Performance Optimized Down Fire Wide Sealed Dual 10" Shallow Sub Enclosure | Prodigy NB3-10

The Down Fire Wide Format

Down Fire Wide answers a specific space problem. The floor under the rear seat of a truck or SUV, and many narrow cargo floors, is long and shallow, and a standard 30 by 15 inch enclosure will not go in it.

So the cabinet is turned sideways. This one runs 41 inches wide by 12 inches deep by 5.9375 inches tall, measured in the down fire position. Against our standard 30 by 15 inch dual NB3 cabinet it takes the same pair of NB3-10D4 drivers, sits 3 inches shallower front to back and runs 11 inches longer. The airspace lost from the 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 the Prodigy NB3-10D4

Both baffle positions are bored to the NB3's 9 3/16 inch cutout, and the cabinet height starts from its 3.00 inch mounting depth.

The NB3-10D4 is a dual 4 ohm driver rated 600 watts RMS and 1200 watts peak, with 11mm of one-way Xmax at 70% BL. The motor is a 70 ounce ferrite magnet with a 2.5 inch high-temp four-layer copper voice coil on a black aluminum former, rated to 500 degrees Fahrenheit, and an FEA designed center pole vent pulls heat out of the coil gap.

The spider is a cotton and Nomex blend with stitched flat tinsel leads, which is the detail that stops the ticking unstitched leads develop at high excursion over time. Treated paper cone, rubber surround, stamped steel frame. Moving mass is 151.63 grams against a BL of 23.365, so Prodigy built this to control the cone rather than only to fit under a seat.

Across the pair that is 1200 watts RMS combined. The 3.00 inch mounting depth is the whole reason the NB3 exists. Prodigy built it for under and behind truck seats, which is exactly where a 12 inch deep cabinet goes. The frame is round and sits on the 12 inch deep baffle with material to spare fore and aft.

Net Volume and Alignment

Each chamber holds 0.323 cubic feet net, 0.646 total, from 0.863 cubic feet gross after 0.10 cubic feet of driver displacement, published by Prodigy per driver.

Computed from the driver's published Thiele-Small parameters, that produces Qtc 0.653 with Fc at 58.5 Hz and a predicted F3 of 63.6 Hz per driver.

Height is the free dimension. With the footprint fixed at 41 by 12, the cabinet height was solved to put each chamber on the same airspace as the standard 30 by 15 box, then rounded up to the next sixteenth so the volume lands on the target rather than under it. The motor clears the top panel with 2.19 inches to spare, so airspace set this height, not clearance.

That is a deliberately small chamber for this driver. The NB3-10D4 has a Qts of 0.407 and a small 14.43 litre Vas, and drivers with those numbers run overdamped in generous enclosures. The smaller chamber moves each driver toward the 0.707 reference rather than away from it, and it is why this dual can stand only 5.9375 inches tall. Prodigy publishes a larger sealed range; it reads like a prefab truck box target where cabin gain carries the bottom end.

The stiff air spring raises Fc to 58.5 Hz and mechanically limits excursion at the very bottom. That protects the driver, and it means the deepest material leans on cabin gain rather than cone travel, which is the right trade in a truck cab.

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. Each NB3-10D4 gets its own 0.323 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.

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 5.9375 inches tall, measured in the down fire position. The 1.75 inch feet ship with the enclosure but are not installed, so plan the space around an installed height of 7.6875 inches if you use them.

Power and Wiring

Prodigy rates the NB3-10D4 at 600 watts RMS continuous and 1200 watts peak, 1200 watts RMS combined across the pair. Target 450 to 600 watts per driver.

One side mounted terminal cup serves both chambers, pre-wired in 12 gauge OFC to both driver positions in parallel, so you do not run the chambers separately to the amplifier. Each driver is dual 4 ohm, so final impedance is set at the drivers. Wire both identically, since mismatched wiring between chambers will split power unevenly, and confirm the resulting load against your amplifier's minimum stable impedance before powering the system.

Bring your own pair of Prodigy NB3-10D4 subwoofers. The enclosure carries a 1 year limited warranty. Plush black carpet.