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Proline X PO 12T-S W HZ12 sealed wedge enclosure, product photos pending. Placeholder graphic reading Photos Coming Soon.

Performance Optimized · Datasheet

Performance Optimized Wedge Wide Sealed Triple 12" Enclosure Sundown Audio Horizon HZ 12 · Triple 12" Sealed enclosure

Net volume
1.000 cu ft per driver, 3.00 cu ft total, after both dividers and Sundown Audio's published 0.120 cu ft displacement per driver
Max mounting depth
6.30 in required; 2.67 in clearance above the motor against the raked rear panel
External dimensions
44 in W × 17 in at the seat face H × 15.46 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
Sundown Audio Horizon HZ 12Buy at Audio Intensity
  • Best For: Triple Sundown Audio Horizon HZ 12 SUV Cargo-Floor Builds
  • Net Volume: 1.000 cu ft per Driver (3.00 cu ft Net Total)
  • Driver Match: Three Sundown Audio Horizon HZ 12 (D4), 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 DriverSundown Audio Horizon HZ 12, 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 Depth15.46 in at the base, tapering to 9.27 in at the top
Internal Volume, Gross3.49 cu ft total
Internal Volume, Net Acoustic1.000 cu ft per driver, 3.00 cu ft total, after both dividers and Sundown Audio's published 0.120 cu ft displacement per driver
Driver Mounting Depth6.30 in required; 2.67 in clearance above the motor against the raked rear panel
Alignment Per DriverHorizon HZ 12 D4 Qtc 0.882, fc 54.2 Hz, F3 45.5 Hz anechoic
Woofer Openings3 at 11.200 in
Woofer LayoutOne row across the face
Frame Outer Diameter12.5 in
Fs / Qts / Qes / Qms31.7 Hz / 0.516 / 0.598 / 3.770
Vas / Sd / Xmax54.4 L / 505 cm2 / 14 mm
Driver Power Handling500 W RMS per driver, 1500 W RMS for the set of 3 (thermal rating)
Recommended Amplifier350-500 W RMS per driver, 1,050-1,500 W RMS for the full set, at 2.67 ohms
Parameter SourceSundown 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 Weight76 lb
Warranty1 Year Limited
Built InTullahoma, Tennessee

Modelled response

Performance in this enclosure

Net airspace
1.000
cu ft per driver
System Qtc
0.88
sealed
Half power
45.5
Hz · F3
Xmax at
583
W RMS per driver · no filter
With 25 Hz subsonic
616
W RMS per driver · +6%
Amplifier, per driver
350–500
W RMS recommended
This enclosure holds 1.000 cu ft net per driver. In it the Sundown Audio Horizon HZ 12 D4 runs a system Qtc of 0.88 with half power at 45.5 Hz, and the cone reaches its 14.0 mm travel limit at 583 W per driver, above the driver’s 500 W thermal rating, so heat stops you before travel does. Run a subsonic filter at 25 Hz and that becomes 616 W per driver — +33 W, or 6 percent more power for the same 14.0 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 350–500 W RMS  ×  3 drivers  =  full set 1,050–1,500 W RMS at 2.67 ohms
Look for a mono amplifier rated 1,050–1,500 W RMS at 2.67 ohms, the load the set wires to most easily. The top is the driver’s 500 W thermal rating; with the 25 Hz subsonic set the cone still has travel to spare there, reaching Xmax only at 616 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 = 53.0
SEALED 0–50 TRANSITION 50–100 PORTED 100–150 0 50 100 150 D4 53.0
D4 · EBP 53.0
At 53.0 the Horizon HZ 12 D4 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

1.000 cu ft against a 54.4 L Vas.

α = Vas ÷ Vb = 1.92  ·  Fc = Fs√(α+1) = 54 Hz  ·  Qtc = 0.88
20 30 50 70 100 150 200 +6 +0 -6 -12 -18 -24 FREQUENCY · Hz LEVEL · dB −3 dB
D4 · Qtc 0.88, Fc 54 Hz, F3 45.5 Hz
The box lifts resonance from 31.7 Hz free-air to 54 Hz and half power lands at 45.5 Hz, anechoic, before any cabin gain. Figures are Sundown Audio’s published parameters; Qes and Qms reproduce the printed Qts. This cabinet holds three drivers in three separate sealed chambers of 1.000 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 14.0 mm — and a bigger one once a subsonic filter stops it wasting travel below the passband.

PXmax = 583 W per driver unfiltered  →  616 W per driver with a 25 Hz subsonic
20 30 50 70 100 150 200 0 4 8 12 16 FREQUENCY · Hz CONE TRAVEL · mm PAST LINEAR TRAVEL · Xmax 14.0 mm 583 W reaches Xmax here
D4 · 583 W, no filterD4 · 616 W with subsonic at 25 Hz, 24 dB/octXmax 14.0 mm one-way
Every trace touches the limit and no further, because each is drawn at the exact power that puts that coil on 14.0 mm. Unfiltered that is 583 W per driver, reached first at 32 Hz. It sits above the 500 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 616 W per driver before hitting the same 14.0 mm. That is 6 percent more amplifier for the price of one filter setting.
ParamValueUnitNote
Fs31.70Hzfree-air resonance
Qts0.516D4
Vas54.36Lequivalent compliance
Sd505.2cm²effective piston area
Xmax14mmone-way linear travel
Pe500Wcontinuous RMS
SPL86.5dB1 W / 1 m, derived from T/S

Driver parameters as published by Sundown Audio Horizon HZ 12 D4 published specifications. Curves computed against this enclosure’s actual net airspace.

From the shop floor

Installer's take

Start with the size. 1.000 cubic feet per driver puts the Horizon HZ 12 at Qtc 0.882, resonance 54.2 Hz, half power 45.5 Hz anechoic. That is Sundown Audio's number, not ours: the cabinet is built to the maker's recommended sealed size. Butterworth on these figures wants 2.19, which on this platform means deeper than the 23 in platform allows. It is a small lift near resonance, 0.6 dB above flat.

Measure the base depth, not the top. This cabinet is 15.46 in deep where it meets the floor, 9.27 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. Horizon HZ 12 D4: wire for 2.67 ohms (coils in series, the three cups in parallel), the load most monoblocks are built to deliver full power into; 6 ohms is the other clean option (coils in parallel, the three in series). Work the load out before you buy the amplifier, not after.

Power. Size the amplifier for the set, not one driver: 350 to 500 W RMS per driver is 1,050 to 1,500 W RMS across all 3 at 2.67 ohms.

Sundown Audio's Qes and Qms reproduce the printed Qts within 3 percent, so the alignment rests on a self-consistent set.

Polyfill is in as a wall lining in every chamber. Do not add more: it makes the box act larger and walks Qtc off 0.88.

Before you order

Questions

Does this fit the Sundown Audio Horizon HZ 12, and its coil versions?

Yes. Each opening is cut to 11.200 in for the 12.5 in frame, and the 6.30 in deep motor clears the raked rear panel with 2.67 in to spare. Coil versions of the Sundown Audio Horizon HZ 12 share the frame, cutout and mounting depth, so any of them drops in. The alignment on this page is computed on the Horizon HZ 12 D4 parameters.

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

Why 1.000 cubic feet per driver, and what alignment does it target?

On Sundown Audio's published Fs 31.7 Hz, Qts 0.516 and Vas 54.4 liters, 1.000 cubic feet per driver gives Qtc 0.882, system resonance 54.2 Hz and half power 45.5 Hz.

The cabinet is sized to the maker's recommended sealed size, 1.00 cubic feet per driver, to keep it realistic for a cargo floor. Maximally flat would need 2.19 cubic feet per driver; this size trades a little low end for a compact box and a small lift near resonance, 0.6 dB above flat.

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

Sundown Audio rates the Horizon HZ 12 at 500 watts RMS per driver. Recommended amplifier: 350 to 500 W RMS per driver, 1,050 to 1,500 W RMS for the full set of 3.

Each Horizon HZ 12 D4 has two 4 ohm voice coils, 8 ohms in series or 2 ohms in parallel. With each driver's coils in series and the three cups in parallel, the three present 2.67 ohms to a mono amplifier. With each driver's coils in parallel and the three in series, they present 6 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 15.46 deep at the base, tapering to 9.27 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 45.5 Hz per driver with system resonance at 54.2 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 1.000 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 Sundown Audio Horizon HZ 12 drivers. The cabinet is cut direct fit to them, not a general purpose 12 inch box.

Same series, same size

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