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Performance Optimized · Datasheet

Helix IQ W8 Dual Box: Sealed 8" Wedge Enclosure Dual 8" Sealed enclosure

Net volume
0.26 to 0.88 cu ft per driver, by setting
Tuning
No Added Mass, +1 Mass Ring, +2 Mass Rings. Each is a different cabinet, cut to order
Max mounting depth
4.51 in required by the driver
Cutout
7.2100 in, same at every setting
External dimensions
22.05 to 32.00 in across the settings W × 11 in at the seat face H × 10.76 to 16.62 in at the base D
Front baffle
1.5 in, double baffle
Buy at Audio IntensityFactory-direct, ships from Tullahoma
  • Best For: Dual Helix IQ W8 Trunk-Fit Builds
  • Net Volume: 0.26 to 0.88 cu ft per driver by Tuning Mass setting
  • Alignment: Qtc 0.659 to 0.695, fc 38.2 to 62.9 Hz, F3 38.9 to 67.9 Hz anechoic
  • Tuning Mass: 3 settings offered, cut and built to order
  • Driver Match: Pair of Helix IQ W8 (matched), DVC2
  • Impedance: 2 ohms with each driver in series, pair in parallel
  • Construction: Dual Chamber | Rear-Firing Wedge | V-Groove/Dado | Double 1.5" Baffle | Threaded Inserts

Spec of record

Technical specifications

SpecificationValue
SeriesProline X Performance Optimized Wedge
Compatible DriverHelix IQ W8 DVC2, quantity 2. Direct fit
ConfigurationDual 8 inch, dual chamber sealed wedge
Tuning Mass Settings OfferedNo Added Mass, +1 Mass Ring, +2 Mass Rings. Each is a different cabinet, cut to order
BuildCut and built to order. Nothing is pre-cut
Mounting PositionTrunk or cargo area, tall face against the rear seat back
Firing DirectionRearward into the trunk. Not a down fire design, no feet included
External Width22.05 to 32.00 in across the settings
External Height11 in at the seat face
External Depth10.76 to 16.62 in at the base, 6.76 to 12.61 in at the top
Internal Volume, Gross0.31 to 0.94 cu ft per chamber, by setting
Internal Volume, Net Acoustic0.26 to 0.88 cu ft per driver, by setting
AlignmentQtc 0.659 to 0.695, fc 38.2 to 62.9 Hz, F3 38.9 to 67.9 Hz anechoic, by setting
Helix Recommended Volume6 to 25 litres net across the settings offered
Driver Cutout7.2100 in, same at every setting
Driver Mounting Depth4.51 in required by the driver
Power Handling1500 watts RMS total across the pair
ImpedanceDVC2, dual 2 ohm: 1 ohm parallel or 4 ohm series per driver
Xmax12 mm one way
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
Weight28.2 to 49.6 lb depending on setting
Warranty1 Year Limited
Built InTullahoma, Tennessee

Modelled response

Performance in this enclosure

Net airspace
0.26–0.88
cu ft per chamber
System Qtc
0.66–0.69
sealed
Half power
38.9–67.9
Hz · F3
Xmax at
165
W RMS · no filter
With 25 Hz subsonic
264
W RMS · +60%
Amplifier
750
W RMS recommended
This enclosure holds 0.26–0.88 cu ft net per chamber. In it the Helix IQ W8 runs a system Qtc of 0.66–0.69 with half power at 38.9–67.9 Hz, and the cone reaches its 12.0 mm travel limit at 165 W, below the driver’s 750 W thermal rating, so travel is what stops you here, not heat. Run a subsonic filter at 25 Hz and that becomes 264 W — +98 W, or 60 percent more power for the same 12.0 mm of travel.

01Is it a sealed driver?

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

EBP = Fs ÷ Qes = 48.5–87.8
SEALED 0–50 TRANSITION 50–100 PORTED 100–150 0 50 100 150 0 TM 87.8 +1 TM 66.1 +2 TM 48.5
0 TM · EBP 87.8+1 TM · EBP 66.1+2 TM · EBP 48.5
The IQ W8 straddles the boundary at 48.5–87.8 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

0.26–0.88 cu ft against an 8.5 L Vas.

α = Vas ÷ Vb = 0.34–1.14  ·  Fc = Fs√(α+1) = 38–63 Hz  ·  Qtc = 0.66–0.69
20 30 50 70 100 150 200 +6 +0 -6 -12 -18 -24 FREQUENCY · Hz LEVEL · dB −3 dB
0 TM · Qtc 0.66, Fc 63 Hz, F3 67.9 Hz+1 TM · Qtc 0.69, Fc 50 Hz, F3 51.3 Hz+2 TM · Qtc 0.69, Fc 38 Hz, F3 38.9 Hz
The box lifts resonance from 33.0–43.0 Hz free-air to 38–63 Hz and half power lands at 38.9–67.9 Hz, anechoic, before any cabin gain. Every Tuning Mass setting this listing offers is plotted here, each in ITS OWN cabinet: 0 TM at 0.26 cu ft, +1 TM at 0.35 cu ft, +2 TM at 0.88 cu ft. That is the comparison, four different boxes for four different cone masses, not one box with the weights swapped. Helix supplies the weights with the driver and publishes a different recommended volume for each, because mass changes resonance and total Q while compliance, and therefore Vas, does not move. Power figures are per driver, for one driver in its own chamber. Note that 0 TM is NOT at Helix's volume: there they ask for 6 litres and the smallest cabinet this chassis can build holds more, so the curve is drawn at the volume we actually cut. The F3 figures are anechoic. Unlike the IK series, Helix's own printed figures for the IQ reconcile with them, because these datasheets carry no recommended DSP highpass.

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

PXmax = 165–377 W unfiltered  →  264–461 W with a 25 Hz subsonic
20 30 50 70 100 150 200 0 4 8 12 FREQUENCY · Hz CONE TRAVEL · mm PAST LINEAR TRAVEL · Xmax 12.0 mm 165 W reaches Xmax here
0 TM · 377 W, no filter+1 TM · 276 W, no filter+2 TM · 165 W, no filter0 TM · 461 W with subsonic at 25 Hz, 24 dB/oct+1 TM · 359 W with subsonic at 25 Hz, 24 dB/oct+2 TM · 264 W with subsonic at 25 Hz, 24 dB/octXmax 12.0 mm one-way
Every trace touches the limit and no further, because each is drawn at the exact power that puts that coil on 12.0 mm. Unfiltered that is 165 W, reached first at 20 Hz. It sits under the 750 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 264 W before hitting the same 12.0 mm. That is 60 percent more amplifier for the price of one filter setting.
ParamValueUnitNote
Fs43.00 / 37.00 / 33.00Hzfree-air resonance
Qts0.450 / 0.510 / 0.6000 TM / +1 TM / +2 TM
Vas8.50 / 8.50 / 8.50Lequivalent compliance
Sd222.0cm²effective piston area
Xmax12mmone-way linear travel
Pe750Wcontinuous RMS
SPL83.2dB1 W / 1 m, derived from T/S

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

From the shop floor

Installer's take

0.26 to 0.88 cubic feet net per driver at Qtc 0.659 to 0.695 and F3 38.9 to 67.9 Hz anechoic, depending on which Tuning Mass setting you order. Every figure is computed from Helix's published Thiele-Small for that setting.

The IQ series carries Helix's Tuning Mass System: bolt-on weights that thread onto the cone assembly and let one driver run several alignments. Each weight raises moving mass, which drops free-air resonance and raises the driver's total Q, and Helix publishes a different recommended sealed volume for every setting to keep the system in hand. This cabinet is offered in no added mass, +1 mass ring and +2 mass rings, 6 to 25 litres of Helix's own recommended volume, and across those the system Q works out at 0.70 at the base setting and 0.69 at the top of the range offered. What does not change is compliance, and therefore Vas, because mass and spring rate are independent.

The IQ W8 ships with three weights. The top setting, all three fitted, is not offered as a listed size here; call or text 931-563-5151 if that is the alignment you want and we will quote the cabinet for it.

Every one of these is cut and built to order. Nothing is pre-cut and nothing sits on a shelf waiting for a Tuning Mass setting to be chosen, because each setting is a different cabinet rather than a label on one. Pick the setting you intend to run and the panels are cut to it.

On the F3 figures: Helix prints a lower limiting frequency for every Tuning Mass setting, and ours agree with theirs to within 1.7 Hz at every setting offered here. That is worth stating because it is not true of every Helix line. The IK datasheets quote their figure with a recommended DSP highpass applied and read several hertz optimistic against the raw sealed response; the IQ sheets carry no filter recommendation and their numbers reconcile with the anechoic math. Both F3 columns in the table above are anechoic and exclude cabin gain.

On impedance: The IQ series ships in one coil version, the DVC2: two 2 ohm coils per driver. Across a pair the sensible target is 2 ohms, reached by wiring each driver's coils in series for 4 ohms and then the two drivers in parallel. Both drivers must be wired identically, and any route to 1 ohm needs an amplifier rated for it.

Marked with an asterisk: at no added mass the IQ W8 wants less air than the smallest cabinet this chassis can build. The 0.26 cu ft figure listed is what we actually cut, which is 0.05 above Helix's figure, and the Qtc shown is the one that volume produces rather than the 0.70 they publish. The cost is about a hertz of F3 and a slightly drier alignment. We would rather print the number we build.

Measure before you order, and measure for the setting you actually want. These range from 22.05 to 32.00 inches wide, 10.76 to 16.62 deep at the base and 11 tall.

Before you order

Questions

What is the Tuning Mass System and which setting should I order?

The IQ series carries Helix's Tuning Mass System: bolt-on weights that thread onto the cone assembly and let one driver run several alignments. Each weight raises moving mass, which drops free-air resonance and raises the driver's total Q, and Helix publishes a different recommended sealed volume for every setting to keep the system in hand. This cabinet is offered in no added mass, +1 mass ring and +2 mass rings, 6 to 25 litres of Helix's own recommended volume, and across those the system Q works out at 0.70 at the base setting and 0.69 at the top of the range offered. What does not change is compliance, and therefore Vas, because mass and spring rate are independent. Fewer weights give a smaller cabinet, a higher resonance and a drier, faster presentation; more weights give a bigger cabinet and deeper extension. Order the setting you intend to run, because the cabinet is cut to it. The IQ W8 ships with three weights. The top setting, all three fitted, is not offered as a listed size here; call or text 931-563-5151 if that is the alignment you want and we will quote the cabinet for it. Every one of these is cut and built to order. Nothing is pre-cut and nothing sits on a shelf waiting for a Tuning Mass setting to be chosen, because each setting is a different cabinet rather than a label on one. Pick the setting you intend to run and the panels are cut to it.

Why does each setting get a different volume?

Because Helix publishes a different recommended sealed volume for each one, and the reason is physics rather than preference. Adding mass drops the driver's free air resonance and raises its total Q, so holding system Q near reference means growing the box. Compliance does not change, so Vas stays at 8.5 litres throughout. The table on this page lists what we build for each setting.

What amplifier power should I run, and what impedance?

The Helix IQ W8 is rated 750 watts RMS each, so 1500 across the pair, and that does not change with the Tuning Mass setting. The IQ series ships in one coil version, the DVC2: two 2 ohm coils per driver. Across a pair the sensible target is 2 ohms, reached by wiring each driver's coils in series for 4 ohms and then the two drivers in parallel. Both drivers must be wired identically, and any route to 1 ohm needs an amplifier rated for it. Aim for roughly 1050 to 1500 watts at whichever impedance you wire to.

Does your F3 agree with the figure on Helix's datasheet?

Helix prints a lower limiting frequency for every Tuning Mass setting, and ours agree with theirs to within 1.7 Hz at every setting offered here. That is worth stating because it is not true of every Helix line. The IK datasheets quote their figure with a recommended DSP highpass applied and read several hertz optimistic against the raw sealed response; the IQ sheets carry no filter recommendation and their numbers reconcile with the anechoic math. Both F3 columns in the table above are anechoic and exclude cabin gain.

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 between 38.9 and 67.9 Hz depending on the setting anechoic, before any cabin gain, with Qtc from 0.659 to 0.695. 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 for the cabinet you ordered, so it does not change the acoustic volume. Do not add more.

Is the driver included, and how long does it take to build?

No. This is an enclosure only, and the Tuning Mass weights come with the driver from Helix rather than with the cabinet. You receive the box finished in plush black carpet, with threaded inserts at both driver positions, stainless machine screws, one side-mounted pre-wired terminal cup and the polyfill lining already installed. Because every setting is a different cabinet, nothing is cut ahead of time and these are built to order. Call or text 931-563-5151 for current lead time.

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