Alpine Proline PO 12-S W R2 woofers shown in a black acrylic enclosure with a circular opening, labeled as 18 by 15 inches, on a dark blue background with product specifications and branding.Proline X PO 12-S W R2 sealed wedge enclosure, side profile with recessed terminal cup, 6.8 inch top, 13.1 inch base, 15 inches tall. Optimized for Alpine R2-W.

Performance Optimized · Datasheet

Performance Optimized Wedge Sealed 12" Enclosure | Alpine R2-W12 Single 12" Sealed enclosure

Net volume
0.75 Cubic Feet
Max mounting depth
7.45 Inches (Alpine Spec)
Cutout
10.79 Inches (Alpine Spec)
External dimensions
18 Inches W × 15 Inches H × 6.85 Inches / 13.125 Inches D
Front baffle
Vertical Trunk-Lid-Side Woofer Mounting Face
Buy at Audio Intensity
  • Best For: Alpine R2-W12 Trunk-Fit Daily Driver Builds
  • Net Volume: 0.75 cu ft (0.85 cu ft Gross)
  • Driver Match: Alpine R2-W12 (D2 or D4)
  • Construction: Rear-Firing Wedge | V-Groove/Dado | Double 1.5" Baffle | Threaded Inserts

Technical specifications

Enclosure TypeSealed | Wedge Geometry | Rear-Firing Trunk-Load
Driver-Specific FitmentAlpine R2-W12 - R2-W12D2 (DVC 2Ω) or R2-W12D4 (DVC 4Ω)
Internal Volume (Gross)0.85 Cubic Feet
Internal Volume (Net After Displacement)0.75 Cubic Feet
Target System Qtc (D2)0.68 (Near-Butterworth Musical | Based on Published T/S)
Target System Qtc (D4)0.81 (Punchy | Based on Published T/S)
Predicted F3~43-50 Hz (Depending on Coil)
Predicted Fc~48 Hz
Driver Displacement0.10 Cubic Feet (Published by Alpine)
Baffle ConfigurationVertical Trunk-Lid-Side Woofer Mounting Face
MaterialLangboard Elite 3/4" MDF
Front Baffle ConstructionDouble-Layer 1.5" MDF (Two 3/4" Sheets Bonded)
JoineryV-Groove and Dado (CNC-Cut)
ConstructionShopSabre CNC / Angled Seat-Side Compound Cuts / Perimeter Cross-Brace
External Width18 Inches
External Height15 Inches
External Depth (Top)6.85 Inches
External Depth (Bottom)13.125 Inches
Baffle Angle~23° From Vertical (Seat-Side Face)
Mounting Hole Diameter10.79 Inches (Alpine Spec)
Mounting Depth Required7.45 Inches (Alpine Spec)
Mounting Hardware8/32 Threaded Inserts | Stainless Steel Machine Screws Included
Terminal CupProline X ABS/Carbon Fiber Composite | 12g OFC Pre-Wired
DampingPolyfill Pre-Installed
Recommended Power500-750 Watts RMS (Alpine Rated: 750W RMS Continuous)
Carpet FinishDark Gray Trunkliner (Standard) or Plush Black
Acrylic InsertBlack, Blue, Red, White, or None
Bundle OptionsEnclosure Only (Bring Your Own R2-W12D2 or R2-W12D4)
Warranty1-Year Limited (Enclosure)
ManufacturedTullahoma, Tennessee, USA

Performance in this enclosure

Net airspace
0.75
cu ft per chamber
System Qtc
0.68–0.81
sealed
Half power
42.4–50.1
Hz · F3
Xmax at
1132
W RMS · no filter
With 25 Hz subsonic
1467
W RMS · +30%
Amplifier
750
W RMS recommended
This enclosure holds 0.75 cu ft net per chamber. In it the Alpine R2-W12D2 runs a system Qtc of 0.68–0.81 with half power at 42.4–50.1 Hz, and the cone reaches its 20.0 mm travel limit at 1132 W, above the driver’s 750 W thermal rating, so heat stops you before travel does. Run a subsonic filter at 25 Hz and that becomes 1467 W — +335 W, or 30 percent more power for the same 20.0 mm of travel.

01Is it a sealed driver?

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

EBP = Fs ÷ Qes = 54.5–65.9
SEALED 0–50 TRANSITION 50–100 PORTED 100–150 0 50 100 150 D2 65.9 D4 54.5
D2 · EBP 65.9D4 · EBP 54.5
At 54.5–65.9 the R2-W12D2 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

0.75 cu ft against a 36.9 L Vas.

α = Vas ÷ Vb = 1.74  ·  Fc = Fs√(α+1) = 48–48 Hz  ·  Qtc = 0.68–0.81
20 30 50 70 100 150 200 +6 +0 -6 -12 -18 -24 FREQUENCY · Hz LEVEL · dB −3 dB
D2 · Qtc 0.68, Fc 48 Hz, F3 50.1 HzD4 · Qtc 0.81, Fc 48 Hz, F3 42.4 Hz
The box lifts resonance from 29.0 Hz free-air to 48–48 Hz and half power lands at 42.4–50.1 Hz, anechoic, before any cabin gain. This enclosure ships without a driver, so both coil variants the maker offers are plotted. They do not load the same box the same way.

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 20.0 mm — and a bigger one once a subsonic filter stops it wasting travel below the passband.

PXmax = 1132–1261 W unfiltered  →  1467–1545 W 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 20.0 mm 1132 W reaches Xmax here
D2 · 1132 W, no filterD4 · 1261 W, no filterD2 · 1545 W with subsonic at 25 Hz, 24 dB/octD4 · 1467 W with subsonic at 25 Hz, 24 dB/octXmax 20.0 mm one-way
Every trace touches the limit and no further, because each is drawn at the exact power that puts that coil on 20.0 mm. Unfiltered that is 1132 W, reached first at 20 Hz. It sits above the 750 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 1467 W before hitting the same 20.0 mm. That is 30 percent more amplifier for the price of one filter setting.
ParamValueUnitNote
Fs29.00Hzfree-air resonance
Qts0.410 / 0.510D2 / D4
Vas36.90 / 32.80Lequivalent compliance
Sd479.0cm²effective piston area
Xmax20mmone-way linear travel
Pe750Wcontinuous RMS
SPL85.0dB1 W / 1 m, derived from T/S

Driver parameters as published by Alpine R2-W Thiele-Small sheet CN_TS_R2-W (2022). Curves computed against this enclosure’s actual net airspace.

Installer's take

The Alpine R2-W12 is the flagship of the R2 12-inch platform. 750 watts RMS, 20mm one-way Xmax, 72mm mechanical travel, 144 oz double-stacked strontium ferrite motor, 65.5mm 4-layer voice coil on aluminum former. Everything Alpine builds into their top-tier woofers, dropped into their most popular size.

This cabinet lands at 0.75 cubic feet net, which sits right at Alpine's own recommended sealed volume. The D2 coil produces Qtc 0.68 - a near-Butterworth musical alignment. The D4 coil produces Qtc 0.81 - punchier, tighter, and with slightly less low-end extension. Neither is textbook 0.707 but both are usable, well-controlled alignments. If you strongly favor the D2 target, this is the right cabinet. If you're on the D4 coil and want a tighter alignment, this still works well; if you want a looser D4 alignment, a larger cabinet (~1.25 cu ft net) would get you closer to Butterworth on that coil.

The double-baffle 1.5" front is not optional on this driver. The R2-W12 exerts serious mechanical load into the mounting flange at high output, and a single 3/4" layer will telegraph flex back into the cone. Two bonded 3/4" layers with the CNC-precision cutout stops that entirely.

If you're bringing your own amp, target 500-750 watts RMS at the woofer's final wired impedance. The R2-W12's 8AWG push terminals with VC configuration jumpers let you wire the dual voice coils in series or parallel right at the driver.

Questions

Will this enclosure fit both the R2-W12D2 and R2-W12D4?

Yes. Direct-fit for either impedance option. The two coils have T/S parameters that produce meaningfully different Qtc values - D2 lands near Butterworth (0.68), D4 lands punchier (0.81). Both are usable.

Why did you pick 0.75 cubic feet net?

0.75 cubic feet net matches Alpine's own recommended sealed volume for the R2-W12 and lands D2 at Qtc 0.68 (near-Butterworth musical), D4 at Qtc 0.81 (punchier). Alpine publishes these exact Qtc values at this volume.

What amplifier power should I run to this enclosure?

Alpine R2-W12 is rated 750W RMS continuous. Target 500-750W RMS at the woofer's final wired impedance.

How does a wedge enclosure improve the sound in a trunk installation?

The wedge geometry angles the driver rear-firing into the trunk at approximately 23 degrees from vertical.

Why is the front baffle double-layered on this enclosure?

Double-layer 1.5 inch front baffle from bonded 3/4 inch Langboard Elite MDF. Eliminates flex under high mechanical load given the R2-W12's 20mm Xmax and 750W rating.

What is the expected low-frequency extension of this enclosure?

Predicted -3 dB is approximately 43 Hz with D2 (Qtc 0.68) and approximately 50 Hz with D4 (Qtc 0.81). Cabin gain extends effective in-car response into the upper 20 Hz range.

Do I need to add any additional damping or polyfill to this enclosure?

No additional damping required. Polyfill is pre-installed to the correct density for the volume and alignment.

Is the Alpine R2-W12 subwoofer included with this enclosure?

No. Enclosure only. Bring your own R2-W12D2 (DVC 2Ω) or R2-W12D4 (DVC 4Ω) driver.

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