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Proline X PO 8-S DF IKW8 sealed down fire enclosure, front panel on 1.75 inch feet, 18.2 by 5.5 inches.
Proline X PO 8-S DF IKW8 sealed down fire enclosure, end panel with recessed terminal cup, 15 by 5.5 inches.

Performance Optimized · Datasheet

Helix IK W8 Box: Sealed 8" Down Fire Enclosure Single 8" Sealed enclosure

Net volume
0.35 cu ft
Max mounting depth
3.98 in required by the driver
Cutout
7.1700 in
External dimensions
18.19 in W × 5.48 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 W8Buy at Audio Intensity
  • Best For: Helix IK W8 Floor-Firing Builds
  • Net Volume: 0.35 cu ft (0.40 cu ft Gross)
  • Alignment: Qtc 0.673 to 0.674, fc 56.6 to 60.8 Hz, F3 59.6 to 64.0 Hz anechoic
  • Driver Match: Helix IK W8, SVC2 or DVC2
  • Impedance: 2 ohm SVC2; 1 or 4 ohm DVC2
  • Construction: Down-Firing Sealed | V-Groove/Dado | Double 1.5" Baffle | Threaded Inserts | Feet Included

Spec of record

Technical specifications

SpecificationValue
SeriesProline X Performance Optimized Down Fire
Compatible DriverHelix IK W8 SVC2 or DVC2, quantity 1. Direct fit
ConfigurationSingle 8 inch, single chamber sealed down fire
Mounting PositionTrunk or cargo floor, cone firing downward
Firing DirectionDownward into the floor. Feet included, uninstalled
External Width18.19 in
External Height5.48 in measured in the down fire position
External Depth15 in
Internal Volume, Gross0.40 cu ft
Internal Volume, Net Acoustic0.35 cu ft
AlignmentQtc 0.673 to 0.674, fc 56.6 to 60.8 Hz, F3 59.6 to 64.0 Hz anechoic
Helix Recommended Volume10 litres net, which is what this is built to
Driver Cutout7.1700 in
Driver Mounting Depth3.98 in required by the driver
Power Handling300 watts RMS
Floor Slot Ratio1.16 at the standard 1.75 in standoff
FeetIncluded, uninstalled
ImpedanceSVC2 is a single 2 ohm coil; DVC2 is dual 2 ohm, 1 ohm parallel or 4 ohm series
Xmax8 mm one way, both coil versions
MaterialLangboard Elite MDF
ConstructionCNC cut, V-groove and dado joinery
Panel Thickness0.75 in
Front Baffle1.5 in, double baffle
Internal BracingInternal brace
Driver MountingThreaded inserts at every mounting location, stainless machine screws included
Terminal CupsOne Proline X ABS and carbon fiber composite, side mounted, pre wired 12 gauge OFC
DampingLight polyfill wall lining, does not alter acoustic volume
CarpetPlush black
Weight19.8 lb
Warranty1 Year Limited
Built InTullahoma, Tennessee

Modelled response

Performance in this enclosure

Net airspace
0.35
cu ft per chamber
System Qtc
0.67
sealed
Half power
59.6–64.0
Hz · F3
Xmax at
104
W RMS · no filter
With 25 Hz subsonic
126
W RMS · +22%
Amplifier
300
W RMS recommended
This enclosure holds 0.35 cu ft net per chamber. In it the Helix IK W8 runs a system Qtc of 0.67 with half power at 59.6–64.0 Hz, and the cone reaches its 8.0 mm travel limit at 104 W, below the driver’s 300 W thermal rating, so travel is what stops you here, not heat. Run a subsonic filter at 25 Hz and that becomes 126 W — +22 W, or 22 percent more power for the same 8.0 mm of travel.

01Is it a sealed driver?

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

EBP = Fs ÷ Qes = 75.5–80.4
SEALED 0–50 TRANSITION 50–100 PORTED 100–150 0 50 100 150 SVC2 75.5 DVC2 80.4
SVC2 · EBP 75.5DVC2 · EBP 80.4
At 75.5–80.4 the IK W8 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

0.35 cu ft against a 13.4 L Vas.

α = Vas ÷ Vb = 1.34  ·  Fc = Fs√(α+1) = 57–61 Hz  ·  Qtc = 0.67
20 30 50 70 100 150 200 +6 +0 -6 -12 -18 -24 FREQUENCY · Hz LEVEL · dB −3 dB
SVC2 · Qtc 0.67, Fc 57 Hz, F3 59.6 HzDVC2 · Qtc 0.67, Fc 61 Hz, F3 64.0 Hz
The box lifts resonance from 37.0 Hz free-air to 57–61 Hz and half power lands at 59.6–64.0 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 a bigger one once a subsonic filter stops it wasting travel below the passband.

PXmax = 104–106 W unfiltered  →  126–133 W with a 25 Hz subsonic
20 30 50 70 100 150 200 0 4 8 FREQUENCY · Hz CONE TRAVEL · mm PAST LINEAR TRAVEL · Xmax 8.0 mm 104 W reaches Xmax here
SVC2 · 106 W, no filterDVC2 · 104 W, no filterSVC2 · 133 W with subsonic at 25 Hz, 24 dB/octDVC2 · 126 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 104 W, reached first at 20 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: stopping the cone wasting travel below the passband lets it take 126 W before hitting the same 8.0 mm. That is 22 percent more amplifier for the price of one filter setting.
ParamValueUnitNote
Fs37.00Hzfree-air resonance
Qts0.440 / 0.410SVC2 / DVC2
Vas13.40 / 17.00Lequivalent compliance
Sd219.0cm²effective piston area
Xmax8mmone-way linear travel
Pe300Wcontinuous RMS
SPL83.3dB1 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

0.35 cubic feet net at Qtc 0.673 to 0.674 and F3 59.6 to 64.0 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, and on this model they recommend different volumes: 10 litres for the SVC2 and 8 for the DVC2. This cabinet is cut to the larger, which puts both versions on almost the same alignment: Qtc 0.673 with the SVC2 and 0.674 with the DVC2.

Do not be thrown by the F3. Half power lands at 59.6 to 64.0 Hz anechoic, before any cabin gain. Helix's own datasheet prints 50 Hz for this driver, which is a different measurement rather than a disagreement: their figure is quoted with their recommended 50 Hz, Q 1.5 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 they wire differently. The SVC2 is a single 2 ohm coil, so one driver presents 2 ohms and there is nothing to decide. The DVC2 carries two 2 ohm coils: in parallel that is 1 ohm, in series 4 ohms. Pick the one your amplifier is rated for, and note that 1 ohm needs an amplifier that says so.

This cabinet is 18.19 inches wide rather than the 30 inches a Proline X down fire normally runs. That is deliberate. A 30 inch footprint holds more air than the IK W8 wants, and a sealed driver in too much air loses damping rather than gaining depth, so the cabinet is cut narrower to land on Helix's volume exactly.

Measure before you order. This cabinet is 18.19 inches wide by 15 deep and 5.48 tall in the down fire position.

Before you order

Questions

Will this fit the IK W8 SVC2 and the DVC2?

Yes. The two coil versions share a frame, a 7.1700 in cutout and the same 3.98 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, and on this model they recommend different volumes: 10 litres for the SVC2 and 8 for the DVC2. This cabinet is cut to the larger, which puts both versions on almost the same alignment: Qtc 0.673 with the SVC2 and 0.674 with the DVC2.

Why 0.35 cubic feet net?

Because that is the sealed volume Helix publishes for this driver, 10 litres, and it is a net figure in their documentation exactly as it is in ours. Each chamber is 0.40 cu ft gross before the driver's displacement.

What amplifier power should I run, and what impedance?

The Helix IK W8 is rated 300 watts RMS each, so 300. The IK W series comes in two coil versions and they wire differently. The SVC2 is a single 2 ohm coil, so one driver presents 2 ohms and there is nothing to decide. The DVC2 carries two 2 ohm coils: in parallel that is 1 ohm, in series 4 ohms. Pick the one your amplifier is rated for, and note that 1 ohm needs an amplifier that says so. Aim for roughly 210 to 300 watts at whichever impedance you wire to.

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

Half power lands at 59.6 to 64.0 Hz anechoic, before any cabin gain. Helix's own datasheet prints 50 Hz for this driver, which is a different measurement rather than a disagreement: their figure is quoted with their recommended 50 Hz, Q 1.5 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 is this narrower than your other down fire cabinets?

This cabinet is 18.19 inches wide rather than the 30 inches a Proline X down fire normally runs. That is deliberate. A 30 inch footprint holds more air than the IK W8 wants, and a sealed driver in too much air loses damping rather than gaining depth, so the cabinet is cut narrower to land on Helix's volume exactly.

What is the expected low-frequency extension?

Half power lands at 59.6 to 64.0 Hz anechoic, before any cabin gain. Qtc is 0.673 to 0.674. 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.

Is the driver included?

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

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