Proline X PO 8T-S W SPK8 sealed wedge enclosure, product photos pending. Placeholder graphic reading Photos Coming Soon.

Performance Optimized · Datasheet

AudioControl Spike SPK-8 Triple Box: Sealed 8" Wedge Enclosure Triple 8" Sealed enclosure

Net volume: 0.500 cu ft per driver, 1.50 cu ft total, after both dividers and AudioControl's published 0.050 cu ft displacement per driver
Max mounting depth: 4.29 in required; 5.93 in clearance above the motor against the raked rear panel
External dimensions: 32 in W × 11 in at the seat face H × 15.72 in at the base D
Front baffle: 1.5 in double baffle, outer layer machined as a flush recess

Buy at Audio IntensityFactory-direct, ships from Tullahoma

AudioControl Spike SPK-8Buy at Audio Intensity

Best For: Triple AudioControl Spike SPK-8 Trunk-Fit Builds
Net Volume: 0.500 cu ft per Driver (1.50 cu ft Net Total)
Driver Match: Three AudioControl Spike SPK-8 (Single 4 Ohm), matched
Construction: 3 Chambers | 32" Rear-Firing Wedge | V-Groove/Dado | Double 1.5" Baffle | 3 Terminal Cups

Spec of record

Technical specifications

Specification	Value
Series	Proline X Performance Optimized Wedge
Compatible Driver	AudioControl Spike SPK-8, quantity 3, matched. Direct fit
Configuration	Triple 8 inch sealed wedge, 3 chambers, 1 driver per chamber
Mounting Position	Trunk floor, raked face against the rear seat back
Firing Direction	Rearward into the trunk. Not a down fire design
External Width	32 in
External Height	11 in at the seat face
External Depth	15.72 in at the base, tapering to 11.72 in at the top
Internal Volume, Gross	1.74 cu ft total
Internal Volume, Net Acoustic	0.500 cu ft per driver, 1.50 cu ft total, after both dividers and AudioControl's published 0.050 cu ft displacement per driver
Driver Mounting Depth	4.29 in required; 5.93 in clearance above the motor against the raked rear panel
Alignment Per Driver	SPK-8S4 Qtc 0.852, fc 68.2 Hz, F3 58.6 Hz anechoic
Woofer Openings	3 at 7.250 in
Woofer Layout	One row across the face
Frame Outer Diameter	8.425 in
Fs / Qts / Qes / Qms	60.4 Hz / 0.753 / 0.873 / 5.493
Vas / Sd / Xmax	3.9 L / 194 cm2 / 8 mm
Driver Power Handling	350 W RMS per driver, 1050 W RMS for the set of 3 (thermal rating)
Recommended Amplifier	170-240 W RMS per driver, 510-720 W RMS for the full set, at 12 ohms
Parameter Source	AudioControl published specifications
Material	Langboard Elite MDF
Construction	CNC cut, V-groove and dado joinery
Panel Thickness	0.75 in
Front Baffle	1.5 in double baffle, outer layer machined as a flush recess
Internal Bracing	Two full-height 3/4 in dividers
Driver Mounting	Threaded insert kit and stainless machine screws included; no bolt circle is published
Terminal Cups	Three Proline X ABS and carbon fiber composite, on the rear panel, one per chamber, pre wired 12 gauge OFC
Acrylic Insert	Gloss black acrylic baffle insert standard
Damping	Light polyfill wall lining in every chamber, does not alter acoustic volume
Carpet	Plush black
Shipping Weight	48 lb
Warranty	1 Year Limited
Built In	Tullahoma, Tennessee

Modelled response

Performance in this enclosure

Net airspace

0.500

cu ft per driver

System Qtc

0.85

sealed

Half power

58.6

Hz · F3

Xmax at

241

W RMS per driver · no filter

With 25 Hz subsonic

246

W RMS per driver · +2%

Amplifier, per driver

170–240

W RMS recommended

This enclosure holds 0.500 cu ft net per driver. In it the AudioControl SPK-8S4 runs a system Qtc of 0.85 with half power at 58.6 Hz, and the cone reaches its 8.5 mm travel limit at 241 W per driver, below the driver’s 350 W thermal rating, so travel is what stops you here, not heat. A 25 Hz subsonic filter adds little here: 246 W per driver against 241 W, 2 percent. The box already resonates at 68 Hz, so its own rolloff has removed most of what the filter would have stopped.

00Sizing the amplifier

Every wattage on this panel is per driver. This cabinet holds three, so the amplifier feeds all three at once.

Per driver 170–240 W RMS × 3 drivers = full set 510–720 W RMS at 12 ohms

Look for a mono amplifier rated 510–720 W RMS at 12 ohms, the load the set wires to most easily. Travel sets the top here, not heat: past 246 W per driver the cone runs beyond Xmax even with the subsonic set, under the driver’s 350 W thermal rating. Below the bottom of the range it will play, just with less headroom; above the top you are buying power the drivers cannot use.

01Is it a sealed driver?

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

EBP = Fs ÷ Qes = 69.1

Single 4 Ohm · EBP 69.1

At 69.1 the SPK-8S4 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

0.500 cu ft against a 3.9 L Vas.

α = Vas ÷ Vb = 0.28 · Fc = Fs√(α+1) = 68 Hz · Qtc = 0.85

Single 4 Ohm · Qtc 0.85, Fc 68 Hz, F3 58.6 Hz

The box lifts resonance from 60.4 Hz free-air to 68 Hz and half power lands at 58.6 Hz, anechoic, before any cabin gain. Figures are AudioControl’s published parameters; Qes and Qms reproduce the printed Qts. This cabinet holds three drivers in three separate sealed chambers of 0.500 cubic feet each, the volume plotted here.

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

P_Xmax = 241 W per driver unfiltered → 246 W per driver with a 25 Hz subsonic

Single 4 Ohm · 241 W, no filterSingle 4 Ohm · 246 W with subsonic at 25 Hz, 24 dB/octXmax 8.5 mm one-way

Every trace touches the limit and no further, because each is drawn at the exact power that puts that coil on 8.5 mm. Unfiltered that is 241 W per driver, reached first at 38 Hz. It sits under the 350 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: 246 W per driver against 241 W. At 68 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	60.37	Hz	free-air resonance
Qts	0.753		Single 4 Ohm
Vas	3.94	L	equivalent compliance
Sd	194.0	cm²	effective piston area
Xmax	8.5	mm	one-way linear travel
Pe	350	W	continuous RMS
SPL	81.8	dB	1 W / 1 m, derived from T/S

Driver parameters as published by AudioControl SPK-8S4 published specifications. Curves computed against this enclosure’s actual net airspace.

From the shop floor

Installer's take

Start with the size. 0.500 cubic feet per driver puts the Spike SPK-8 at Qtc 0.852, resonance 68.2 Hz, half power 58.6 Hz anechoic. That is the maker's own recommended sealed size for this driver. It is a small lift near resonance, 0.4 dB above flat.

Measure the base depth, not the top. This cabinet is 15.72 in deep where it meets the floor, 11.72 at the top, 32 wide and 11 tall. In a trunk the 32 has to clear the opening and the wheel wells, the base depth is measured from the seat back with the seat upright and latched, and the 11 has to clear the rear deck.

All three terminal cups are on the rear panel, and the rear panel is the face that goes against the seat back. Wire all three before the box goes in, with enough slack to slide it into place; once the raked face is against the seat you cannot reach them.

Impedance. SPK-8S4: wire for 12 ohms (the three in series), the load most monoblocks are built to deliver full power into; 1.33 ohms is the other clean option (the three in parallel). Work the load out before you buy the amplifier, not after.

Power. Size the amplifier for the set, not one driver: 170 to 240 W RMS per driver is 510 to 720 W RMS across all 3 at 12 ohms. On this driver travel sets the top, not heat: Xmax arrives at 246 W per driver with a 25 Hz subsonic, under the 350 W rating.

AudioControl's Qes and Qms reproduce the printed Qts within 3 percent, so the alignment rests on a self-consistent set.

Polyfill is in as a wall lining in every chamber. Do not add more: it makes the box act larger and walks Qtc off 0.85.

Before you order

Questions

Does this fit the AudioControl Spike SPK-8, and its coil versions?

Yes. Each opening is cut to 7.250 in for the 8.425 in frame, and the 4.29 in deep motor clears the raked rear panel with 5.93 in to spare. Coil versions of the AudioControl Spike SPK-8 share the frame, cutout and mounting depth, so any of them drops in. The alignment on this page is computed on the SPK-8S4 parameters.

Run three matched drivers, same model and same coil, so every chamber sees the alignment on this page.

Why 0.500 cubic feet per driver, and what alignment does it target?

On AudioControl's published Fs 60.4 Hz, Qts 0.753 and Vas 3.9 liters, 0.500 cubic feet per driver gives Qtc 0.852, system resonance 68.2 Hz and half power 58.6 Hz.

The cabinet is built to 0.50 cubic feet per driver, the maker's own recommended sealed size for the AudioControl Spike SPK-8. this size trades a little low end for a compact box and a small lift near resonance, 0.4 dB above flat.

What amplifier power should I run, and how should I wire it?

AudioControl rates the Spike SPK-8 at 350 watts RMS per driver. Recommended amplifier: 170 to 240 W RMS per driver, 510 to 720 W RMS for the full set of 3. Travel, not heat, sets the top: the cone reaches Xmax at 246 W per driver with a 25 Hz subsonic set, under the 350 W rating.

Each SPK-8S4 has a single 4 ohm voice coil. The three in parallel present 1.33 ohms; in series, 12 ohms. Check the result against your amplifier's minimum stable impedance before powering up.

Will it fit my trunk?

It is 32 inches wide, 11 tall and 15.72 deep at the base, tapering to 11.72 at the top. Measure the trunk opening, the floor depth from the seat back, and the height under the rear deck.

The raked face goes against the seat back and the woofers fire rearward into the trunk.

Why are all three terminal cups on the back?

Each driver has its own sealed chamber, and the center chamber has no side wall to take a cup. Putting all three on the rear panel gives a matching set, one cup per chamber.

Wire them at the amplifier end; there is no cross-chamber wiring inside the cabinet.

What is the expected low-frequency extension?

Anechoic F3 is 58.6 Hz per driver with system resonance at 68.2 Hz.

Those figures exclude cabin gain. The cabin adds real output below about 50 Hz, so in-vehicle response runs deeper than the numbers above.

Do I need to add polyfill or damping?

No. Polyfill is already installed as a light wall lining in every chamber, and the quantity is chosen so it does not change the acoustic volume.

Do not add more. Packing a sealed box makes it behave as though it were larger, which moves the alignment away from 0.500 cubic feet per driver.

Are the drivers included?

No. This is an enclosure only. You receive the cabinet finished in plush black carpet with the gloss black acrylic baffle insert, three pre-wired terminal cups on the rear panel, the polyfill lining in place, a threaded insert kit and stainless machine screws.

Bring three matched AudioControl Spike SPK-8 drivers. The cabinet is cut direct fit to them, not a general purpose 8 inch box.

Same series, same size