Hertz MPBX 300 S2 Review: A 12-Inch Sealed Box for Low, Tight Spaces
Updated: Oct 7
The Hertz MPBX 300 S2 is a ready-made, ultra-shallow sealed box from Hertz's Mille Pro range, loaded with the 12-inch MPS 300 S2 driver and rated at 500 W continuous (1,000 W peak) into 2 ohms, with 84.5 dB sensitivity. The whole box is 175 mm tall on a 607 x 401 mm footprint. Its Indian MRP is ₹59,990, ₹10,000 above the bare MPS 300 driver. It is the 12-inch partner to the MPBX 250 S2, for owners who want proper bass without losing the boot. See today's price on our Hertz MPBX 300 S2 product page.
Quick summary
A finished sealed box: the 12-inch, 2-ohm MPS 300 S2 in a braced, damped 15 mm wooden enclosure, with grille and plug-in terminal.
Hertz pitches it for spaces where height is limited, such as under a pickup's rear bench, and it can fire up or down.
It needs a mono amplifier stable at 2 ohms; about 500 W RMS matches its rating.
Owners on a UK retailer's page rate it highly in short reviews; we found no professional test.
Hertz MPBX 300 S2 specifications
Specification | Hertz MPBX 300 S2 |
|---|---|
Type | Loaded ultra-shallow sealed enclosure |
Driver | MPS 300 S2, 300 mm (12-inch), single voice coil |
Impedance | 2 Ω |
Power handling | 500 W continuous / 1,000 W peak |
Sensitivity | 84.5 dB |
Frequency response | 25–400 Hz |
Voice coil | 38 mm (1.5 in), six-layer copper |
Xmax / Xmech | 16.8 mm / 20 mm |
Fs / Qts / Vas | 24 Hz / 0.51 / 64.9 litres |
Enclosure | Sealed, 15 mm wood, internal bracing and damping |
Dimensions (A x B x C) | 607 x 401 x 175 mm (C1: 133 mm) |
Terminals | SSP plug-and-play block plus push terminals |
Grille | Screw-less mesh, included |
India MRP | ₹59,990 |
Figures come from Hertz's MPBX 300 S2 page and our Indian listing. Hertz doesn't publish the box's internal volume or weight there.
What you get: the driver, the box and the plug
The driver is the Hertz MPS 300 in its 2-ohm form: a 38 mm six-layer copper coil with 16.8 mm of Xmax, in a driver only 88 to 89 mm deep (Hertz's documents differ by a millimetre). Hertz credits a support structure that lets the magnet sit further inward, and says its A.I.R. design prevents air-compression limits. The cone travels a long way without a deep basket, which keeps the box low.
The box uses 15 mm wood with panel-to-panel bracing and solid corners, plus internal sound-absorbing material that, Hertz says, makes it behave as if it were larger. Wiring goes through the SSP (Sub Smart Plug), a plug-and-play terminal block alongside push terminals, which should make the box quick to disconnect when you need the whole boot. The screw-less grille's logo can be turned for reverse mounting.
Up-firing or down-firing: the 2S² design
Hertz calls it 2S², for two sides and two sounds. On its supplied feet, which have hook-and-loop inserts, the box fires down, and Hertz says this increases low-frequency extension. Flipped to fire upward, it gives more punch and definition. Hertz lists two heights, 175 mm and 133 mm, which Four Car Audio's listing explains as with and without the feet. Try both orientations before fixing the box.
Amplifier pairing and wiring
The single 2-ohm voice coil means a fixed 2-ohm load, so you need a mono amplifier that is stable at 2 ohms. Hertz's DP 1.500 is the natural match: 500 W RMS into 2 ohms at 14.4 V and 1% distortion, exactly the box's continuous rating, with an optional HRC 02 remote for bass level. It uses a single 30 A fuse, and Hertz's 21 A consumption figure is for maximum musical power, not a ceiling, so size the power cable and battery fuse to suit.
Hertz's four-channel DP amps won't do it bridged: the DP 4.300 and DP 4.400 are rated for 4 ohms minimum in that mode. At 84.5 dB the box also wants real power; Hertz lists the full-depth MP 300 at 86 dB. For the same driver in a sealed box, Hertz suggests a 70–80 Hz low-pass and a 15 Hz subsonic filter at 24 dB per octave, a sensible starting point. Our guide on why a car system needs an amplifier covers the basics.
What owners and reviewers say about the Hertz MPBX 300 S2
We found no professional review. This is the owner feedback we found when we checked in October 2026.
UK retailer Four Car Audio shows five ratings, with an overall score at the top of its scale. Four dated reviews are visible, from March 2024 to July 2026: three at the top mark and one a step below. The newest reports a huge improvement in bass and sound quality, but says it's too early for a full verdict while the sub wears in over about a month. Others call the sound amazing and rate it above all their earlier equipment.
None of the visible reviews mentions the car or amplifier, so treat them as a positive signal, not a test. If you run one, tell us how it performs.
MPBX 300 S2 vs MPS 300, MPBX 250 S2 and CBA 250
The bare MPS 300 (₹49,990 MRP) is the same driver, also sold as a 4-ohm S4. It saves ₹10,000, but you need a box: Hertz's sealed design is 22.7 litres, built 510 x 406 x 160 mm or as a lower but much wider 770 x 406 x 115 mm version. The MPBX arrives finished.
The MPBX 250 S2 has the same ₹59,990 MRP in a smaller 531 x 361 x 160 mm box. Its MPS 250 S2 driver is rated at 82.5 dB against 84.5 dB here, so if the 12-inch box fits, it should play louder on the same amplifier.
The Cento CBA 250 (₹49,990 MRP) is a no-amplifier alternative: a 158 mm tall active 10-inch box with its own 250 W amplifier, a high-level input and a remote. It shares the 2S² design and SSP plug, so those aren't reasons to choose the MPBX; double the power handling and a bigger cone are.
Who should buy it, and who shouldn't
Buy the MPBX 300 S2 if you want 12-inch bass and a usable boot, your space is limited in height, and you have or plan a 2-ohm-stable mono amplifier of around 500 W.
Look elsewhere if you have room for a conventional box: the MP 300 has a lower MRP (₹39,990), 600 W continuous and 86 dB, though its 450 x 360 x 280 mm sealed box is 105 mm taller. Choose the CBA 250 if you don't want a separate amplifier, or an MPS 300 S4 in a custom box if your amplifier needs 4 ohms.
Installation notes for Indian cars
Measure the floor, not just the height: the box needs 607 x 401 mm, and in a sedan it has to clear the boot hinges and any CNG cylinder. The hook-and-loop feet should help it grip the carpet, but a 12-inch box still needs straps or brackets for speed breakers and broken roads.
Mount the amplifier where air reaches it, not under luggage, because a closed boot gets very hot in summer. Use a fused power cable from the battery, and check the charging system if you often idle in traffic with the AC on. Our sound damping guide helps if you're treating the boot too. VA3 Car Studio in Ghaziabad offers professional installation and can check fitment for your car.
Price and where to buy
The Hertz MPBX 300 S2 has an MRP of ₹59,990 in our current Indian listing. Check today's price and availability on the MPBX 300 S2 product page, and ask us to check fitment first. Every box we sell is a genuine Hertz product.
The bottom line
This is a tidy answer to a common problem: 12-inch bass without giving up the boot. The ₹10,000 premium over the bare driver buys a finished, braced box that fires up or down. It needs a strong 2-ohm mono amplifier, and the owner feedback is positive but thin. If the footprint fits, it's an easy way into Mille Pro bass.
Hertz MPBX 300 S2 FAQ
Does the Hertz MPBX 300 S2 need an amplifier?
Yes. It is a passive box with a 2-ohm driver, so it needs a mono amplifier that is stable at 2 ohms. Around 500 W RMS matches its continuous rating, and Hertz's DP 1.500 makes exactly that into 2 ohms.
Can the MPBX 300 S2 be wired to 4 ohms?
No. The MPS 300 S2 inside has a single 2-ohm voice coil, so the load is fixed. If your amplifier needs 4 ohms, buy the bare MPS 300 in its S4 version and use a custom sealed box.
Should the box fire up or down?
Hertz says down-firing on the supplied feet increases low-frequency extension, while up-firing gives more punch and definition. Try both in your car before fixing the box in place, then secure it properly.
Buy the Hertz MPBX 300 S2 Mille Pro in India
Check the Hertz MPBX 300 S2 Mille Pro price in India, browse more Hertz subwoofers or compare all enclosed and powered subwoofers in India. Want it fitted properly? Book subwoofer installation at our Ghaziabad studio.
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