 ohms
Parameter SourceDiamond Audio published specifications
MaterialLangboard Elite MDF
ConstructionCNC cut, V-groove and dado joinery
Panel Thickness0.75 in
Front Baffle1.5 in double baffle, outer layer machined as a flush recess
Internal BracingTwo full-height 3/4 in dividers
Driver MountingThreaded inserts, stainless machine screws included
Terminal CupsThree Proline X ABS and carbon fiber composite, on the rear panel, one per chamber, pre wired 12 gauge OFC
Acrylic InsertGloss black acrylic baffle insert standard
DampingLight polyfill wall lining in every chamber, does not alter acoustic volume
CarpetPlush black
Shipping Weight99 lb
Warranty1 Year Limited
Built InTullahoma, Tennessee

Modelled response

Performance in this enclosure

Net airspace
1.974
cu ft per driver
System Qtc
0.96
sealed
Half power
45.9
Hz · F3
Xmax at
195
W RMS per driver · no filter
With 25 Hz subsonic
199
W RMS per driver · +2%
Amplifier, per driver
130–190
W RMS recommended
This enclosure holds 1.974 cu ft net per driver. In it the Diamond Audio DMD122SH DVC 2ohm runs a system Qtc of 0.96 with half power at 45.9 Hz, and the cone reaches its 7.9 mm travel limit at 195 W per driver, below the driver’s 300 W thermal rating, so travel is what stops you here, not heat. A 25 Hz subsonic filter adds little here: 199 W per driver against 195 W, 2 percent. The box already resonates at 57 Hz, so its own rolloff has removed most of what the filter would have stopped.

00Sizing the amplifier

Every wattage on this panel is per driver. This cabinet holds three, so the amplifier feeds all three at once.

Per driver 130–190 W RMS  ×  3 drivers  =  full set 390–570 W RMS at 3 ohms
Look for a mono amplifier rated 390–570 W RMS at 3 ohms, the load the set wires to most easily. Travel sets the top here, not heat: past 199 W per driver the cone runs beyond Xmax even with the subsonic set, under the driver’s 300 W thermal rating. Below the bottom of the range it will play, just with less headroom; above the top you are buying power the drivers cannot use.

01Is it a sealed driver?

Efficiency bandwidth product places the motor before anything else is decided.

EBP = Fs ÷ Qes = 54.8
SEALED 0–50 TRANSITION 50–100 PORTED 100–150 0 50 100 150 Dual 2 Ohm 54.8
Dual 2 Ohm · EBP 54.8
At 54.8 the DMD122SH DVC 2ohm sits in the transition band, not the sealed band. That is not a mismatch: a transition motor works in either alignment, and sealed buys a smaller box and a gentler roll-off at the cost of some low-end output. Stage 02 shows what this airspace actually does with it.

02What the box does to it

1.974 cu ft against a 30.7 L Vas.

α = Vas ÷ Vb = 0.55  ·  Fc = Fs√(α+1) = 57 Hz  ·  Qtc = 0.96
20 30 50 70 100 150 200 +6 +0 -6 -12 -18 -24 FREQUENCY · Hz LEVEL · dB −3 dB
Dual 2 Ohm · Qtc 0.96, Fc 57 Hz, F3 45.9 Hz
The box lifts resonance from 46.0 Hz free-air to 57 Hz and half power lands at 45.9 Hz, anechoic, before any cabin gain. Figures are Diamond Audio’s published parameters; Qes and Qms reproduce the printed Qts. This cabinet holds three drivers in three separate sealed chambers of 1.974 cubic feet each, the volume plotted here.

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 7.9 mm, and in this alignment a subsonic filter barely moves it.

PXmax = 195 W per driver unfiltered  →  199 W per driver with a 25 Hz subsonic
20 30 50 70 100 150 200 0 4 8 FREQUENCY · Hz CONE TRAVEL · mm PAST LINEAR TRAVEL · Xmax 7.9 mm 195 W reaches Xmax here
Dual 2 Ohm · 195 W, no filterDual 2 Ohm · 199 W with subsonic at 25 Hz, 24 dB/octXmax 7.9 mm one-way
Every trace touches the limit and no further, because each is drawn at the exact power that puts that coil on 7.9 mm. Unfiltered that is 195 W per driver, reached first at 39 Hz. It sits under the 300 W the driver can take thermally, so the enclosure sets the ceiling, not the voice coil. The dashed traces are the same driver behind a subsonic filter at 25 Hz, 24 dB/oct, and they sit almost on top of the solid ones: 199 W per driver against 195 W. At 57 Hz the filter sits well below resonance, where the sealed alignment has already rolled the cone off at 12 dB/oct, so there is little wasted travel left for it to recover. Set it anyway to keep road rumble out of the cone, but do not size the amplifier around it.
ParamValueUnitNote
Fs46.00Hzfree-air resonance
Qts0.770Dual 2 Ohm
Vas30.70Lequivalent compliance
Sd539.0cm²effective piston area
Xmax7.9mmone-way linear travel
Pe300Wcontinuous RMS
SPL87.4dB1 W / 1 m, derived from T/S

Driver parameters as published by Diamond Audio DMD122SH DVC 2ohm published specifications. Curves computed against this enclosure’s actual net airspace.

From the shop floor

Installer's take

Start with the size. 1.974 cubic feet per driver puts the DMD-SH at Qtc 0.958, resonance 57.3 Hz, half power 45.9 Hz anechoic. The wide platform stops at 23 inches deep, so this box lands a little above flat: a small lift near resonance and firm midbass.

Measure the base depth, not the top. This cabinet is 23.00 in deep where it meets the floor, 16.81 at the top, 44 wide and 17 tall. In an SUV the 44 has to clear between the rear wheel wells at floor height, the base depth is measured from the seat back with the seat upright and latched, and the 17 has to clear the cargo cover.

All three terminal cups are on the rear panel, and the rear panel is the face that goes against the seat back. Wire all three before the box goes in, with enough slack to slide it into place; once the raked face is against the seat you cannot reach them.

Impedance. DMD122SH DVC 2ohm: wire for 3 ohms (coils in parallel, the three in series), the load most monoblocks are built to deliver full power into; 1.33 ohms is the other clean option (coils in series, the three cups in parallel). Work the load out before you buy the amplifier, not after.

Power. Size the amplifier for the set, not one driver: 130 to 190 W RMS per driver is 390 to 570 W RMS across all 3 at 3 ohms. On this driver travel sets the top, not heat: Xmax arrives at 199 W per driver with a 25 Hz subsonic, under the 300 W rating.

Diamond Audio's Qes and Qms reproduce the printed Qts within 3 percent, so the alignment rests on a self-consistent set. Diamond Audio do not publish driver displacement; we deduct an estimated 0.048 per driver, so true net can sit a few hundredths either way.

Polyfill is in as a wall lining in every chamber. Do not add more: it makes the box act larger and walks Qtc off 0.96.

Before you order

Questions

Does this fit the Diamond Audio DMD-SH, and its coil versions?

Yes. Each opening is cut to 11.060 in for the 12.83 in frame, and the 3.00 in deep motor clears the raked rear panel with 13.51 in to spare. Coil versions of the Diamond Audio DMD-SH share the frame, cutout and mounting depth, so any of them drops in. The alignment on this page is computed on the DMD122SH DVC 2ohm parameters.

Run three matched drivers, same model and same coil, so every chamber sees the alignment on this page.

Why 1.974 cubic feet per driver, and what alignment does it target?

On Diamond Audio's published Fs 46.0 Hz, Qts 0.770 and Vas 30.7 liters, 1.974 cubic feet per driver gives Qtc 0.958, system resonance 57.3 Hz and half power 45.9 Hz.

The wide platform stops at 23 inches deep, so this box lands a little above flat: a small lift near resonance and firm midbass.

What amplifier power should I run, and how should I wire it?

Diamond Audio rates the DMD-SH at 300 watts RMS per driver. Recommended amplifier: 130 to 190 W RMS per driver, 390 to 570 W RMS for the full set of 3. Travel, not heat, sets the top: the cone reaches Xmax at 199 W per driver with a 25 Hz subsonic set, under the 300 W rating.

Each DMD122SH DVC 2ohm has two 2 ohm voice coils, 4 ohms in series or 1 ohm in parallel. With each driver's coils in series and the three cups in parallel, the three present 1.33 ohms to a mono amplifier. With each driver's coils in parallel and the three in series, they present 3 ohms. Three drivers do not reach the round loads a pair does, so check the result against your amplifier's minimum stable impedance before powering up.

Will it fit my SUV?

It is 44 inches wide, 17 tall and 23.00 deep at the base, tapering to 16.81 at the top. Measure between the rear wheel wells, the floor depth with the seat upright, and the height under your cargo cover.

The raked face goes against the seat back and the woofers fire toward the liftgate.

Why are all three terminal cups on the back?

Each driver has its own sealed chamber, and the center chamber has no side wall to take a cup. Putting all three on the rear panel gives a matching set, one cup per chamber.

Wire them at the amplifier end; there is no cross-chamber wiring inside the cabinet.

What is the expected low-frequency extension?

Anechoic F3 is 45.9 Hz per driver with system resonance at 57.3 Hz.

Those figures exclude cabin gain. An SUV cabin adds real output below about 50 Hz, so in-vehicle response runs deeper than the numbers above.

Do I need to add polyfill or damping?

No. Polyfill is already installed as a light wall lining in every chamber, and the quantity is chosen so it does not change the acoustic volume.

Do not add more. Packing a sealed box makes it behave as though it were larger, which moves the alignment away from 1.974 cubic feet per driver.

Are the drivers included?

No. This is an enclosure only. You receive the cabinet finished in plush black carpet with the gloss black acrylic baffle insert, three pre-wired terminal cups on the rear panel, the polyfill lining in place, threaded inserts and stainless machine screws.

Bring three matched Diamond Audio DMD-SH drivers. The cabinet is cut direct fit to them, not a general purpose 12 inch box.

Same series, same size

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