Sealed, Three Chassis, 11 to 15 Inch

Stereo Integrity Subwoofer Boxes and Enclosures

Sealed enclosures cut for Stereo Integrity subwoofers in wedge, standard and down-fire, CNC-machined in Tullahoma, Tennessee.

Proline X subwoofer enclosures built for Stereo Integrity subwoofers.

Sealed, Three Chassis, 11 to 15 Inch

Three drivers, three cabinet shapes, and for two of them the shape is a free choice. The SQL-12 comes as a standard box or a wedge. The BM-11 comes as a down-fire cabinet or a wedge in single, dual or triple.

Both options hold the same airspace, which means the alignment does not change with the shape. Pick the one that fits the vehicle and the sound follows.

Sealed Stereo Integrity enclosures for the SQL-12, SQL-15 and BM-11, single through triple, in wedge, standard and down-fire, all on a 1.5 inch double baffle.

Cut, assembled and finished in Tullahoma, Tennessee, to the cutout and mounting depth Stereo Integrity publish for each driver.

Driver parameters and fitment dimensions are taken from Stereo Integrity published data, with the BM-11's total Q cross-checked against loudspeakerdatabase and a ResoNix Klippel measurement. We build enclosures to those figures; we do not stock Stereo Integrity drivers and make no claim to represent the brand.

Shop the Lineup

←
→

All products loaded

Same Driver, Same Airspace, Different Shape

Two of these three drivers are offered in more than one cabinet shape, and both shapes hold the identical airspace. That means the alignment does not change: a Stereo Integrity SQL-12 in our standard box and in our wedge produce the same Qtc and the same F3. The shape decides where the cabinet fits in the vehicle, not how it sounds.

Nine sealed Performance Optimized cabinets, three chassis, three drivers.
ChassisGoes whereDrivers offeredPrice from
WedgeTrunk or cargo area, leaning on the rear seat backSQL-12, SQL-15, BM-11$259.99
StandardTrunk, upright rectangular boxSQL-12$299.99
Down FireUnder or behind a seat, fires at the floorBM-11$239.99

The Three Drivers

Every cabinet is cut to one specific model. Alignment below is computed from Stereo Integrity published Thiele-Small parameters at the airspace each cabinet holds.

Alignment per driver. All figures anechoic, before cabin gain.
DriverNet per driverQtcF3Offered as
SQL-121.00 cu ft0.76442.6 Hzstandard or wedge, single or dual
SQL-152.00 cu ft0.81641.8 Hzwedge, single
BM-110.40 cu ft1.43241.5 Hzdown fire or wedge, single, dual or triple

Shared across every cabinet: 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. Threaded inserts at every mounting location. Polyfill installed.

Shape Is a Fitment Decision, Not an Acoustic One

Where a driver is offered in more than one cabinet here, both cabinets hold the identical net volume. A SQL-12 in the standard box and a SQL-12 in the wedge both run Qtc 0.764 with half power at 42.6 Hz. The wedge leans on the seat back and keeps the trunk floor usable; the standard box is a simple upright rectangle. Neither sounds different.

The same is true of the BM-11: down-fire at 0.40 cubic feet or wedge at 0.40, same Qtc 1.432 either way. Its 3.071 inch mounting depth is what makes both shapes possible.

How to Choose

Driver first, this time

Unusually for one of our brand pages, the driver is the decision that matters and the shape is the easy one. SQL for a damped alignment and real excursion, BM-11 for an install with no room.

Then the shape, on fitment alone

Both shapes offered for a given driver hold the same airspace, so there is no acoustic penalty either way. Choose on where it goes.

Count is about output, not character

Every chamber in a dual or triple is cut to the same volume the single delivers, so the alignment is identical. What changes is output, cabinet size and the amplifier load.

Then source the driver

We do not stock Stereo Integrity drivers. Every cabinet is cut for a subwoofer you already own or buy elsewhere.

Measuring for One

Wedge: measure the trunk floor

A wedge is deepest at its base and that base dimension has to clear on the trunk floor. Widths run from 16.74 inches on the single BM-11 to 40 inches on the triple.

Down fire: measure height

The BM-11 down-fire cabinet stands on a 1.75 inch standoff and wants a hard flat floor beneath it. Installed height, not cabinet height, is the number to check.

Standard: measure everything

The standard SQL-12 boxes are upright rectangles, 20 inches wide for the single and 31 for the dual, both 15 inches tall and 13.625 deep.

The Shape Does Not Change the Sound

Where a driver is offered in two cabinet shapes here, both hold the same net airspace, so both produce the same Qtc and the same F3. Choose the shape on where it fits in the vehicle. The acoustics are already settled by the volume.

The BM-11 Q Is Disputed, and We Say So

Stereo Integrity publish a total Q of 0.73 for the BM-11, loudspeakerdatabase carries 0.83, and a ResoNix Klippel measurement gives 0.85. Our figures use 0.83. At 0.40 cubic feet those give a system Qtc of 1.26, 1.43 and 1.47, so the cabinet is under-damped on every reading. We would rather print which number we used than pick the flattering one.

SQL or BM

The SQL cabinets are the damped ones. SQL-12 at Qtc 0.764 and SQL-15 at 0.816, both with 26 mm of one-way travel and a 1000 watt rating behind them. If you want a flat sealed alignment with real excursion, that is the pair.

The BM-11 is a different proposition. An 11 inch cone on a 3.071 inch mounting depth, so it fits where nothing else does, and it reaches 41.5 Hz doing it. The trade is the alignment: Qtc 1.432 is peaked, not flat, and no small sealed cabinet changes that.

Driver-matched

Performance Optimized Series

Both cabinets

The build standard for both cabinets: a 1.5 inch double baffle cut to the published alignment of one driver rather than to a size class.

Cut to one driver

For detail

Single-driver cabinet

Twelve inch

The choice when the subwoofer is there to finish a front stage and the cargo area still has to be usable.

Sealed

For headroom

Dual-driver cabinet

Twelve inch

Two drivers, each in its own chamber cut tighter than the single equivalent so the cabinet still fits a real space.

Sealed

Every cabinet is Performance Optimized. Where a driver is offered in two shapes both hold the same airspace, so the alignment is identical.

Categories

Keep Reading

Supporting guides to help you design, build, and tune your system.

Stereo Integrity Subwoofer Box Questions

Which Stereo Integrity subwoofers do these boxes fit?

Three models. The SQL-12 in a standard box or a wedge, single or dual. The SQL-15 in a wedge. The BM-11 in a wedge or a down-fire cabinet, and the wedge is offered as a single, a dual or a triple. Each product title names the exact model it is cut for.

Does the cabinet shape change how it sounds?

No, and that is deliberate. Where a driver is offered in two shapes, both hold the same airspace, so the alignment is identical. The SQL-12 runs Qtc 0.764 and F3 42.6 Hz in the standard box and in the wedge alike. Choose the shape that fits your vehicle.

Which is the better low-end performer?

They are closer than the diameters suggest. The SQL-15 reaches 41.8 Hz, the SQL-12 42.6 Hz and the BM-11 41.5 Hz, all anechoic. The real difference is character: the two SQL cabinets are well damped at Qtc 0.764 and 0.816, while the BM-11 runs 1.432, which is a peaked alignment rather than a flat one.

Why is the BM-11 alignment so high?

Because of the driver, not the cabinet. Its total Q is high enough that no small sealed box brings the system below about 1.2. Sources also disagree on the exact figure: Stereo Integrity publish 0.73, loudspeakerdatabase carries 0.83 and a ResoNix Klippel measurement gives 0.85. We compute from 0.83 and say so on the listing. The alignment is under-damped on all three readings, so the disagreement changes the decimal and not the character. What you get in return is 41.5 Hz from a cabinet under five inches deep at the front.

Do you sell Stereo Integrity subwoofers?

No. We build the enclosure and you source the driver. Every cabinet is cut to the cutout and mounting depth Stereo Integrity publish for that model.

Can I run three BM-11s?

Yes. The triple is a 40 inch wide wedge with three fully separate 0.40 cubic foot chambers. It is the only triple driver enclosure in the Performance Optimized range outside the 8 inch cabinets. Work the impedance out first: three dual 2 ohm drivers is six coils, and the two clean answers are 1.33 ohms or 3 ohms.

Drivers Built to Match

12 Inch Subwoofers We Do Stock

The drivers below are matched to the enclosures above by Thiele-Small parameters. Buying together guarantees the alignment, port tuning, and damping work the way the engineering intended.

Prodigy Audio 12 inch Subwoofer NB2 Series - Prodigy Subwoofer for car audio systems

Prodigy Audio

Prodigy Audio 12 inch Subwoofer | NB2 Series

$ 150.99 $ 161.99
Image Dynamics ID12 V4 12 inch Subwoofer

Image Dynamics

Image Dynamics ID12 V4 12 inch Subwoofer

$ 159.99
Arc Audio X2V2 12-inch Subwoofer

Arc Audio

Arc Audio X2V2 12" Subwoofer

$ 229.00
Image Dynamics IDQ12 V4 12 inch Subwoofer

Image Dynamics

Image Dynamics IDQ12 V4 12 inch Subwoofer

$ 280.99

View all 12 inch subwoofers | Need a custom build? Contact us

Drivers Built to Match

10 Inch Subwoofers We Do Stock

The drivers below are matched to the enclosures above by Thiele-Small parameters. Buying together guarantees the alignment, port tuning, and damping work the way the engineering intended.

Prodigy Audio 10 inch Subwoofer NB2 Series - Prodigy Subwoofer for car audio systems

Prodigy Audio

Prodigy Audio 10 inch Subwoofer | NB2 Series

$ 138.99 $ 145.99
Image Dynamics ID10 V4 10-inch Subwoofer

Image Dynamics

Image Dynamics ID10 V4 10-inch Subwoofer

$ 139.99
Prodigy Audio 10 inch Subwoofer NB3 Series - Prodigy Subwoofer for car audio systems

Prodigy Audio

Prodigy Audio 10 inch Subwoofer | NB3 Series

$ 148.99 $ 165.99
Sony XS-W104ES Mobile ES Series 10-inch 4-ohm component subwoofer

Sony

Sony XS-W104ES Mobile ES Series 10" 4-ohm component subwoofer

$ 198.00 $ 299.99

View all 10 inch subwoofers | Need a custom build? Contact us

Amplifiers for the System

Power for Your Subwoofer System

Monoblock amplifiers matched to the power requirements of the drivers these enclosures are built for. Buy the enclosure, match the driver, pick the right amplifier.

Rainbow Audio Dream 0.5K Mono Class D Amplifier

Rainbow

Rainbow Audio Dream 0.5K Mono Class D Amplifier

$ 89.99 $ 399.99
Rainbow Audio SL-M2 2 channel micro amplifier

Rainbow

Rainbow Audio SL-M2 2 channel micro amplifier

$ 98.99 $ 549.99
US Acoustics Lisa 4 Channel Class AB Amplifier 4 x 50w US Acoustics

US Acoustics

US Acoustics Lisa | 4 Channel Class AB Amplifier | 4 x 50w

$ 159.99
US Acoustics Wendy 2 Channel Class AB Amplifier 2 x 75w US Acoustics

US Acoustics

US Acoustics Wendy | 2 Channel Class AB Amplifier | 2 x 75w

$ 159.99

View all car amplifiers | Need a custom build? Contact us

Last updated August 30, 2026