Proline X

Proline X Performance Optimized Wedge Enclosure | Fits Dual Kicker Solo X 8" Subwoofers

Q: Will my Kicker Solo X 8s fit this enclosure?

Yes. Each baffle opening is CNC-cut to Kicker's published 7-5/16 inch cutout for the Solo X L7X 8, and each chamber clears the required 7-15/16 inch mounting depth with margin, including breathing room for the vented motors. Both coil versions fit; just use a matched pair.

Q: Why two separate chambers instead of one shared volume?

Because sealed alignment only means something when each driver owns its air. In a shared volume, each cone's compression stroke changes the pressure the other cone sees, which smears transients and blurs the Qtc both drivers were supposed to have. The full-height 3/4 inch divider gives each Solo X 8 its own 0.51 cubic feet at Qtc 0.707, keeps the pair perfectly matched, and stiffens the cabinet as a bonus.

Q: Do both subwoofers need to be the same coil version?

Yes. Run two dual 1-ohm drivers or two dual 2-ohm drivers, never one of each. The chambers are identical, so matched drivers wired identically share power evenly and move in lockstep. Mixing coil versions creates unequal impedances off the shared terminal cup, which splits amplifier power unevenly and unbalances the pair. Pick the coil version whose wiring options land at the final impedance your amplifier wants.

Q: How does a pair of 8s compare to a single 12?

Cone-area math puts two 8s a little under one 12, but the comparison is really about shape and speed. The pair spreads its displacement across two lighter, faster cones and fits a cabinet only 11.75 inches tall, where our single 12 wedge stands 15.25. The 12 digs deeper anechoically with its lower F3; the dual 8s counter with transient snap and a fit-anywhere profile. If your seat clearance is tight, the 8s win before the music even starts.

Q: Will this wedge fit behind the seat of my truck?

You need 25.25 inches of width, 11.75 inches of height, and 14.25 inches of depth at the floor; the top needs only 10 inches thanks to the 20 degree baffle rake. The vertical rear panel sits flat against the cab wall. The low 11.75 inch height is what makes this box work behind seats where taller enclosures will not let the seat latch back.

Q: Are the subwoofers included with this enclosure?

No, this listing is the enclosure only. It is built for a matched pair of Kicker Solo X L7X 8s, which you install using the pressed 8/32 threaded inserts and the two sets of included stainless mounting hardware. If you want help sourcing a pair of Solo X 8s or matching an amplifier, call or text us at 931-563-5151.

SKU: PO 8D-S W Solo X

QUICK SPECS

Alignment: Two identical sealed chambers, 0.51 cu ft net each (1.02 total). Dual 1-ohm 49L7X81s land at Qtc 0.707 (true Butterworth) per chamber, Fc 54 Hz, F3 54 Hz; dual 2-ohm 49L7X82s run Qtc 0.74, F3 52.2 Hz
Chambers: Full-height 3/4 in dado-locked divider, one driver per chamber, doubles as bracing across the 25.25 in span
Drivers: Pair of Kicker Solo X L7X 8s, matched coil versions. Each opening CNC-cut to 7-5/16 in per Kicker spec, 7-15/16 in depth cleared
Wiring: One shared side-mounted terminal cup, 12 gauge OFC to both positions. Kicker recommends 400-800 watts RMS per driver, 800-1600 system
Cabinet: 25.25 in W x 11.75 in H x 10/14.25 in D, 3/4 in Langboard Elite MDF, 1.5 in double baffle plus trim, plush black carpet with black acrylic insert

Shipping Included No freight charges at checkout. What you see is what you pay.

Built in Tennessee CNC cut from 3/4" Langboard Elite MDF. V-groove and dado joinery.

Advanced Terminal Cup Built in-house. ABS/Carbon Fiber. Stainless steel hardware. Copper ring terminals.

$ 399.99

In Stock and Ready to Ship

Financing available. Choose Shop Pay Installments at checkout.

Proline X Performance Optimized Wedge Enclosure | Fits Dual Kicker Solo X 8" Subwoofers

$ 399.99

Enclosure Type Sealed

External Dimensions 25.25" W x 11.75" H x 10" top / 14.25" bottom D (20° wedge)

Net Volume 1.02 total / 0.51 per chambercu ft

Tuning Frequency N/A (Sealed)

Cutout Diameter Direct Fit

Front Panel Thickness 1.5"

Max Mounting Depth Direct Fit

INSTALLER'S TAKE

Two 8s in matched Butterworth chambers is one of the smartest space-to-output plays in car audio. You get roughly 10-inch-class cone area split across two fast, high-excursion drivers, each in its own 0.51 cubic foot chamber at Qtc 0.707, and the pair stays only 11.75 inches tall. About 6 dB more capability than the single 8 with the identical sonic character.

The divider is not decoration. Two drivers sharing one volume modulate each other: every compression stroke from one becomes the other's pressure environment, which smears the alignment both would have alone. A full-height dado-locked wall gives each 8 its own sealed air and doubles as the brace that keeps the 25-inch panels quiet.

Buy both drivers in the same coil version and wire them identically off the shared cup. Mismatched coils or asymmetric wiring splits power unevenly between chambers and undoes the matching the box was built for. Plan 800-1600 clean watts across the pair, 400-800 per driver per Kicker's recommendation.

Fit check: 25.25 wide, 11.75 tall, 14.25 deep at the floor tapering to 10 up top. The low height is the killer feature; this slides behind seats that a taller dual 10 or single 12 wedge cannot, and cabin gain fills in below the mid-50s knee exactly where the alignment leans on it.

Product Details

Performance Optimized Wedge | Dual Kicker Solo X 8

Dual 8" Sealed Wedge Enclosure | Behind-Seat Wedge Design for Two Kicker Solo X L7X 8s

1.22 ft³ Gross0.51 ft³ Net / ChamberQtc 0.707 Butterworth25.25" × 11.75" × 10/14.25"V-Groove / DadoBuilt in Tennessee

Two Kicker Solo X 8s in a Purpose-Built Sealed Wedge

The Solo X L7X 8 packs Kicker's square-cone SoloX architecture and a high-mass ferrite motor into the 8-inch class, and a matched pair in properly solved sealed chambers delivers serious cone area with small-driver speed. This wedge was computed directly from Kicker's factory Thiele/Small parameters, not adapted from a generic dual 8" box.

A 3/4" divider splits the box into two identical sealed chambers, 0.51 cu ft net each after driver displacement. That lands each dual 1-ohm Solo X 8 at a textbook Qtc of 0.707, the true Butterworth alignment, with dual 2-ohm drivers at 0.74 in the same chambers.

Behind-Seat Wedge Design Explained

This is a front-firing wedge built for behind-seat and rear-wall installs. The rear panel is vertical and sits flat against the cab wall; both woofers mount on the baffle, raked back 20 degrees to follow the seat lean.

Vertical Rear Panel

Sits flush against the cab back wall or trunk bulkhead, so the full footprint of the box goes to airspace instead of wasted gaps.

20° Raked Baffle

Matches the lean of most factory seat backs and fires both Solo X drivers forward into the cabin instead of into the seat.

Chambered and Braced

The 3/4" dado-locked center divider isolates each driver in its own sealed chamber and doubles as a full-height brace, killing panel resonance in the largest spans.

Carpet-Wrap Ledge

A recessed perimeter ledge terminates the carpet cleanly at the baffle edge for a finished, factory look.

Engineered for the Kicker Solo X 8

Each chamber is built to 0.51 cubic feet net, the airspace that puts the dual 1-ohm 49L7X81 exactly on the Butterworth alignment. Qtc 0.707 delivers the flattest response and tightest transient control a sealed enclosure can produce: no peaking, no overhang, bass that starts and stops with the recording. Dual 2-ohm 49L7X82 drivers run 0.74 in the same chambers, still squarely inside the accurate, musical zone. Because the chambers are identical, both drivers stay perfectly matched.

Alignment Numbers (Per Driver)

Dual 1-Ohm: Qtc 0.707 · Fc 54 Hz · F3 54 Hz — Dual 2-Ohm: Qtc 0.74 · Fc 54 Hz · F3 52.2 Hz

Mounting Geometry

Each baffle opening is CNC-cut to 7-5/16" (Kicker spec). Mounting depth required is 7-15/16", cleared with margin at every point of the stroke, including breathing room for the vented motor. 8/32 threaded inserts pressed into the baffle backside.

Sealed Alignment Response

Predicted anechoic response of each Solo X 8 in its own 0.51 cu ft sealed chamber, computed from Kicker factory T/S parameters. This enclosure ships without drivers, so both coil variants are plotted; they do not load the same chamber identically.

The dashed line marks the half-power point. Roll-off below F3 is the gentle 12 dB/octave slope characteristic of sealed alignments, which cabin gain in a real vehicle substantially fills in. Run the numbers yourself with our sealed box calculator.

Performance Series Construction, Driver-Specific Tuning

Langboard Elite MDF

Premium 3/4" MDF panels milled to documented spec.

V-Groove and Dado Joinery

CNC-cut V-grooves at every panel intersection. Dado joints lock the raked baffle, vertical rear panel, and center divider into the side walls.

Double-Layer 1.5" Front Baffle

Two bonded 3/4" MDF sheets plus a trim layer at the driver mounting face. Two Solo X 8s put serious mechanical load into the baffle; it does not flex.

Pre-Wired Terminal Cup

Proline X ABS/carbon-fiber composite terminal cup, side-mounted, with 12 gauge OFC pre-wired.

Finish and Trim

Plush Black Carpet

Every enclosure ships wrapped in plush black automotive carpet, the standard finish for the PO Wedge line.

Black Acrylic Insert

The signature Proline X acrylic insert comes in black.

Box-Only

This listing is box-only. Bring your own pair of Solo X 8s.

Wiring Two Kicker Solo X 8s to Your Amplifier

Kicker recommends 400-800 watts RMS per Solo X 8, so plan 800-1600 watts RMS of clean system power across the pair at your wired impedance. Match both drivers to the same coil configuration so the pair loads and wires symmetrically; sealed loading keeps cone travel controlled through the passband.

Built in Tennessee, Backed by Audio Intensity

Manufactured in Tullahoma, Tennessee on our ShopSabre CNC equipment. 1-year limited warranty. Call or text 931-563-5151.

Dual Kicker Solo X 8s: True Butterworth, Twice Over

Two identical 0.51 cubic foot sealed chambers, solved from factory T/S to land each Solo X 8 at Qtc 0.707. Double the cone area, the same flat, tight alignment, in a wedge that disappears behind the seat.

Specifications

Series	Proline X Performance Optimized Wedge
Compatible Driver	Kicker Solo X L7X 8 (49L7X81 / 49L7X82) \| Pair Required
Enclosure Type	Sealed \| Dual Driver \| Front-Firing Wedge
Chamber Configuration	Two Identical Sealed Chambers \| Full 3/4" Divider \| Single Shared Side-Mounted Terminal Cup
Wedge Angle	20 Degrees, Vertical Rear Panel
External Width	25.25 Inches
External Height	11.75 Inches
External Depth (Top)	10 Inches
External Depth (Bottom)	14.25 Inches
Total Internal Gross Volume	1.22 Cubic Feet
Per-Chamber Net Volume	0.51 Cubic Feet
Total Net Volume	1.02 Cubic Feet
System Qtc Per Chamber (Dual 1-Ohm)	0.707 Butterworth
System Qtc Per Chamber (Dual 2-Ohm)	0.74
Predicted Fc Per Driver	54 Hz (D1) / 54 Hz (D2)
Predicted F3 Per Driver (Anechoic)	54 Hz (D1) / 52.2 Hz (D2)
Driver Fs (D1 / D2)	48.0 Hz / 47.95 Hz (Kicker Factory)
Driver Qts (D1 / D2)	0.630 / 0.651 (Kicker Factory)
Driver Vas (D1 / D2)	3.75 L / 4.13 L (Kicker Factory)
Woofer Cutout (Each)	7-5/16 Inches (Kicker Spec)
Mounting Depth Required (Each)	7-15/16 Inches, Cleared With Margin
Recommended Power Per Driver	400-800 Watts RMS (Kicker Recommendation)
Recommended System Power	800-1600 Watts RMS Across The Pair
Material	Langboard Elite 3/4" MDF
Construction	ShopSabre CNC \| V-Groove and Dado Joinery
Panel Thickness	3/4 Inch
Front Baffle	Double-Layer 1.5" MDF Plus Trim Layer
Chamber Divider	3/4" MDF Full-Height, Dado-Locked, Doubles As Brace
Driver Mounting	8/32 Threaded Inserts \| Stainless Machine Screws Included \| 2 Sets
Terminal Cup	One Proline X ABS/Carbon Fiber Composite \| Side Mounted \| Serves Both Chambers
Internal Wiring	12 Gauge OFC, Pre-Wired To Both Driver Positions
Finish	Plush Black Carpet \| Black Acrylic Insert
Bundle Options	Enclosure Only (Bring Your Own Pair of Solo X 8s)
Warranty	1-Year Limited (Enclosure)
Built In	Tullahoma, Tennessee, USA

Performance Graphs

Net airspace

0.51

cu ft per chamber

System Qtc

0.71–0.74

sealed

Half power

52.2–53.8

Hz · F3

Xmax at

2371

W RMS · no filter

With 25 Hz subsonic

2804

W RMS · +18%

Amplifier

400–800

W RMS recommended

This enclosure holds 0.51 cu ft net per chamber. In it the Kicker SoloX L7X 8 (49L7X81) runs a system Qtc of 0.71–0.74 with half power at 52.2–53.8 Hz, and the cone reaches its 24.0 mm travel limit at 2371 W, above the driver’s 800 W thermal rating, so heat stops you before travel does. Run a subsonic filter at 25 Hz and that becomes 2804 W — +433 W, or 18 percent more power for the same 24.0 mm of travel.

01Is it a sealed driver?

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

EBP = Fs ÷ Qes = 62.3–65.3

D1 · EBP 65.3D2 · EBP 62.3

At 62.3–65.3 the SoloX L7X 8 (49L7X81) 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

0.51 cu ft against a 3.8 L Vas.

α = Vas ÷ Vb = 0.26 · Fc = Fs√(α+1) = 54 Hz · Qtc = 0.71–0.74

D1 · Qtc 0.71, Fc 54 Hz, F3 53.8 HzD2 · Qtc 0.74, Fc 54 Hz, F3 52.2 Hz

The box lifts resonance from 48.0 Hz free-air to 54 Hz and half power lands at 52.2–53.8 Hz, anechoic, before any cabin gain. This enclosure ships without a driver, so both coil variants the maker offers are plotted. They do not load the same box the same way.

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

P_Xmax = 2371–2450 W unfiltered → 2804–3018 W with a 25 Hz subsonic

D1 · 2450 W, no filterD2 · 2371 W, no filterD1 · 3018 W with subsonic at 25 Hz, 24 dB/octD2 · 2804 W with subsonic at 25 Hz, 24 dB/octXmax 24.0 mm one-way

Every trace touches the limit and no further, because each is drawn at the exact power that puts that coil on 24.0 mm. Unfiltered that is 2371 W, reached first at 20 Hz. It sits above the 800 W the driver can take thermally, so the voice coil gives up before the suspension does. 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 2804 W before hitting the same 24.0 mm. That is 18 percent more amplifier for the price of one filter setting.

Param	Value	Unit	Note
Fs	48.00 / 47.95	Hz	free-air resonance
Qts	0.631 / 0.651		D1 / D2
Vas	3.75 / 4.13	L	equivalent compliance
Sd	249.6	cm²	effective piston area
Xmax	24	mm	one-way linear travel
Pe	800	W	continuous RMS
SPL	79.4	dB	1 W / 1 m, derived from T/S

Driver parameters as published by Kicker published Klippel T/S sheet. Curves computed against this enclosure’s actual net airspace.

Materials

Material

Built From a Spec Sheet, Not a Sales Sheet

Every Proline X Performance Series enclosure is CNC-cut from Langboard Elite MDF, 3/4" (18mm) panels produced to published mill specifications. Most enclosure manufacturers source generic MDF without published data. We can tell you the internal bond rating, the modulus of elasticity, the modulus of rupture, and the face and edge screw holding strength for every panel in this enclosure, because we chose the material based on those numbers, not on price or availability.

Langboard Elite is produced in the United States. The specifications below are pulled directly from Langboard's published mill data and are verifiable. This is the same panel stock used in our full Proline X lineup.

Specifications

Langboard Elite MDF: Published Mill Data

Property	Value	Why It Matters
Panel Stock	Langboard Elite MDF	Named, verifiable panel source, not generic "high-density MDF"
Thickness	3/4" (18mm)	Industry standard for subwoofer enclosures; panels below this flex under pressure
Density	48.5 lbs/ft³	Higher density = less porosity, better screw retention, reduced resonance
Internal Bond	200 psi	Measures resistance to delamination under sustained internal pressure. The most enclosure-relevant spec on this sheet
Modulus of Rupture (MOR)	4,200 psi	Bending strength before the panel breaks, relevant for larger unsupported baffle spans
Modulus of Elasticity (MOE)	410,000 psi	Stiffness under load; higher MOE means less panel flex under bass pressure, less resonance
Face Screw Holding	325 lbs	How firmly the panel surface holds a screw; critical for baffle joint integrity over time
Edge Screw Holding	250 lbs	Panel edge retention, relevant for every joint that isn't face-to-face

Internal Bond

200 psi: The Number That Actually Matters for Enclosures

The internal bond rating measures how well the MDF panel resists delamination under sustained pressure applied perpendicular to the face. In a subwoofer enclosure, every bass transient generates a pressure pulse that pushes outward on every panel simultaneously. A panel that begins to delaminate internally loses stiffness gradually. The symptoms are slow: a box that starts to sound softer, less defined, less punchy over months of use. 200 psi internal bond is the spec that determines how long this enclosure holds its acoustic integrity under daily use at real power levels.

Stiffness

410,000 psi MOE: Less Flex, Less Resonance

The modulus of elasticity measures panel stiffness, its resistance to bending under load. A stiffer panel flexes less under the pressure generated by a high-excursion driver at volume. Panel flex is a source of acoustic coloration: the panel itself begins to radiate sound at its own resonant frequency, adding distortion to the output. 410,000 psi stiffness combined with V-groove and dado joinery means the panels stay rigid and the bracing controls resonance at the structure level, not the panel level. The bass you hear comes from the driver, not the box.

Screw Holding

325 lb Face / 250 lb Edge: Joints That Stay Locked

Screw holding strength determines how firmly the panel grips a fastener at the face and at the edge. This matters most at the baffle joint, where the front panel meets the side panels and where the driver is mounted. A panel with low screw holding strength allows fasteners to loosen over time under vibration, leading to air gaps at the joint and loss of acoustic seal. 325 lb face screw holding strength means the baffle hardware stays put. Combined with dado joinery and adhesive, the front panel on a Proline X Performance Series enclosure is not going anywhere.

Sourcing

Named Panel Stock: Not "Premium MDF"

The phrase "premium MDF" or "high-density MDF" appears on marketing copy for enclosures across every price point, from $40 to $400. It is not a specification. It is a description with no defined standard. Langboard Elite is a named, sourced, mill-documented product with published data. We name it in our copy because naming it holds us accountable to the spec. You can look up Langboard Elite independently, verify the numbers on this page, and confirm you are getting what we say you are getting. That is the point.

Why Proline X?

Most enclosures are built to a price point. Proline X is built to a spec. Every box starts with published-data MDF, gets CNC-cut to exact internal volume, and is assembled by hand in our Tennessee facility. The difference shows up in the measurements, and in how the box holds up two years into daily use.

CNC-Cut to Spec

Panels are machine-cut on ShopSabre CNC routers and joined with V-groove and dado joinery. Consistent geometry, no hand-cut variance, no gaps at the joints.