Proline X PO 12D-S DF IKW12 sealed down fire enclosure, front panel on 1.75 inch feet, 30 by 10.5 inches.

Proline X PO 12D-S DF IKW12 sealed down fire enclosure, end panel with recessed terminal cup, 15 by 10.5 inches.

Performance Optimized · Datasheet

Helix IK W12 Dual Box: Sealed 12" Down Fire Enclosure Dual 12" Sealed enclosure

Net volume: 1.55 cu ft total, 0.78 per driver
Max mounting depth: 5.67 in required by the driver
Cutout: 11.2600 in
External dimensions: 30.00 in W × 10.45 in measured in the down fire position H × 15 in D
Front baffle: 1.5 in, double baffle

Buy at Audio IntensityFactory-direct, ships from Tullahoma

Helix IK W12Buy at Audio Intensity

Best For: Dual Helix IK W12 Floor-Firing Builds
Net Volume: 0.78 cu ft per driver (0.88 cu ft Gross per chamber)
Alignment: Qtc 0.820 to 0.868, fc 57.2 to 64.0 Hz, F3 48.5 to 56.4 Hz anechoic
Driver Match: Pair of Helix IK W12 (matched), SVC2 or DVC2
Impedance: 1 or 4 ohm with SVC2; 2 ohm with DVC2
Construction: Dual Chamber | Down-Firing Sealed | V-Groove/Dado | Double 1.5" Baffle | Threaded Inserts | Feet Included

Spec of record

Technical specifications

Specification	Value
Series	Proline X Performance Optimized Down Fire
Compatible Driver	Helix IK W12 SVC2 or DVC2, quantity 2. Direct fit
Configuration	Dual 12 inch, dual chamber sealed down fire
Mounting Position	Trunk or cargo floor, cone firing downward
Firing Direction	Downward into the floor. Feet included, uninstalled
External Width	30.00 in
External Height	10.45 in measured in the down fire position
External Depth	15 in
Internal Volume, Gross	1.76 cu ft total, 0.88 per chamber
Internal Volume, Net Acoustic	1.55 cu ft total, 0.78 per driver
Alignment	Qtc 0.820 to 0.868, fc 57.2 to 64.0 Hz, F3 48.5 to 56.4 Hz anechoic
Helix Recommended Volume	22 litres net, which is what this is built to
Driver Cutout	11.2600 in
Driver Mounting Depth	5.67 in required by the driver
Power Handling	600 watts RMS total across the pair
Floor Slot Ratio	0.78 at the standard 1.75 in standoff
Feet	Included, uninstalled
Impedance	SVC2 is a single 2 ohm coil; DVC2 is dual 2 ohm, 1 ohm parallel or 4 ohm series
Xmax	8 mm one way, both coil versions
Material	Langboard Elite MDF
Construction	CNC cut, V-groove and dado joinery
Panel Thickness	0.75 in
Front Baffle	1.5 in, double baffle
Internal Bracing	Full chamber divider
Driver Mounting	Threaded inserts at every mounting location, stainless machine screws included
Terminal Cups	One Proline X ABS and carbon fiber composite, side mounted, pre wired 12 gauge OFC
Damping	Light polyfill wall lining, does not alter acoustic volume
Carpet	Plush black
Weight	37 lb
Warranty	1 Year Limited
Built In	Tullahoma, Tennessee

Modelled response

Performance in this enclosure

Net airspace

0.78

cu ft per chamber

System Qtc

0.82–0.87

sealed

Half power

48.5–56.4

Hz · F3

Xmax at

248

W RMS · no filter

With 25 Hz subsonic

260

W RMS · +5%

Amplifier

300

W RMS recommended

This enclosure holds 0.78 cu ft net per chamber. In it the Helix IK W12 runs a system Qtc of 0.82–0.87 with half power at 48.5–56.4 Hz, and the cone reaches its 8.0 mm travel limit at 248 W, 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: 260 W against 248 W, 5 percent. The box already resonates at 57–64 Hz, so its own rolloff has removed most of what the filter would have stopped.

01Is it a sealed driver?

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

EBP = Fs ÷ Qes = 57.4–69.6

SVC2 · EBP 57.4DVC2 · EBP 69.6

At 57.4–69.6 the IK W12 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

0.78 cu ft against a 53.0 L Vas.

α = Vas ÷ Vb = 2.41 · Fc = Fs√(α+1) = 57–64 Hz · Qtc = 0.82–0.87

SVC2 · Qtc 0.87, Fc 57 Hz, F3 48.5 HzDVC2 · Qtc 0.82, Fc 64 Hz, F3 56.4 Hz

The box lifts resonance from 31.0–32.0 Hz free-air to 57–64 Hz and half power lands at 48.5–56.4 Hz, anechoic, before any cabin gain. The wedge and the down-fire, single and dual, all hold this same volume per chamber, so these numbers describe every version of this enclosure. Power figures are per driver, for one driver in its own chamber. Helix measures the SVC2 and the DVC2 separately rather than publishing one set for both, so both are carried here rather than averaged. Note that the F3 above is anechoic and reads higher than the figure on Helix's datasheet, which is quoted with their recommended DSP highpass applied.

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

P_Xmax = 248–254 W unfiltered → 260–265 W with a 25 Hz subsonic

SVC2 · 248 W, no filterDVC2 · 254 W, no filterSVC2 · 260 W with subsonic at 25 Hz, 24 dB/octDVC2 · 265 W with subsonic at 25 Hz, 24 dB/octXmax 8.0 mm one-way

Every trace touches the limit and no further, because each is drawn at the exact power that puts that coil on 8.0 mm. Unfiltered that is 248 W, reached first at 33 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: 260 W against 248 W. At 57–64 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.

Param	Value	Unit	Note
Fs	31.00 / 32.00	Hz	free-air resonance
Qts	0.470 / 0.410		SVC2 / DVC2
Vas	53.00 / 66.00	L	equivalent compliance
Sd	515.0	cm²	effective piston area
Xmax	8	mm	one-way linear travel
Pe	300	W	continuous RMS
SPL	86.5	dB	1 W / 1 m, derived from T/S

Driver parameters as published by audiotec-fischer.de and the HELIX datasheet. Curves computed against this enclosure’s actual net airspace.

From the shop floor

Installer's take

0.78 cubic feet net per driver at Qtc 0.820 to 0.868 and F3 48.5 to 56.4 Hz anechoic, computed from Helix's published Thiele-Small. That is Helix's own recommended sealed volume.

Helix measures the SVC2 and the DVC2 separately rather than publishing one set of parameters for both, but on this model they land on the same recommended volume, 22 litres. That is what this cabinet is cut to, giving Qtc 0.868 with the SVC2 and 0.820 with the DVC2.

Do not be thrown by the F3. Half power lands at 48.5 to 56.4 Hz anechoic, before any cabin gain. Helix's own datasheet prints 40 Hz for this driver, which is a different measurement rather than a disagreement: their figure is quoted with their recommended 37 Hz, Q 1.6 highpass applied, and a filter at that corner lifts the response enough to move the half-power point down to meet it. The number above is the raw sealed response of this cabinet.

On impedance: The IK W series comes in two coil versions and a pair wires differently in each. Two SVC2 drivers, each a single 2 ohm coil, give 1 ohm in parallel or 4 ohms in series. Two DVC2 drivers give more choices; the sensible target is 2 ohms, reached by wiring each driver's coils in series for 4 ohms and then the pair in parallel. Every driver in the cabinet must be wired identically, and 1 ohm needs an amplifier rated for it.

Measure before you order. This cabinet is 30.00 inches wide by 15 deep and 10.45 tall in the down fire position.

Before you order

Questions

Will this fit the IK W12 SVC2 and the DVC2?

Yes. The two coil versions share a frame, a 11.2600 in cutout and the same 5.67 in mounting depth, so the cabinet fits either. Helix measures the SVC2 and the DVC2 separately rather than publishing one set of parameters for both, but on this model they land on the same recommended volume, 22 litres. That is what this cabinet is cut to, giving Qtc 0.868 with the SVC2 and 0.820 with the DVC2.

Why 0.78 cubic feet net per driver?

Because that is the sealed volume Helix publishes for this driver, 22 litres, and it is a net figure in their documentation exactly as it is in ours. Each chamber is 0.88 cu ft gross before the driver's displacement.

What amplifier power should I run, and what impedance?

The Helix IK W12 is rated 300 watts RMS each, so 600 across the pair. The IK W series comes in two coil versions and a pair wires differently in each. Two SVC2 drivers, each a single 2 ohm coil, give 1 ohm in parallel or 4 ohms in series. Two DVC2 drivers give more choices; the sensible target is 2 ohms, reached by wiring each driver's coils in series for 4 ohms and then the pair in parallel. Every driver in the cabinet must be wired identically, and 1 ohm needs an amplifier rated for it. Aim for roughly 420 to 600 watts at whichever impedance you wire to.

Why is your F3 higher than the one on Helix's datasheet?

Half power lands at 48.5 to 56.4 Hz anechoic, before any cabin gain. Helix's own datasheet prints 40 Hz for this driver, which is a different measurement rather than a disagreement: their figure is quoted with their recommended 37 Hz, Q 1.6 highpass applied, and a filter at that corner lifts the response enough to move the half-power point down to meet it. The number above is the raw sealed response of this cabinet.

Why two separate chambers instead of one shared one?

A shared chamber lets each cone modulate the other's air load, which makes the pair less predictable under hard excursion. A full divider gives each driver its own sealed volume, so both behave exactly as the single version does.

What is the expected low-frequency extension?

Half power lands at 48.5 to 56.4 Hz anechoic, before any cabin gain. Qtc is 0.820 to 0.868. These figures exclude cabin gain, which in most vehicles adds real output below 40 Hz, and they exclude any DSP you choose to run.

Do I need to add polyfill or damping?

No. Polyfill is already installed as a light wall lining and the quantity is chosen so it does not change the acoustic volume. Do not add more.

Are the drivers included?

No. This is an enclosure only. You receive the cabinet finished in plush black carpet, with threaded inserts at both driver positions, stainless machine screws, one side-mounted pre-wired terminal cup, the feet uninstalled and the polyfill lining already installed.

Same series, same size