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

Performance Optimized · Datasheet

Performance Optimized Wedge Wide Sealed Triple 12" Enclosure Hertz Mille Pro MPS 300 · Triple 12" Sealed enclosure

Net volume: 1.714 cu ft per driver, 5.14 cu ft total, after both dividers and an estimated 0.057 cu ft displacement per driver
Max mounting depth: 3.46 in required; 10.94 in clearance above the motor against the raked rear panel
External dimensions: 44 in W × 17 in at the seat face H × 20.90 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

Hertz Mille Pro MPS 300Buy at Audio Intensity

Best For: Triple Hertz Mille Pro MPS 300 SUV Cargo-Floor Builds
Net Volume: 1.714 cu ft per Driver (5.14 cu ft Net Total)
Driver Match: Three Hertz Mille Pro MPS 300 (Single 2 Ohm / Single 4 Ohm), matched
Construction: 3 Chambers | 44" Wide Wedge | V-Groove/Dado | Double 1.5" Baffle | 3 Terminal Cups

Spec of record

Technical specifications

Specification	Value
Series	Proline X Performance Optimized Wedge Wide
Compatible Driver	Hertz Mille Pro MPS 300, quantity 3, matched. Direct fit
Configuration	Triple 12 inch sealed wedge, 3 chambers, 1 driver per chamber
Mounting Position	SUV cargo floor, raked face against the rear seat back
Firing Direction	Rearward toward the liftgate. Not a down fire design
External Width	44 in
External Height	17 in at the seat face
External Depth	20.90 in at the base, tapering to 14.71 in at the top
Internal Volume, Gross	5.51 cu ft total
Internal Volume, Net Acoustic	1.714 cu ft per driver, 5.14 cu ft total, after both dividers and an estimated 0.057 cu ft displacement per driver
Driver Mounting Depth	3.46 in required; 10.94 in clearance above the motor against the raked rear panel
Alignment Per Driver	MPS 300 12" S2 Qtc 0.780, fc 36.7 Hz, F3 33.6 Hz; MPS 300 12" S4 Qtc 0.634, fc 34.7 Hz, F3 39.2 Hz anechoic
Woofer Openings	3 at 11.122 in
Woofer Layout	One row across the face
Frame Outer Diameter	12.531 in
Fs / Qts / Qes / Qms	24.0 Hz / 0.510 / 0.550 / 7.500
Vas / Sd / Xmax	64.9 L / 534 cm2 / 17 mm
Driver Power Handling	500 W RMS per driver, 1500 W RMS for the set of 3 (thermal rating)
Recommended Amplifier	350-500 W RMS per driver, 1,050-1,500 W RMS for the full set
Parameter Source	Hertz published specifications
Material	Langboard Elite MDF
Construction	CNC cut, V-groove and dado joinery
Panel Thickness	0.75 in
Front Baffle	1.5 in double baffle, outer layer machined as a flush recess
Internal Bracing	Two full-height 3/4 in dividers
Driver Mounting	Threaded inserts, stainless machine screws included
Terminal Cups	Three Proline X ABS and carbon fiber composite, on the rear panel, one per chamber, pre wired 12 gauge OFC
Acrylic Insert	Gloss black acrylic baffle insert standard
Damping	Light polyfill wall lining in every chamber, does not alter acoustic volume
Carpet	Plush black
Shipping Weight	93 lb
Warranty	1 Year Limited
Built In	Tullahoma, Tennessee

Modelled response

Performance in this enclosure

Net airspace

1.714

cu ft per driver

System Qtc

0.63–0.78

sealed

Half power

33.6–39.2

Hz · F3

Xmax at

395

W RMS per driver · no filter

With 25 Hz subsonic

596

W RMS per driver · +51%

Amplifier, per driver

350–500

W RMS recommended

This enclosure holds 1.714 cu ft net per driver. In it the Hertz MPS 300 12" S2 runs a system Qtc of 0.63–0.78 with half power at 33.6–39.2 Hz, and the cone reaches its 16.8 mm travel limit at 395 W per driver, below the driver’s 500 W thermal rating, so travel is what stops you here, not heat. Run a subsonic filter at 25 Hz and that becomes 596 W per driver — +200 W, or 51 percent more power for the same 16.8 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

Look for a mono amplifier rated 1,050–1,500 W RMS at the load your coil version wires to. 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 596 W. The top of the range needs the 25 Hz subsonic filter set; without it, keep each driver under 395 W, where the cone reaches Xmax unfiltered. 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 = 43.6–51.1

Single 2 Ohm · EBP 43.6Single 4 Ohm · EBP 51.1

The MPS 300 12" S2 straddles the boundary at 43.6–51.1 depending on coil — part sealed-band, part transition. Either way it takes a sealed load happily; the coil you run shifts the alignment more than it shifts this verdict.

02What the box does to it

1.714 cu ft against a 64.9 L Vas.

α = Vas ÷ Vb = 1.34 · Fc = Fs√(α+1) = 35–37 Hz · Qtc = 0.63–0.78

Single 2 Ohm · Qtc 0.78, Fc 37 Hz, F3 33.6 HzSingle 4 Ohm · Qtc 0.63, Fc 35 Hz, F3 39.2 Hz

The box lifts resonance from 23.0–24.0 Hz free-air to 35–37 Hz and half power lands at 33.6–39.2 Hz, anechoic, before any cabin gain. Figures are Hertz’s published parameters; Qes and Qms reproduce the printed Qts. This cabinet holds three drivers in three separate sealed chambers of 1.714 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 16.8 mm — and a bigger one once a subsonic filter stops it wasting travel below the passband.

P_Xmax = 395–399 W per driver unfiltered → 596–742 W with a 25 Hz subsonic

Single 2 Ohm · 395 W, no filterSingle 4 Ohm · 399 W, no filterSingle 2 Ohm · 596 W with subsonic at 25 Hz, 24 dB/octSingle 4 Ohm · 742 W with subsonic at 25 Hz, 24 dB/octXmax 16.8 mm one-way

Every trace touches the limit and no further, because each is drawn at the exact power that puts that coil on 16.8 mm. Unfiltered that is 395 W per driver, reached first at 20 Hz. It sits under the 500 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: stopping the cone wasting travel below the passband lets it take 596 W per driver before hitting the same 16.8 mm. That is 51 percent more amplifier for the price of one filter setting.

Param	Value	Unit	Note
Fs	24.00 / 23.00	Hz	free-air resonance
Qts	0.510 / 0.420		Single 2 Ohm / Single 4 Ohm
Vas	64.90 / 62.13	L	equivalent compliance
Sd	534.5	cm²	effective piston area
Xmax	16.8	mm	one-way linear travel
Pe	500	W	continuous RMS
SPL	84.0	dB	1 W / 1 m, derived from T/S

Driver parameters as published by Hertz MPS 300 12" S2 / MPS 300 12" S4 published specifications. Curves computed against this enclosure’s actual net airspace.

From the shop floor

Installer's take

Start with the size. 1.714 cubic feet per driver puts the Mille Pro MPS 300 at Qtc 0.780, resonance 36.7 Hz, half power 33.6 Hz anechoic. One box serves Single 2 Ohm and Single 4 Ohm, so the depth is the one that keeps both closest to 0.707. One box serves every coil version: the Single 2 Ohm at Qtc 0.780, the Single 4 Ohm at Qtc 0.634.

Measure the base depth, not the top. This cabinet is 20.90 in deep where it meets the floor, 14.71 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. MPS 300 12" S2: wire for 6 ohms (the three in series), the load most monoblocks are built to deliver full power into; 0.67 ohms is the other clean option (the three in parallel). MPS 300 12" S4: wire for 12 ohms (the three in series), the load most monoblocks are built to deliver full power into; 1.33 ohms is the other clean option (the three in parallel). 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. Set the 25 Hz subsonic to use the top of that range; without it keep each driver under 395 W.

Hertz's Qes and Qms reproduce the printed Qts within 3 percent, so the alignment rests on a self-consistent set. Hertz do not publish driver displacement; we deduct an estimated 0.057 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 0.78.

Before you order

Questions

Does this fit the Hertz Mille Pro MPS 300, and its coil versions?

Yes. Each opening is cut to 11.122 in for the 12.531 in frame, and the 3.46 in deep motor clears the raked rear panel with 10.94 in to spare. Both coil versions share the frame, cutout and mounting depth; the alignment table lists each.

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

Why 1.714 cubic feet per driver, and what alignment does it target?

On Hertz's published Fs 24.0 Hz, Qts 0.510 and Vas 64.9 liters, 1.714 cubic feet per driver gives Qtc 0.780, system resonance 36.7 Hz and half power 33.6 Hz.

One box serves Single 2 Ohm and Single 4 Ohm, so the depth is the one that keeps both closest to 0.707.

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

Hertz rates the Mille Pro MPS 300 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. The top of that range needs the 25 Hz subsonic; without it keep each driver under 395 W.

Each MPS 300 12" S2 has a single 2 ohm voice coil. The three in parallel present 0.67 ohms; in series, 6 ohms. Check the result against your amplifier's minimum stable impedance before powering up. Each MPS 300 12" S4 has a single 4 ohm voice coil. The three in parallel present 1.33 ohms; in series, 12 ohms. 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 20.90 deep at the base, tapering to 14.71 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 33.6 Hz per driver with system resonance at 36.7 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 1.714 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 Hertz Mille Pro MPS 300 drivers. The cabinet is cut direct fit to them, not a general purpose 12 inch box.

Same series, same size