Sealed, Down Fire, Shallow Mount

PowerBass Subwoofer Boxes and Enclosures

Down fire sealed enclosures cut for PowerBass XL shallow mount subwoofers, CNC-machined in Tullahoma, Tennessee.

PowerBass Subwoofer Boxes and Enclosures

Sealed, Down Fire, Shallow Mount

A shallow mount subwoofer is bought for one reason: there is no room for a normal one. These four cabinets are built around that constraint. All are sealed down fire boxes, cut in Tullahoma, Tennessee to the volumes PowerBass publishes for its own XL shallow mount models, and all sit 1.75 inches off the floor so the cone has a path.

Two sizes, single or dual. Installed height runs 6.65 inches on the single ten to 9.03 inches on the dual twelve, and that is usually what decides the build.

Sealed down fire PowerBass enclosures in ten and twelve inch, single and dual, all Performance Optimized on a 1.5 inch double baffle with polyfill installed.

Cut, assembled and finished in Tullahoma, Tennessee, to the volumes PowerBass publishes for its own XL shallow mount subwoofers.

Driver parameters and recommended volumes are taken from PowerBass published data. We build enclosures to those figures; we do not stock PowerBass drivers and make no claim to represent the brand.

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PowerBass Enclosures at a Glance

Four cabinets, two driver sizes, one shape. All four are sealed down fire boxes on a 1.75 inch standoff, cut to the net volume PowerBass publishes for the model going in them.

Sealed down fire Performance Optimized cabinets for PowerBass XL shallow mount subwoofers.
10 in single10 in dual12 in single12 in dual
DriverXL-1040TTwo XL-1040TXL-1240TTwo XL-1240T
Net volume0.30 cu ft0.30 cu ft per driver0.40 cu ft0.40 cu ft per driver
AlignmentQtc 0.91, F3 53.8 HzQtc 0.91, F3 53.8 HzQtc 1.15, F3 53.6 HzQtc 1.15, F3 53.6 Hz
External W x D x H21.05 x 15 x 4.90 in30.00 x 15 x 5.86 in24.89 x 15 x 5.30 in30.00 x 15 x 7.28 in
Installed height6.65 in7.61 in7.05 in9.03 in
Impedance4 ohms2 or 8 ohms4 ohms2 or 8 ohms
Enclosure weight22 lb32 lb26 lb35 lb

Shared across all four: Langboard Elite MDF cut on ShopSabre routers in Tullahoma, Tennessee. A 1.5 inch double front baffle. Plush black carpet. A Proline X ABS and carbon fibre composite terminal cup with stainless hardware, pre-wired in 12-gauge OFC. Polyfill installed.

Built to the Constraint, Not Around It

There is no alignment ladder on this page. Every cabinet is sealed, every one fires down, and every one is cut to the volume PowerBass recommends for the driver going in it. That leaves two questions: which diameter, and one driver or two.

Down fire is the shape that earns a shallow mount driver its keep. A front firing box still needs the cone facing into open space, so it stands in the cargo area however thin the driver is. Firing at the floor puts the whole cabinet under a seat, and the only height that matters becomes the 6.65 to 9.03 inches these actually occupy.

How to Choose

Start with the space, not the diameter

The single ten is the smallest cabinet here at 6.65 inches installed and the dual twelve the largest at 9.03. Work out what fits first. A twelve you cannot install is worth less than a ten you can.

Understand the extension you are buying

Half power lands at 53.8 Hz on the ten and 53.6 Hz on the twelve. Neither is a subterranean box and neither is trying to be. The volumes are small because the install space is, and firing down at a hard floor is what recovers some of the low end in the vehicle.

Take the twelve's alignment for what it is

At 0.40 cubic feet the XL-1240T runs a Qtc of 1.15, which is firm. Softening it to 0.707 would take about 1.85 cubic feet net, roughly 4.6 times the volume, which defeats the reason for a shallow mount build in the first place. The 0.40 figure is PowerBass's own recommendation and it is the right call for the space.

Then source the driver

We do not stock PowerBass drivers. These cabinets are cut for a subwoofer you already own or buy elsewhere.

Height, Floor and the Driver

Measure the height you actually have

Installed height is the number that matters, not the cabinet height, because these sit on a 1.75 inch standoff. That is 6.65 inches for the single ten, 7.61 for the dual ten, 7.05 for the single twelve and 9.03 for the dual twelve.

Check what is under it

A down fire cabinet loads into the gap between itself and the floor, so it wants a hard flat surface beneath it. Thick carpet and padding, a spare wheel well or a storage lid all change what the driver sees. A sheet of plywood under the cabinet is the usual fix.

Confirm the model, not the diameter

These are cut for the XL-1040T and XL-1240T specifically. A conventional PowerBass ten or twelve has a different mounting depth and a different recommended volume, and will not drop into a shallow mount cabinet.

Installed Height Is the Number That Matters

These sit 1.75 inches off the floor, so the cabinet height on the listing is not what you need to clear. Installed height runs 6.65 inches on the single ten, 7.61 on the dual ten, 7.05 on the single twelve and 9.03 on the dual twelve. Measure to the seat rail or the trunk lid before you choose.

Simple Wiring for Once

Both XL-T models are single four ohm voice coils, not dual coil. One driver is four ohms. A pair is two ohms in parallel or eight in series. There is no coil version to confirm before you buy the amplifier, which is unusual in this category.

Ten or Twelve, Single or Dual

The ten inch cabinets take the XL-1040T at 0.30 cubic feet net and land on a Qtc of 0.91. The twelve inch cabinets take the XL-1240T at 0.40 cubic feet and land on 1.15, a firmer alignment that trades some damping for output in a box that small.

The duals are not two singles joined together. Each driver gets its own sealed chamber cut to the same volume the single delivers, so the alignment is identical whichever you buy. What changes is output, footprint and the load your amplifier sees.

All four cabinets are Performance Optimized down fire boxes. Each product page states the net volume, the alignment and the external and installed dimensions.

PowerBass Subwoofer Box Questions

Which PowerBass subwoofers do these boxes fit?

The ten inch cabinets are cut for the PowerBass XL-1040T and the twelve inch cabinets for the XL-1240T, the shallow mount models in the XL line. Match the model rather than the diameter. A shallow mount driver and a conventional one of the same size do not share a cutout, a mounting depth or a recommended volume.

Do you sell PowerBass subwoofers?

No. We build the enclosure and you source the driver. Every cabinet here is cut to the figures PowerBass publishes for its own XL shallow mount models, so it suits a subwoofer you already own or buy elsewhere.

Why is down fire the right shape for a shallow mount driver?

Because the reason to buy a shallow mount driver is that a conventional box does not fit. Firing at the floor puts the whole cabinet under a seat instead of standing in the cargo area, and these sit 1.75 inches off the floor so the cone has a path. Installed height runs 6.65 inches on the single ten to 9.03 inches on the dual twelve.

How low do these play?

Half power lands at 53.8 Hz on the ten and 53.6 Hz on the twelve, anechoic, before any cabin gain. That is the trade a shallow mount build makes. The volumes PowerBass specifies are small, and small sealed boxes give up extension for size. Firing down at a hard floor close to a boundary is what puts some of it back in the vehicle.

What impedance will I see?

Both XL-T models are single four ohm voice coils, so this is the simplest wiring in the shallow mount category. One driver presents four ohms. Two present two ohms in parallel or eight in series. There is no dual coil version to settle first.

Do these ship with polyfill?

Yes. Every cabinet ships with polyfill already installed. You do not need to add any and you should not remove it, because the fill is part of how the enclosure was tuned.

Can you cut a size you do not list?

Possibly. Everything is CNC cut to order in Tullahoma, Tennessee. Contact us with the PowerBass model and the space you are working with and we will tell you whether we can build it.

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Last updated August 30, 2026