Proline X PO 10D-S DF W104ES sealed down fire enclosure, front panel on 1.75 inch feet, 30 by 10.3 inches.

Proline X PO 10D-S DF W104ES sealed down fire enclosure, end panel with recessed terminal cup, 15 by 10.3 inches.

Proline X

Performance Optimized Down Fire Sealed Dual 10" Enclosure | Sony XS-W104ES

Q: Does this fit the Sony XS-W104ES, and will any other 10 inch fit?

The XS-W104ES, yes. The baffle is cut to 9.21 in (234 mm), Sony's published cutout, under the 279 mm (10.98 in) frame. Some dealer listings quote 9-1/16 in; that is 4 mm short of Sony's figure. The 5.39 inch motor clears the cabinet with 4.16 inch to spare, and Sony sells the XS-W104ES in one version, a single 4 ohm coil, so there is no variant to choose. Run two so the chambers match.Any other 10, no. The airspace is engineered around the XS-W104ES's 0.49 Qts and 23.3 liters of Vas, and a different woofer that happened to drop into the hole would not see the alignment printed on this page.

Q: Why 0.76 cubic feet per chamber, and what alignment does it target?

It is the Butterworth volume on Sony's published Fs 39.6 Hz, Qts 0.49 and Vas 23.3 liters: system Qtc 0.707, maximally flat, with resonance and half power both at 57.1 Hz. Sony's own sheet recommends 1.01 cubic feet sealed, which reads Qtc 0.66 on the same figures; this cabinet is built to the flatter Butterworth box.One caveat: a review sample measured after break-in read Qts 0.43 and Vas near 33 liters, looser than Sony's sheet. On those numbers this cabinet reads Qtc 0.68, a touch more damped. Either way it is a well-behaved sealed alignment.

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

Sony rates the XS-W104ES at 450 watts RMS per driver to CTA-2031 and 1800 watts short-term maximum, so target 315 to 450 watts RMS per driver at the final load.Each XS-W104ES has a single 4 ohm voice coil (3.8 ohms DC). Two in parallel present 2 ohms; two in series present 8 ohms. Wire both the same way, and check that your amplifier is rated for the load you choose. Confirm your amplifier's minimum stable impedance first.

Q: How tall is this once the standoffs are on?

The cabinet is 10.30 inches tall measured in the down fire position, and that figure excludes the standoffs. The standoffs hold 1.75 inches under the baffle, so plan your space around a finished stack of roughly 12.05 inches.The footprint is the standard Performance Optimized down fire platform, 30.00 inches wide by 15.00 deep. Height is the only dimension solved to the driver.

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

Two drivers sharing one sealed volume load each other: each driver's compression stroke becomes the pressure the other works against, which blurs the alignment either would have alone. A bonded full-height 3/4 inch divider gives each driver its own 0.76 cubic feet and its own polyfill.It also means a failure in one driver does not unload the other, and the alignment on this page is the alignment in each chamber, not an average across a shared box.

Q: What is the expected low-frequency extension?

Anechoic F3 is 57.1 Hz per chamber with system resonance at 57.1 Hz. At Qtc 0.71 the response is maximally flat into the rolloff, so F3 and fc coincide.Those figures exclude cabin gain. In a car the cabin's transfer function adds real output below 50 Hz, so in-vehicle response runs deeper than the numbers above.

Q: Do I need to add polyfill or damping?

No. Polyfill is already installed in both chambers as a light wall lining to control internal reflections, and the quantity is chosen so it does not change the acoustic volume.Do not add more. Packing a sealed box with fill makes it behave as though it were larger, which walks the alignment away from the 0.76 cubic feet per chamber this cabinet was built to.

Q: Is the driver included, and are the threaded inserts installed?

No driver. This is an enclosure only. You receive the cabinet finished in plush black carpet, one side-mounted pre-wired terminal cup to both positions, the polyfill lining already in place, the standoffs, and a threaded insert kit with stainless machine screws.The inserts ship loose on purpose: Sony prints no bolt circle for the XS-W104ES, so you set the driver in the recess, mark its holes, drill and press the inserts. The pair of Sony XS-W104ES is purchased separately, and the cabinet is cut direct fit to it, not a general purpose 10 inch box.

SKU: PO 10D-S DF W104ES

QUICK SPECS

Alignment: 0.76 cu ft net per chamber, Qtc 0.707, F3 57.1 Hz
Drivers: Pair of Sony XS-W104ES, 450 W RMS each, 6.5 mm Xmax, 5.39 in mounting depth
Chambers: Two fully separate sealed chambers, 3/4" MDF full divider, one shared side-mounted terminal cup
Standoffs: Included, 1.75 in, shipped uninstalled. Installed height near 12.05 in
Cabinet: 30.00"W x 15.00"D x 10.30"H in down fire position, excludes standoffs, square corners

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.

$ 299.99

In Stock and Ready to Ship

Financing available. Choose Shop Pay Installments at checkout.

Performance Optimized Down Fire Sealed Dual 10" Enclosure | Sony XS-W104ES

$ 299.99

Enclosure Type Sealed

External Dimensions 30.00" W x 15.00" D x 10.30" H (measured in down fire position, excludes standoffs)

Gross Volume 1.73 cu ft

Net Volume 1.52 cu ft

Shipping Weight 44 lbs

Front Panel Thickness 1.5"

INSTALLER'S TAKE

Measure the installed height, not the cabinet height. The box is 10.30 tall on its own and the standoffs add 1.75, so plan around 12.05 inches of stack on the 30 by 15 footprint.

Airspace set the height here, 0.76 cubic feet per chamber at Butterworth; the motors clear the lid with 4.16 to spare.

Floor slot is 0.90 times the cone area at the 1.75 standoff, a little under the 1.0 I like. With 6.5 mm of excursion this cone does not move much air, so it costs little; taller feet fix it if the floor allows.

Cut is 9.21 (234 mm), Sony's own figure. Some dealer pages say 9-1/16; that is 4 mm short and the basket will not drop in.

Inserts ship in the kit, not pressed: Sony prints no bolt circle for this driver. Mark from the driver, drill, press. It is sealed, so leave the polyfill as it is and run it at 450 watts or under.

Product Details

Proline X Performance Optimized Down Fire Dual 10" Sealed

Cut and tuned for a pair of Sony XS-W104ES

V-Groove and DadoLangboard Elite MDF1.52 cu ft Net TotalSeparate ChambersStandoffs Included

0.76cu ft net per chamber

0.707system Qtc per chamber

57.1 HzF3 rolloff, anechoic

10.30 incabinet height, excludes standoffs

Performance, Performance Optimized, and Micro

Proline X builds three tiers of Down Fire enclosure. The difference is not finish or materials, it is whether the cabinet was designed for a category or for a driver, and how much of the fitting work is already done for you.

	Performance	Performance Optimized	Micro Series
Fitment	Universal. Accepts any subwoofer that clears the published cutout and mounting depth.	Woofer specific. Cut for one named subwoofer, with cutout, mounting depth, magnet clearance and displacement drawn in CAD from that driver.	Woofer specific. Cut for one named subwoofer.
Footprint	Sized to the driver diameter.	A shared 30 by 15 inch platform, with cabinet height as the variable. This build sits on that platform at 10.30 inches tall, the height that gives each driver its own 0.76 cubic feet.	Compact per driver footprint.
Front baffle	Single, 3/4 inch.	Double, 1.5 inch, outer layer machined as a flush recess.	Double, 1.5 inch.
Driver mounting	Solid flange. You drill your own mounting holes.	Threaded insert kit and stainless machine screws included; Sony prints no bolt circle, so you mark and drill from the driver.	Threaded inserts, stainless machine screws included.
Joinery	V-groove and dado, CNC cut.	V-groove and dado, CNC cut, full-height divider and perimeter cross brace.	Stack fab, dowel reinforced.
Published alignment	Modeled Qtc profiles across a range of drivers. No single response curve.	A real predicted Qtc and F3 for that exact driver, calculated from its own Thiele-Small parameters.	Target alignment described in the listing.
Carpet	Gray standard, black optional.	Plush black.	Plush black.
Warranty	1 year limited.	1 year limited.	2 years.

Feet ship with every tier, uninstalled on purpose. Mount them where your floor wants them for a down fire install, or leave them off and run the cabinet front firing or up firing. The orientation is yours to choose.

This page is a Performance Optimized enclosure. The airspace, the cutout and the cabinet height all come from the driver's own numbers. A Performance box fits your subwoofer. A Performance Optimized box was built for it.

Built Around a Pair of Sony XS-W104ES

Nothing about this cabinet is generic. The baffle is cut to 9.21 in (234 mm), Sony's published cutout, under the 279 mm (10.98 in) frame. Some dealer listings quote 9-1/16 in; that is 4 mm short of Sony's figure. The airspace lands on 0.76 cubic feet net per chamber, the Butterworth volume on Sony's figures.

The XS-W104ES is the 10 inch of Sony's Mobile ES line: an MRC honeycomb cone and a single 4 ohm voice coil, rated 450 watts RMS to CTA-2031 and 1800 watts short-term maximum, with 6.5 mm of one-way excursion. It is 5.39 inches deep on a 10.98 inch frame, which matters on a down fire, where the motor rises into the cabinet. Every figure comes from Sony's published XS-W104ES parameters, and they hold together: Qes and Qms reproduce the printed Qts, and the 129 g moving mass and 0.125 mm/N compliance reproduce the 39.6 Hz resonance and 23.3 liter Vas. A review sample measured after break-in read looser, Qts 0.43 and Vas near 33 liters; on those numbers this cabinet reads Qtc 0.68 instead of 0.71, so treat the alignment as a range a few hundredths wide.

Two Chambers, Not One Volume

This enclosure follows the Proline X standing rule for dual sealed builds: two fully separate chambers split by a bonded full height 3/4 inch MDF divider, each driver in its own 0.76 cubic feet with its own polyfill.

Two drivers sharing one sealed volume interact acoustically. Each driver's compression phase becomes the pressure environment the other is working against, which smears transient response and blurs the alignment either would have on its own. A full divider removes that entirely. One shared side mounted terminal cup feeds both driver positions, so the cabinet stays a single connection point.

Net Volume, Not Gross

Each chamber is built at 0.76 cubic feet net per driver, out of 1.73 gross after the divider and an estimated 2.3 liter driver displacement. At 0.76 cubic feet the XS-W104ES lands at Qtc 0.707, maximally flat, with system resonance and half power both at 57.1 Hz. Sony's own sheet recommends 1.01 cubic feet sealed, which reads Qtc 0.66 on the same figures; this cabinet is built to the flatter Butterworth box.

True net, not marketing net. Internal volume is calculated from the machined cavity dimensions and the driver's displacement (an estimate here, since Sony publishes none), not guessed from external dimensions minus wall thickness.

Driver (per chamber)	System Qtc	fc	F3
XS-W104ES, single 4 ohm	Qtc 0.707	57.1 Hz	57.1 Hz

Down Fire Construction

Cut with V-groove and dado joinery on our ShopSabre routers from Langboard Elite 3/4 inch MDF. Every panel joint is a machined interlocking groove that mechanically locks before adhesive is applied, which keeps the cabinet airtight under sustained pressure cycling. Corners are square on Down Fire cabinets.

The cabinet measures 30.00 inches wide by 15.00 inches deep by 10.30 inches tall, measured in the down fire position and excluding standoffs. Plan the space around the installed height rather than the cabinet height: the standoffs hold 1.75 inches under the baffle, so the finished stack sits near 12.05 inches.

Double Baffle, Flush Recess

The front baffle is 1.5 inches, two bonded 3/4 inch sheets, with the outer layer machined as a flush recess so the driver bolts to the inner layer. That recovers 3/4 inch of internal clearance.

Side-Mounted Terminal Cup

Proline X ABS and carbon fiber composite cup with stainless hardware and copper ring terminals, pre-wired in 12 gauge OFC to both driver positions. Side mounted so it stays accessible with the baffle facing the floor.

Standoffs Included

Sony publishes no front clearance figure for the XS-W104ES, so this cabinet uses the Proline X standard 1.75 inch standoff, shipped with every enclosure and left uninstalled so you can place them to suit your floor. At that height the floor slot is 0.90 times the cone area, a little under the 1.0 we aim for. With 6.5 mm of excursion the cone moves only 235 cubic centimeters at its limit, so the smaller opening costs little, and taller feet or a front-firing install remove it entirely.

Motor Clearance and Orientation

The motors rise off the baffle into the cavity, so on a down fire cabinet the clearance that matters runs to the top panel. The 5.39 inch mounting depth puts the motor 3.89 inches into a 8.05 inch cavity, leaving 4.16 inches above the motor against a 0.75 inch minimum. Height was set by the airspace, above the minimum the clearance alone would have required.

Sony does not publish a position on down firing this driver, and this cabinet makes no claim on their behalf. The feet ship uninstalled, so if you would rather run it front firing or up firing, that is a decision you can make at install time without changing anything about the enclosure.

Power, Mounting and Warranty

Sony rates the XS-W104ES at 450 watts RMS to CTA-2031 and 1800 watts short-term maximum, 900 watts RMS combined. Each XS-W104ES has a single 4 ohm voice coil (3.8 ohms DC). Two in parallel present 2 ohms; two in series present 8 ohms. Wire both the same way, and check that your amplifier is rated for the load you choose. Confirm the load against your amplifier's minimum stable impedance before powering the system.

Sony prints no bolt circle for the XS-W104ES, so the baffle ships undrilled with a threaded insert kit and stainless machine screws: set the driver in the recess, mark its holes, drill, press the inserts and bolt it down. The enclosure carries a 1 year limited warranty. Bring your own pair of XS-W104ES; the drivers are purchased separately.

Cut for the Driver, Not the Catalog

Built one at a time in Tullahoma, Tennessee, with standoffs and a 1 year limited warranty. Questions on fitment or amplifier matching, call 931-563-5151.

Specifications

Specification	Value
Series	Proline X Performance Optimized Down Fire
Compatible Driver	Sony XS-W104ES (Mobile ES), quantity 2. Direct fit
Configuration	Dual 10 inch, two separate chambers, sealed down fire
Mounting Position	Trunk or cargo floor, baffle facing down on standoffs
Firing Direction	Downward. Feet ship uninstalled, so front or up firing is also possible
External Width	30.00 in
External Depth	15.00 in
External Height	10.30 in in the down fire position, excludes standoffs
Installed Height	12.05 in including the 1.75 in standoff
Internal Volume, Gross	1.73 cu ft total
Internal Volume, Net Acoustic	0.76 cu ft per chamber after the divider and an estimated 2.3 L displacement per driver
Height Set By	Airspace; clearance alone would allow a lower cabinet
Driver Mounting Depth	5.39 in required, 4.16 in clearance above the motor
Floor Slot	0.90 times the cone area at the 1.75 in standoff
Alignment per chamber	Qtc 0.707, fc 57.1 Hz, F3 57.1 Hz anechoic; about 0.68 on a broken-in sample measured at Qts 0.43, Vas 33 L
Sony Recommended Enclosure	1.01 cu ft sealed (Qtc 0.66), 1.44 cu ft ported
Woofer Opening	9.21 in (234 mm), two, Sony's published cutout
Frame Outer Diameter	10.98 in (279 mm)
Bolt Circle	Not printed by Sony; threaded insert kit included
Driver Displacement	2.3 L / 0.081 cu ft, estimated; Sony publishes none
Fs / Qts / Qes / Qms	39.6 Hz / 0.49 / 0.52 / 7.03
Vas / Mms / Cms / Bl	23.3 L / 129 g / 0.125 mm/N / 15.4 N/A
Driver Sd	362 cm2, published by Sony
Xmax	6.5 mm one way, Sony spec
DC Resistance	3.8 ohm
Driver Sensitivity	86 dB at 1 W / 1 m, Sony spec (IEC 60268-5)
Driver Power Handling	450 W RMS (CTA-2031) / 350 W rated (IEC) / 1800 W short-term maximum per driver
Wiring Options	Single 4 ohm coil; two drivers give 2 ohm in parallel or 8 ohm in series
Parameter Source	Sony XS-W104ES published parameters (Loudspeaker Database transcription) and Sony Instructions
Material	Langboard Elite MDF
Construction	CNC cut, V-groove and dado joinery, square corners
Panel Thickness	0.75 in
Front Baffle	1.5 in double baffle, outer layer machined as a flush recess
Internal Bracing	Full-height 3/4 in divider
Driver Mounting	Threaded insert kit included, NOT pre-installed: Sony prints no bolt circle
Terminal Cups	One Proline X ABS and carbon fiber composite, side mounted, pre wired 12 gauge OFC to both driver positions
Standoffs	Included, 1.75 in, shipped uninstalled
Damping	Light polyfill wall lining in both chambers, does not alter acoustic volume
Carpet	Plush black
Shipping Weight	44 lb
Warranty	1 Year Limited
Built In	Tullahoma, Tennessee

Performance Graphs

Net airspace

0.76

cu ft per chamber

System Qtc

0.71

sealed

Half power

57.1

Hz · F3

Xmax at

W RMS · no filter

With 25 Hz subsonic

116

W RMS · +20%

Amplifier

450

W RMS recommended

This enclosure holds 0.76 cu ft net per chamber. In it the Sony XS-W104ES runs a system Qtc of 0.71 with half power at 57.1 Hz, and the cone reaches its 6.5 mm travel limit at 97 W, below the driver’s 450 W thermal rating, so travel is what stops you here, not heat. Run a subsonic filter at 25 Hz and that becomes 116 W — +19 W, or 20 percent more power for the same 6.5 mm of travel.

01Is it a sealed driver?

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

EBP = Fs ÷ Qes = 76.2

single 4 ohm · EBP 76.2

At 76.2 the XS-W104ES 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

0.76 cu ft against a 23.3 L Vas.

α = Vas ÷ Vb = 1.08 · Fc = Fs√(α+1) = 57 Hz · Qtc = 0.71

single 4 ohm · Qtc 0.71, Fc 57 Hz, F3 57.1 Hz

The box lifts resonance from 39.6 Hz free-air to 57 Hz and half power lands at 57.1 Hz, anechoic, before any cabin gain. Figures are Sony’s published XS-W104ES parameters, and they hold together: Qes and Qms reproduce the printed Qts, and the moving mass and compliance reproduce the 39.6 Hz resonance and 23.3 liter Vas. Driver displacement is not published; 2.3 liters is an estimate. Each chamber of this dual down fire holds 0.76 cubic feet, the Butterworth volume on Sony’s figures, the same airspace as the wedge versions.

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

P_Xmax = 97 W unfiltered → 116 W with a 25 Hz subsonic

single 4 ohm · 97 W, no filtersingle 4 ohm · 116 W with subsonic at 25 Hz, 24 dB/octXmax 6.5 mm one-way

Every trace touches the limit and no further, because each is drawn at the exact power that puts that coil on 6.5 mm. Unfiltered that is 97 W, reached first at 20 Hz. It sits under the 450 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 116 W before hitting the same 6.5 mm. That is 20 percent more amplifier for the price of one filter setting.

Param	Value	Unit	Note
Fs	39.60	Hz	free-air resonance
Qts	0.490		single 4 ohm
Vas	23.30	L	equivalent compliance
Sd	362.0	cm²	effective piston area
Xmax	6.5	mm	one-way linear travel
Pe	450	W	continuous RMS
SPL	86.3	dB	1 W / 1 m, derived from T/S

Driver parameters as published by Sony XS-W104ES specification 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.