Proline X

Performance Optimized Wedge Ported 10" Enclosure | Sundown Audio SML-Series 10" Thin

Q: Why the 20 degree wedge, and why rear-firing?

The raked face is the seat side. A factory rear seat back leans about 20 degrees off vertical, so the cabinet sits flat against it and uses floor a square box wastes. The baffle stays vertical and fires rearward into the trunk, which acts as the acoustic extension into the cabin. This one is 11.16 inches deep at the base and 6.25 at the top, 30.00 wide and 14 tall.

Q: Do I need a subsonic filter?

Yes, at 28 Hz, 24 dB per octave. Below tuning a vented box stops loading the cone and excursion runs away toward DC. With the filter in place this cabinet puts the Sundown Audio SML-Series 10" Thin at 35 percent of its usable travel at full rated power; without it there is no meaningful number to quote.

Q: How much power can I run, and at what impedance?

Sundown Audio rate the SML-Series 10" Thin at 600 W RMS and that is the thermal ceiling. The Performance Graphs tab shows the mechanical limit, the power at which the cone reaches the end of its travel in this cabinet: here the cone sits at 35 percent of usable travel at the rating, so heat is what stops you, not travel. A D2 coil is 4 ohms in series or 1 ohm in parallel; run series unless the amplifier is rated for 1 ohm. A D4 is 8 series or 2 parallel.

Q: Would a sealed box be better for me?

Below about 23 Hz, yes. The maker's recommended sealed box is louder down there by up to 2.8 dB, because a sealed box rolls off gently where a vented one falls away steeply under tuning. Above that this alignment is the louder of the two for the same power. The Performance Graphs tab plots this cabinet against Sundown Audio's recommended range (low end) sealed box, 0.50 cu ft.

Q: How does the side port work?

It is a triangular slot in the bottom-rear corner: the floor and the raked back wall are two sides, one bevelled panel is the third. It runs across the cabinet, opens into the box through a 2.97 inch gap at the far end and exits through the side panel as the same triangle. Straight, no bend: 25.28 inches of path and 11.7 square inches of channel running at 18.8 metres per second, 53 percent of its turbulence limit. The three mouth edges are rounded over at 1/2 inch, so the opening at the face is 20.9 square inches and the air leaves it at 10.5 metres per second against the 17.0 threshold where a slot port starts to chuff; the panel's throat end is rounded at 3/8 inch for the same reason. The terminal cup is on the other side.

Q: Does this enclosure ship with polyfill?

No, and do not add any. Every sealed Proline X enclosure ships with polyfill; a ported one must not, because damping changes the effective volume the port is tuned against. The port here is cut to 25.28 inches for 35.5 Hz. Stuff it and you move the tuning without shortening the port.

Q: Is the SML-Series 10" Thin included?

No. This is an enclosure only, cut for the Sundown Audio SML-Series 10" Thin specifically: the 9.150 inch cutout, the 3.780 inch mounting depth allowance and the 0.80 cubic foot alignment all come from Sundown Audio's published parameters. It fits both coil versions; the alignment published here is the D2. Bring your own driver.

SKU: PO 10-P W SML10 BB

QUICK SPECS

Alignment: 0.80 cu ft net vented at 35.5 Hz. F3 34.2 Hz anechoic, 0.08 dB passband ripple
Driver: Sundown Audio SML-Series 10" Thin D2, 600 W RMS, 14.0 mm Xmax, 35.21 Hz Fs
Build: Rear-firing wedge, 20 degree rear rake, V-groove and dado joinery, triangular side-exit slot port with a 1/2" rounded mouth, double 1.5" baffle, side-mounted terminal cup
Cabinet: 30.00" W x 13.50" H x 11.16" D at base tapering to 6.25" D at top, 11.7 sq in port, ships dry

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.

$ 369.99

Acrylic Insert Color

In Stock and Ready to Ship

Financing available. Choose Shop Pay Installments at checkout.

Complete Your System

Arc Audio X2 1100.1 Monoblock Subwoofer Amplifier 1100W Class D - Arc Audio Amplifier for car audio systems

Arc Audio Arc Audio X2 1100.1 Monoblock Subwoofer Amplifier | 1100W | Class D $ 758.00

Performance Optimized Wedge Ported 10" Enclosure | Sundown Audio SML-Series 10" Thin

Enclosure Type Ported

External Dimensions 30.00" W x 13.50" H x 11.16" D at base tapering to 6.25" D at top

Gross Volume 1.09 cu ft

Net Volume 0.80 cu ft

Tuning Frequency 35.5 Hz

Port Area 11.7 Square Inches

Weight 41 lbs

Front Panel Thickness 1.5"

INSTALLER'S TAKE

A 0.341 Qts and 23.68 litres of Vas on the SML-Series 10 Thin is a stiff, small motor, and I vent it at 35.5 Hz in 0.803 cubic feet net. The model gives back a 34.2 Hz anechoic F3 on 0.08 dB of ripple, essentially flat. Sundown publishes no sealed figure for this driver, so I have nothing else to weigh it against.

The port is a 5.0 inch leg triangle, 11.7 square inches. At the driver's rated 600 watts the channel runs 18.8 metres per second and the mouth 10.5, under the 17 where a slot port starts to chuff.

This cabinet is cut for the D2 coil, 4 ohms in series or 1 ohm in parallel, and most amplifiers are not stable at 1 ohm, so I default to series unless yours is rated for it. The D4 version of this driver is not built into this box; it needs its own cabinet.

It ships dry. Do not add polyfill to a ported box. Set your subsonic filter at 31 Hz.

Product Details

Proline X Performance Optimized Wedge 10" Ported

The SML-Series 10 Thin vented at 35.5 Hz in 0.803 cubic feet, a 34.2 Hz reach at 6.25 in deep

0.80 cu ft net Tuned 35.5 Hz F3 34.2 Hz Side slot port Cut for the Sundown Audio SML-Series 10" Thin Built in Tennessee

0.80cu ft net

35.5Hz tuning

34.2Hz F3 anechoic

11.7sq in port area

Why this driver is vented at 35.5 Hz

The SML-Series 10 Thin is a 35.21 Hz motor with a 0.341 Qts and 23.68 litres of Vas on 3.78 inches of mounting depth, and the wedge gives it 0.803 cubic feet net vented at 35.5 Hz through an 11.7 square inch port. The cabinet stands 13.5 inches tall and 30 inches wide, running 6.25 inches deep at the top and 11.16 at the base. Sundown publishes no sealed recommendation for this driver, so this vented curve is judged on its own numbers: a 34.2 Hz anechoic F3 on 0.08 dB of ripple, essentially flat.

A 0.341 Qts is a stiff suspension for a 10 inch driver, and 35.5 Hz brings the ripple down to 0.08 dB, essentially flat and well inside the 4.5 dB cap. Sundown does not publish a sealed box for the SML-Series 10 Thin to compare it against. At the driver's rated 600 watts the channel runs at 18.8 metres per second and the mouth at 10.5, under the 17 where a slot port starts to chuff. The shallow 3.78 inch mounting depth is what lets the cabinet run only 6.25 inches deep at the top, with the base at 11.16 set by the port panel clearing the motor at 6.16 inches against 5.52 for the magnet top alone.

Trunk-load wedge, explained

The 20 degree face is the seat side

A factory rear seat back leans about 20 degrees off vertical. The wedge's raked rear panel matches that lean and tucks against it, so the cabinet uses the triangle of trunk floor a square box wastes.

The driver fires rearward

The baffle stays vertical and faces the trunk opening. The trunk acts as the acoustic extension into the cabin; nothing about the driver is angled.

11.16 inches at the base, 6.25 at the top

30 inches wide, 13.5 tall, 6.25 inches deep at the top and 11.16 at the base, 0.803 cubic feet net at 41 pounds.

30.00 inches wide

Width is the wedge's free dimension and it buys two things at once here: airspace, and port length, because the port runs the full width of the box.

The port is the product

The port is a triangular slot in the bottom-rear corner. The floor and the raked back wall are two of its three sides; the third is a single panel bevelled to sit flush against both. It runs across the cabinet, opens into the box at the far end and exits through the side panel: a straight run with no bend, 25.28 inches of centreline path.

The channel is an isosceles triangle with 5.00 inch legs, 11.7 square inches, running at 18.8 metres per second at the tuning frequency. The mouth is that same triangle cut through the side panel with its three edges rounded over at 1/2 inch, so the opening at the face is 20.9 square inches and air leaves it at 10.5 metres per second, against the 17.0 metre per second threshold where a slot port starts to chuff. The panel's throat end carries a 3/8 inch roundover for the same reason.

This enclosure ships dry. Polyfill goes in every sealed Proline X cabinet we build. It does not go in this one. Damping material changes the effective volume the port is tuned against, which moves the tuning away from the 35.5 Hz the port was cut for.

Run a subsonic filter

Below tuning the port stops loading the cone and excursion climbs without limit toward DC, so a 28 Hz high-pass at 24 dB per octave is part of the specification. Set it and the same cabinet takes substantially more power for the same cone travel.

Every wattage on the Performance Graphs tab is a mechanical limit, the power at which the cone reaches the end of its linear travel in this box. What the voice coil can dissipate as heat is a separate ceiling set by Sundown Audio.

Cut for this driver, not for a catalogue

Mounting

Cut to Sundown Audio's published 9.150 inch cutout through a double-layer 1.5 inch baffle, with a cosmetic front layer routed for the acrylic insert. Threaded inserts at every mounting location.

Clearance

This cabinet is cut for the SML-Series 10 Thin's D2 coil, which wires to 4 ohms in series or 1 ohm in parallel; most amplifiers are not stable into 1 ohm, so series is the default unless yours is rated for it. The D4 version of this driver does not fit this cabinet and needs its own box. Mounting depth is 3.78 inches against a 9.15 inch cutout.

Braced

Two windowed C braces run the cabinet profile at the third points of the width and seat on the port panel; the windows keep the cavity one chamber.

Joinery

V-groove and dado throughout, 0.75 inch Langboard Elite MDF, the shell folded from one strip with the sides dropped into dados and the port panel seated in dados of its own.

Power, wiring and warranty

Sundown Audio rate the SML-Series 10" Thin at 600 W RMS. Terminal cup is side mounted on the side opposite the port mouth. A dual 2 ohm driver wired parallel presents 1 ohm, which many amplifiers are not stable into; series at 4 ohm is the safe default unless yours is rated for it.

Performance Optimized carries a 1-year warranty. Built to order in Tullahoma, Tennessee. The driver is not included.

Cut, folded and finished for the Sundown Audio SML-Series 10" Thin. The alignment, the port geometry and the power figures all come from Sundown Audio's published parameters run through our own solver.

Specifications

Series	Proline X Performance Optimized Wedge
Driver-Specific Fitment	Sundown Audio SML-Series 10" Thin D2 (D2)
Enclosure Type	Ported \| Rear-Firing Trunk Wedge
Baffle Configuration	Vertical Baffle - Driver Fires Rearward Into The Trunk
Wedge Angle	20 Degrees On The Rear (Seat-Side) Panel
External Width	30.00 Inches
External Height	13.50 Inches
Top Depth	6.25 Inches
Base Depth	11.16 Inches
Internal Volume (Gross)	1.09 Cubic Feet
Internal Volume (Net After Displacement)	0.80 Cubic Feet
Port Type	Triangular Slot \| Bottom-Rear Corner \| Straight, No Bend \| Side Exit
Port Geometry	Isosceles, 5.00 Inch Legs, 11.7 Square Inches, 25.28 Inches Long, Side Mouth
Port Tuning (Fb)	35.5 Hz
Port Mouth	Triangle Through Side A, 1/2 In Roundover On All Three Edges, 20.9 Square Inches At The Face
Port Throat	Open Far End, 2.97 In Gap To Side B, 3/8 In Roundover On The Panel End
Port Air Velocity	18.8 m/s In The Channel, 10.5 m/s At The Flared Mouth (17.0 m/s Chuff Threshold)
Predicted F3	34.2 Hz (Anechoic)
Passband Ripple	0.08 dB (Anechoic)
Subsonic Filter	28 Hz High-Pass, 24 dB/Octave - REQUIRED On A Vented Enclosure
Driver Fs	35.21 Hz
Driver Qts	0.341
Driver Qes / Qms	0.931 / 2.703
Driver Vas	23.680 Liters / 0.836 Cubic Feet
Driver Sd	346.4 Square Centimeters
Driver Mms	146.99 g
Driver BL	17.43
Driver Re	3.6 Ohm
Driver Xmax	14mm (One-Way)
Driver Displacement	0.04 Cubic Feet (Published by Sundown Audio)
Driver Sensitivity	86.1 dB
Driver Power Handling	600 Watts RMS
Driver Overall Diameter	10.870 Inches (Sundown Audio Spec)
Mounting Depth Required	3.780 Inches (Sundown Audio Spec)
Cutout Diameter	9.150 Inches (Sundown Audio Spec)
Material	Langboard Elite 3/4" MDF
Construction	ShopSabre CNC / Two Windowed C Braces At The Third Points, Seated On The Port Panel
Joinery	V-Groove and Dado (CNC-Cut)
Front Baffle Construction	Double-Layer 1.5" MDF \| Cosmetic Front Layer Routed For The Acrylic Insert
Mounting Hardware	Threaded Inserts At Every Mounting Location \| Stainless Steel Machine Screws Included
Voice Coil Configuration	D2
Terminal Cup	Proline X ABS/Carbon Fiber Composite \| Side Mounted, Opposite The Port \| 12g OFC Pre-Wired
Damping	None - Ships Dry. Polyfill Detunes A Ported Enclosure
Recommended Power	420-600 Watts RMS (Sundown Audio Rated: 600W RMS)
Carpet Finish	Plush Black
Weight	41 lb
Bundle Options	Enclosure Only (Bring Your Own Sundown Audio SML-Series 10" Thin)
Warranty	1-Year Limited (Enclosure)
Manufactured	Tullahoma, Tennessee, USA

Performance Graphs

Net airspace

0.80

cu ft

Tuning

35.5

Hz · Fb

Half power

34.2

Hz · F3, anechoic

Xmax at

5021

W RMS · 28 Hz subsonic

With NO filter

853

W RMS · unfiltered

Port

10.5

m/s at the mouth

01Is this driver right for a ported box?

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

EBP = Fs ÷ Qes = 37.8

Sundown Audio SML-Series 10" Thin D2 · EBP 37.8

Under 50 the raw number leans sealed. The Sundown Audio SML-Series 10" Thin D2 reads 37.8, so this is a ported build against the grain of its own EBP: it works because the alignment is tuned for in-car response rather than for an anechoic curve, and because the cabinet holds port area and volume the driver can actually use.

02What the box does to it

0.80 cu ft net against a 23.7 L Vas, vented at 35.5 Hz.

Fb = 35.5 Hz · F3 = 34.2 Hz · passband ripple 0.08 dB

Sundown Audio SML-Series 10" Thin D2 · Fb 35.5 Hz, F3 34.2 Hz

Anechoic, before any cabin gain, with the 28 Hz subsonic filter already applied. The vent takes over below 36 Hz and the cone stops doing the work there, which is what holds travel down at the bottom of the passband.

03Perceived Ported vs Sealed

This cabinet, 0.80 cu ft net vented at 35.5 Hz, against Sundown Audio's recommended range (low end) sealed box, 0.50 cu ft.

Ported Fb 35.5 Hz · the 0.50 cu ft sealed box runs Qtc 0.56, Fc 58 Hz

Ported · this cabinet, 0.80 cu ft, Fb 35.5 HzSundown Audio's recommended sealed, 0.50 cu ft net, Qtc 0.56

Shaded blue is where the ported alignment is louder for the same power, orange where the sealed one is. The sealed curve is Sundown Audio's recommended range (low end) sealed box, 0.50 cu ft, not this cabinet with the port blocked: two different boxes, because that is the choice a buyer actually has. Across 25 to 60 Hz the vent is worth 6.7 dB at its widest and 4.8 dB on average. This is the anechoic picture, which is not what you hear in a car.

04Real World Ported vs Sealed

The same two boxes with cabin gain applied, 45 Hz corner, 18 dB ceiling.

Flatness across 25–60 Hz: ported 4.2 dB spread, the 0.50 cu ft sealed box 2.7 dB

Ported, in-car · 4.2 dB spreadSundown Audio's recommended sealed, 0.50 cu ft net, in-car · 2.7 dB spread

Cabin gain lifts both boxes by the same amount, so the gap between them does not change: what changes is the shape each one ends up with. A car pressurises below roughly 45 Hz, which fills in the sealed box's shallower rolloff and over-drives it where the ported box is already flat. Across 25 to 60 Hz, the band kick and bass fundamentals occupy, this alignment holds 4.2 dB of spread against 2.7 dB for Sundown Audio's recommended range (low end) sealed box, 0.50 cu ft. The sealed curve is flatter on paper; the ported one trades that for output. Note where the curves cross. Below about 23 Hz the sealed alignment becomes the louder of the two and stays louder all the way down, by up to 2.8 dB: a sealed box rolls off gently into the subsonic region where a vented one falls away steeply once it is below tuning and the vent stops contributing. If the content you are chasing lives below 23 Hz, a sealed alignment reaches further down than this one does. Cabin gain here is a house assumption, not a measurement of your vehicle.

05The 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 Sundown's published 14.0 mm. The two traces are the same cabinet with the subsonic filter switched on and switched off.

P_Xmax = 5021 W with a 28 Hz subsonic · 853 W with none → the filter is worth 5.9×

5021 W · subsonic at 28 Hz, 24 dB/oct853 W · no subsonic filterXmax 14.0 mm one-way, published

Each trace touches the limit and no further, because each is drawn at the exact power that puts the cone on 14.0 mm. With a 28 Hz subsonic that takes 5021 W, reached first at 27 Hz. Take the filter away and the same cabinet reaches 14.0 mm on 853 W — the filter is worth 5.9× the safe power. A vent unloads the cone below tuning, so there is nothing holding it once the box stops loading: on a sealed build a subsonic filter is an improvement, here it is required equipment. The unfiltered trace is still rising where this chart stops at 20 Hz, so treat 853 W as a bound rather than a floor. Every wattage on this page is a MECHANICAL limit, not an electrical one. It is the power at which the cone runs out of linear travel in this cabinet, and nothing more. What the voice coil can dissipate as heat is a separate ceiling set by the driver, not by the box — Sundown rate this one at 600 W RMS, and that is the number that binds first here: heat stops you before travel does, so treat 600 W as the ceiling and the travel figures above as headroom. Final wired impedance, amplifier output and how long you hold the level are all electrical questions this graph does not answer.

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.