Performance Optimized Down Fire Sealed 12" Enclosure | Hertz Mille Pro MP 300 Single 12" Sealed enclosure

Because the driver's mounting depth sets the minimum cabinet height. The MP 300 mounts 6.46 inches deep. Our double baffle recovers 0.75 inches since the outer layer is a flush recess and the driver bolts to the inner layer, and a 3/8 inch milled relief behind the magnet recovers a little more. With half an inch of clearance behind the motor the minimum internal height is 5.875 inches, which works out to 1.10 cubic feet net.

The extra volume helps. Hertz publishes Qtc 0.82 at their 28 liter figure. At the 31 liters this cabinet provides, the system lands at Qtc 0.771 with F3 at 40.7 Hz. Better damped with a gentler corner and no meaningful loss anywhere.

Because sensitivity determines how much output you get per watt. Most subwoofers in this category sit in the low to mid 80s, and high-excursion shallow drivers frequently drop to 81 or 82 dB as a tradeoff for their motor design. At 86 dB the MP 300 is among the most efficient drivers in the Proline X Down Fire line.

In practical terms a 4 dB sensitivity advantage means roughly two and a half times the acoustic output from the same amplifier power. You can reach your target output on a smaller amplifier, or reach it with headroom to spare on a large one, which reduces thermal stress on the driver over long listening sessions.

No, and the reason is worth explaining. The MP 300 has 74 liters of Vas and wants close to a cubic foot of net airspace per driver for a good alignment. In a dual chamber cabinet the footprint is split in half, so all of that volume has to come from height instead.

Running the numbers, a dual MP 300 down fire enclosure would need to stand over 11 inches tall to reach even 0.80 cubic feet per chamber, and building it shorter pushes Qtc past 1.0 which produces a peaky, poorly controlled alignment. Two single enclosures deliver better sound in a more usable form factor. Drivers with a smaller Vas, like the Mille Pro MPS series, work well as duals in this format.

The enclosure has one side-mounted Proline X terminal cup pre-wired in 12 gauge OFC. Final impedance is set at the driver, and it depends on which version you buy.

The MP 300 D2.3 has dual 2-ohm coils: parallel gives 1 ohm, series gives 4 ohms. The MP 300 D4.3 has dual 4-ohm coils: parallel gives 2 ohms, series gives 8. Hertz rates the driver at 600 watts RMS. Confirm your amplifier is stable at your chosen load before powering the system.

The 12 is more efficient and has more cone area; the 10 has a slightly lower F3 in its cabinet. The MP 300 measures 86 dB sensitivity against the MP 250's 83.4, which is a substantial real-world difference, and it has a lower free-air resonance at 24 Hz against 30 Hz.

In their respective enclosures the 10 reaches F3 39.4 Hz at Qtc 0.741 and the 12 reaches 40.7 Hz at Qtc 0.771, so the 10 edges it on paper. But the 12 moves far more air and gets louder on less power. Both share the same 600 watt rating and 17mm of excursion. Cabinet heights are 7.4375 inches for the 10 and 8.125 for the 12.

Side mounted. Every Proline X Performance Optimized enclosure uses a side mounted terminal cup regardless of alignment, whether standard, wedge, or down fire. On this cabinet that keeps the connection fully accessible with the enclosure in its installed position, since the baffle faces the floor. The cup is our Proline X ABS and carbon fiber composite unit, recessed, with stainless hardware, copper ring terminals, and pre-wired 12 gauge OFC.

V-groove and dado joinery, CNC-cut on ShopSabre routers from Langboard Elite MDF. Every panel joint is a machined interlocking groove that mechanically locks the panels before adhesive is applied, which is what keeps the cabinet airtight under sustained pressure cycling.

The front baffle is a double layer at 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 and matters with an 11.30 inch cutout. A 3/8 inch relief is milled into the opposite panel behind the magnet. Perimeter cross-bracing and pre-installed polyfill complete the build. Assembled and inspected in Tullahoma, Tennessee.

No. This listing is for the enclosure only. Bring your own Hertz Mille Pro MP 300 D2.3 or MP 300 D4.3. The cutout, mounting depth and magnet clearance are all cut specifically for this driver.