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Proline X PO 12T-S W UMII12 sealed wedge enclosure, product photos pending. Placeholder graphic reading Photos Coming Soon.

Performance Optimized · Datasheet

Dayton Audio Ultimax II UMII12 Triple Box: Sealed 12" Wedge Wide Enclosure Triple 12" Sealed enclosure

Net volume
1.905 cu ft per driver, 5.71 cu ft total, after both dividers and an estimated 0.117 cu ft displacement per driver
Max mounting depth
7.06 in required; 9.45 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
Dayton Audio Ultimax II UMII12Buy at Audio Intensity
  • Best For: Triple Dayton Audio Ultimax II UMII12 SUV Cargo-Floor Builds
  • Net Volume: 1.905 cu ft per Driver (5.71 cu ft Net Total)
  • Driver Match: Three Dayton Audio Ultimax II UMII12 (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 DriverDayton Audio Ultimax II UMII12, 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 Acoustic1.905 cu ft per driver, 5.71 cu ft total, after both dividers and an estimated 0.117 cu ft displacement per driver
Driver Mounting Depth7.06 in required; 9.45 in clearance above the motor against the raked rear panel
Alignment Per DriverUMII12-22 Qtc 0.788, fc 43.6 Hz, F3 39.6 Hz anechoic
Woofer Openings3 at 11.272 in
Woofer LayoutOne row across the face
Frame Outer Diameter12.654 in
Fs / Qts / Qes / Qms31.0 Hz / 0.560 / 0.710 / 2.750
Vas / Sd / Xmax53.0 L / 528 cm2 / 22 mm
Driver Power Handling800 W RMS per driver, 2400 W RMS for the set of 3 (thermal rating)
Recommended Amplifier560-800 W RMS per driver, 1,680-2,400 W RMS for the full set, at 3 ohms
Parameter SourceDayton 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
1.905
cu ft per driver
System Qtc
0.79
sealed
Half power
39.6
Hz · F3
Xmax at
951
W RMS per driver · no filter
With 25 Hz subsonic
1209
W RMS per driver · +27%
Amplifier, per driver
560–800
W RMS recommended
This enclosure holds 1.905 cu ft net per driver. In it the Dayton Audio UMII12-22 runs a system Qtc of 0.79 with half power at 39.6 Hz, and the cone reaches its 22.0 mm travel limit at 951 W per driver, above the driver’s 800 W thermal rating, so heat stops you before travel does. Run a subsonic filter at 25 Hz and that becomes 1209 W per driver — +258 W, or 27 percent more power for the same 22.0 mm of travel.

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 560–800 W RMS  ×  3 drivers  =  full set 1,680–2,400 W RMS at 3 ohms
Look for a mono amplifier rated 1,680–2,400 W RMS at 3 ohms, the load the set wires to most easily. The top is the driver’s 800 W thermal rating; with the 25 Hz subsonic set the cone still has travel to spare there, reaching Xmax only at 1209 W. 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 = 43.7
SEALED 0–50 TRANSITION 50–100 PORTED 100–150 0 50 100 150 Dual 2 Ohm 43.7
Dual 2 Ohm · EBP 43.7
EBP under 50 means a motor that wants a sealed load. The UMII12-22 sits at 43.7, inside that band, which is why this is a sealed build rather than a ported one.

02What the box does to it

1.905 cu ft against a 53.0 L Vas.

α = Vas ÷ Vb = 0.98  ·  Fc = Fs√(α+1) = 44 Hz  ·  Qtc = 0.79
20 30 50 70 100 150 200 +6 +0 -6 -12 -18 -24 FREQUENCY · Hz LEVEL · dB −3 dB
Dual 2 Ohm · Qtc 0.79, Fc 44 Hz, F3 39.6 Hz
The box lifts resonance from 31.0 Hz free-air to 44 Hz and half power lands at 39.6 Hz, anechoic, before any cabin gain. Figures are Dayton Audio’s published parameters; Qes and Qms reproduce the printed Qts. This cabinet holds three drivers in three separate sealed chambers of 1.905 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 22.0 mm — and a bigger one once a subsonic filter stops it wasting travel below the passband.

PXmax = 951 W per driver unfiltered  →  1209 W per driver with a 25 Hz subsonic
20 30 50 70 100 150 200 0 8 16 24 FREQUENCY · Hz CONE TRAVEL · mm PAST LINEAR TRAVEL · Xmax 22.0 mm 951 W reaches Xmax here
Dual 2 Ohm · 951 W, no filterDual 2 Ohm · 1209 W with subsonic at 25 Hz, 24 dB/octXmax 22.0 mm one-way
Every trace touches the limit and no further, because each is drawn at the exact power that puts that coil on 22.0 mm. Unfiltered that is 951 W per driver, reached first at 20 Hz. It sits above the 800 W the driver can take thermally, so the voice coil gives up before the suspension does. The dashed traces are the same driver behind a subsonic filter at 25 Hz, 24 dB/oct: stopping the cone wasting travel below the passband lets it take 1209 W per driver before hitting the same 22.0 mm. That is 27 percent more amplifier for the price of one filter setting.
ParamValueUnitNote
Fs31.00Hzfree-air resonance
Qts0.560Dual 2 Ohm
Vas53.00Lequivalent compliance
Sd528.0cm²effective piston area
Xmax22mmone-way linear travel
Pe800Wcontinuous RMS
SPL85.3dB1 W / 1 m, derived from T/S

Driver parameters as published by Dayton Audio UMII12-22 published specifications. Curves computed against this enclosure’s actual net airspace.

From the shop floor

Installer's take

Start with the size. 1.905 cubic feet per driver puts the Ultimax II UMII12 at Qtc 0.788, resonance 43.6 Hz, half power 39.6 Hz anechoic. Maximally flat on these figures would need 3.15 cubic feet per driver. 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. UMII12-22: 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: 560 to 800 W RMS per driver is 1,680 to 2,400 W RMS across all 3 at 3 ohms. At 2,400 W the charging system is part of the install: alternator output, the big three, and a battery that holds voltage under load.

Dayton Audio's Qes and Qms reproduce the printed Qts within 3 percent, so the alignment rests on a self-consistent set. Dayton Audio do not publish driver displacement; we deduct an estimated 0.117 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 0.79.

Before you order

Questions

Does this fit the Dayton Audio Ultimax II UMII12, and its coil versions?

Yes. Each opening is cut to 11.272 in for the 12.654 in frame, and the 7.06 in deep motor clears the raked rear panel with 9.45 in to spare. Coil versions of the Dayton Audio Ultimax II UMII12 share the frame, cutout and mounting depth, so any of them drops in. The alignment on this page is computed on the UMII12-22 parameters.

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

Why 1.905 cubic feet per driver, and what alignment does it target?

On Dayton Audio's published Fs 31.0 Hz, Qts 0.560 and Vas 53.0 liters, 1.905 cubic feet per driver gives Qtc 0.788, system resonance 43.6 Hz and half power 39.6 Hz.

Maximally flat on these figures would need 3.15 cubic feet per driver. 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?

Dayton Audio rates the Ultimax II UMII12 at 800 watts RMS per driver. Recommended amplifier: 560 to 800 W RMS per driver, 1,680 to 2,400 W RMS for the full set of 3.

Each UMII12-22 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 39.6 Hz per driver with system resonance at 43.6 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 1.905 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 Dayton Audio Ultimax II UMII12 drivers. The cabinet is cut direct fit to them, not a general purpose 12 inch box.

Same series, same size

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