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

The Down Fire Wide Format

Down Fire Wide is the Performance Optimized answer to a specific problem: the space under the rear seat of a truck or SUV, or a narrow cargo floor, is long and shallow, and a 30 by 15 inch Down Fire cabinet will not go in it.

So the cabinet is turned sideways. This one runs 41 inches wide by 12 inches deep by 9.625 inches tall. It is the same Sony XS-W104ES, in a cabinet 3 inches shallower front to back than our standard 30 by 15 inch Sony XS-W104ES cabinet and 11 inches longer. The airspace given up in depth is recovered along the length, so each driver still gets a properly sized chamber rather than a compromised one.

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.

Built Around a Pair of Sony XS-W104ES

Nothing about this cabinet is generic. Both baffle positions are 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 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, so treat the alignment below as good to a few hundredths rather than to the third decimal.

Two Chambers, Not One

This enclosure follows the Proline X standing design rule for dual sealed builds: two fully separate chambers divided by a bonded full-height 3/4 inch MDF panel.

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 each would have on its own. A full divider eliminates that entirely. Each XS-W104ES gets its own 0.765 cubic feet net and its own polyfill.

On a long cabinet the divider does structural work as well, tying the front and rear walls together at the centre of a 41 inch span. 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 0.765 cubic feet net, 1.530 cubic feet net total, out of 1.725 gross after the divider and an estimated 0.081 cubic foot (2.3 liter) displacement per driver. Sony publishes no displacement figure for this driver, so that number is our estimate.

At 0.765 cubic feet the XS-W104ES lands at Qtc 0.706, Fc 57.1 Hz, F3 57.1 Hz: essentially maximally flat, with system resonance and half power at the same frequency. Sony's own sheet recommends a larger sealed box, which reads more damped on the same figures; this cabinet is built to the flatter Butterworth volume.

Height is the free dimension. With the footprint fixed at 41 by 12, the cabinet height was solved to put each chamber on the 0.76 cubic feet the standard cabinet holds, then rounded up to the next sixteenth so the airspace lands on the target rather than under it. The motor clears the top panel by 3.48 inches against our 0.75 inch minimum, so airspace set the height here, not clearance.

Down Fire Wide Construction

Cut with V-groove and dado joinery on our ShopSabre routers from Langboard Elite 3/4 inch MDF, a dense 48.5 lb/ft³ board with a 200 psi internal bond and 410,000 psi MOE. Every panel joint is a machined interlocking groove that mechanically locks before adhesive is applied, which keeps both chambers airtight under sustained pressure cycling. Corners are square on Down Fire cabinets.

The cabinet measures 41 inches wide by 12 inches deep by 9.625 inches tall, measured in the down fire position and excluding standoffs. The 1.75 inch standoffs ship uninstalled so you can place them to suit your floor; installed, the finished stack is 11.375 inches. Plan the space around that figure, not the cabinet height.

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 7.375 inch cavity, leaving 3.48 inches above the motor against a 0.75 inch minimum. Height was set by the airspace, well above the minimum the clearance alone would have required.

At the 1.75 inch standoff 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. Sony does not publish a position on down firing this driver, and this cabinet makes no claim on their behalf.

Power and Wiring

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 through the shared cup present 2 ohms; two in series present 8 ohms. Wire both the same way and confirm the load against your amplifier's minimum stable impedance before powering the system.

Bring your own pair of XS-W104ES; the drivers are purchased separately. The enclosure carries a 1 year limited warranty.