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Proline X PO 8D-S DF IKS8 sealed down fire enclosure, front panel on 1.75 inch feet, 30 by 5.9 inches.
Proline X PO 8D-S DF IKS8 sealed down fire enclosure, end panel with recessed terminal cup, 15 by 5.9 inches.

Performance Optimized · Datasheet

Helix IK S8 Dual Box: Sealed 8" Shallow Down Fire Enclosure Dual 8" Sealed enclosure

Net volume
0.71 cu ft total, 0.35 per driver
Max mounting depth
3.13 in required by the driver
Cutout
7.1000 in
External dimensions
30.00 in W × 5.92 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 S8Buy at Audio Intensity
  • Best For: Dual Helix IK S8 Floor-Firing Builds
  • Net Volume: 0.35 cu ft per driver (0.39 cu ft Gross per chamber)
  • Alignment: Qtc 0.725 to 0.739, fc 62.3 Hz, F3 59.7 to 60.8 Hz anechoic
  • Driver Match: Pair of Helix IK S8 (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

SpecificationValue
SeriesProline X Performance Optimized Down Fire
Compatible DriverHelix IK S8 SVC2 or DVC2, quantity 2. Direct fit
ConfigurationDual 8 inch, dual chamber sealed down fire
Mounting PositionTrunk or cargo floor, cone firing downward
Firing DirectionDownward into the floor. Feet included, uninstalled
External Width30.00 in
External Height5.92 in measured in the down fire position
External Depth15 in
Internal Volume, Gross0.79 cu ft total, 0.39 per chamber
Internal Volume, Net Acoustic0.71 cu ft total, 0.35 per driver
AlignmentQtc 0.725 to 0.739, fc 62.3 Hz, F3 59.7 to 60.8 Hz anechoic
Helix Recommended Volume10 litres net, which is what this is built to
Driver Cutout7.1000 in
Driver Mounting Depth3.13 in required by the driver
Power Handling600 watts RMS total across the pair
Floor Slot Ratio1.13 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 BracingFull chamber divider
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
Weight32.7 lb
Warranty1 Year Limited
Built InTullahoma, Tennessee

Modelled response

Performance in this enclosure

Net airspace
0.35
cu ft per chamber
System Qtc
0.72–0.74
sealed
Half power
59.7–60.8
Hz · F3
Xmax at
73
W RMS · no filter
With 25 Hz subsonic
83
W RMS · +14%
Amplifier
300
W RMS recommended
This enclosure holds 0.35 cu ft net per chamber. In it the Helix IK S8 runs a system Qtc of 0.72–0.74 with half power at 59.7–60.8 Hz, and the cone reaches its 6.0 mm travel limit at 73 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 83 W — +10 W, or 14 percent more power for the same 6.0 mm of travel.

01Is it a sealed driver?

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

EBP = Fs ÷ Qes = 75.4–81.1
SEALED 0–50 TRANSITION 50–100 PORTED 100–150 0 50 100 150 SVC2 81.1 DVC2 75.4
SVC2 · EBP 81.1DVC2 · EBP 75.4
At 75.4–81.1 the IK S8 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 an 11.0 L Vas.

α = Vas ÷ Vb = 1.10  ·  Fc = Fs√(α+1) = 62 Hz  ·  Qtc = 0.72–0.74
20 30 50 70 100 150 200 +6 +0 -6 -12 -18 -24 FREQUENCY · Hz LEVEL · dB −3 dB
SVC2 · Qtc 0.72, Fc 62 Hz, F3 60.8 HzDVC2 · Qtc 0.74, Fc 62 Hz, F3 59.7 Hz
The box lifts resonance from 43.0 Hz free-air to 62 Hz and half power lands at 59.7–60.8 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 6.0 mm — and a bigger one once a subsonic filter stops it wasting travel below the passband.

PXmax = 73–78 W unfiltered  →  83–87 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 6.0 mm 73 W reaches Xmax here
SVC2 · 73 W, no filterDVC2 · 78 W, no filterSVC2 · 83 W with subsonic at 25 Hz, 24 dB/octDVC2 · 87 W with subsonic at 25 Hz, 24 dB/octXmax 6.0 mm one-way
Every trace touches the limit and no further, because each is drawn at the exact power that puts that coil on 6.0 mm. Unfiltered that is 73 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 83 W before hitting the same 6.0 mm. That is 14 percent more amplifier for the price of one filter setting.
ParamValueUnitNote
Fs43.00Hzfree-air resonance
Qts0.500 / 0.510SVC2 / DVC2
Vas11.00 / 11.00Lequivalent compliance
Sd222.0cm²effective piston area
Xmax6mmone-way linear travel
Pe300Wcontinuous RMS
SPL84.0dB1 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 per driver at Qtc 0.725 to 0.739 and F3 59.7 to 60.8 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, 10 litres. That is what this cabinet is cut to, giving Qtc 0.725 with the SVC2 and 0.739 with the DVC2.

Do not be thrown by the F3. Half power lands at 59.7 to 60.8 Hz anechoic, before any cabin gain. Helix's own datasheet prints 46 Hz for this driver, which is a different measurement rather than a disagreement: their figure is quoted with their recommended 46 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 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 5.92 tall in the down fire position.

Before you order

Questions

Will this fit the IK S8 SVC2 and the DVC2?

Yes. The two coil versions share a frame, a 7.1000 in cutout and the same 3.13 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, 10 litres. That is what this cabinet is cut to, giving Qtc 0.725 with the SVC2 and 0.739 with the DVC2.

Why 0.35 cubic feet net per driver?

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 0.39 cu ft gross before the driver's displacement.

What amplifier power should I run, and what impedance?

The Helix IK S8 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 59.7 to 60.8 Hz anechoic, before any cabin gain. Helix's own datasheet prints 46 Hz for this driver, which is a different measurement rather than a disagreement: their figure is quoted with their recommended 46 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 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 59.7 to 60.8 Hz anechoic, before any cabin gain. Qtc is 0.725 to 0.739. 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.

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