Audio Reviews

Hertz Mille Pro Shallow (MPS) Subwoofer Detailed function test

In this article: We will provide an in-depth overview of the Hertz Mille Pro subwoofers and the key features that we believe are important for those interested in purchasing and installing a Hertz MPS subwoofer.

Functional overview Hertz Mille Pro Shallow Subwoofer

Hertz products have been on our list of the best car subwoofers and best car speakers for almost a decade. We’ve been installing Hertz products since the late 2000’s and have watched them become a mainstream high end lineup in the US. The Mille Pro subwoofers are another example of why we’ve been fans of Hertz for so long!

The Hertz Mille Pro Series range includes coaxial and component speakers and a range of subwoofers to provide a complete in-car entertainment system. The newest model in the lineup is the Mille Pro Shallow or MPS. The Hertz MPS subwoofers are designed from the ground up to take advantage of numerous technologies to enhance the bass in your car while maintaining a compact package that is ideal for use under the back seats of trucks or anywhere the space is tight. Hertz MPS subwoofers are available in 10″ and 12″ designs and offer either two ohm or four ohm resistance ratings to optimize your system.

Compact design features

One of the main reasons consumers would choose the MPS subwoofers for their system is obviously the incredibly compact design, which allows the subwoofer to be installed in very tight spaces. The new 10″ MPS design measures just 3 1/4″ deep when assembled compared to 5 9/16″ required for the concurrent Mille Pro subwoofer design. That matches JL Audio’s 10TW3 in terms of depth, which has always been one of our favorites for super-compact subwoofers.

Most flat mount subwoofers are a compromise between power and space, often with predictably disappointing results. This is not the case with the MPS. Hertz claims the design offers 20 percent more cone excursion capacity compared to the MP subwoofer. A special suspension design helps the subwoofer achieve excellent results while remaining relatively flat compared to other subwoofers.

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Hertz calls the technology “Smart Suspension Group Design,” which moves the magnet group up and allows the subwoofer to perform like a traditional full-depth subwoofer.

Charge air cooling revolution

Hertz Air intercooler Revolution AIR

Air Intercooling Revolution (AIR) technology provides a path for airflow to prevent internal air compression while maintaining maximum cooling airflow to the magnet and motor structure. The AIR design creates ideal fluid dynamics in the inner acoustic structure for maximum resilience. This design keeps the subwoofer in a thermally stable temperature range to enhance bass output.

Six-layer voice coils

Hertz MPS 6-layer voice coil

Voice coils that use more layers are said to reduce overheating by providing a larger surface area that allows for more space for heat absorption. The downside of a multi-layer voice coil is the reduction in frequency response above 500Hz, which isn’t a problem for these subwoofers as they’re not designed for mid-range performance.

The MPS Series subwoofers use single voice coils in 2 ohm and 4 ohm variants. The single design helps reduce the overall size of the subwoofer. The standard MP subwoofers are available with dual voice coils.

Modeling with the finite element method (FEM).

The magnet assembly was modeled using the finite element method, which allows Hertz’ sound engineers to customize the sound using dozens of complex calculations to ensure proper sound production even at high power ratios.

The pole piece has also been fully modeled to produce a design that improves unity power factor, thereby improving overall sound quality and balance across the full range of subwoofer capabilities. By focusing on cutting-edge modeling techniques, Hertz engineers have built a compact subwoofer that packs a punch well beyond its size.

Developed for compact boxes

The MPS subwoofers feature a woofer cone and spider design that has been extensively tested by Hertz’s R&D engineers to ensure the assembly performs perfectly within the confines of a compact, sealed enclosure. The design allows these speakers to be mounted in places almost no other subwoofer fits and still sound like a proper full-size subwoofer.

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Hertz compact sealed boxes

Not only have these subwoofers been modeled and engineered to ensure optimal performance in a sealed enclosure, but Hertz also builds its own sealed designs to provide up or down performance. The boxes feature special internal baffle and support structures that prevent resonance and distortion while maximizing the volume of the subwoofer. The boxes offer rounded corners to make installation easier too.

Woofer Cone, Spider and Surround

The MPS subwoofer’s low-frequency cone is constructed from layers of compressed paper that have been mineral-injected into it to create a strong, lightweight structure that provides enough damping to avoid resonance and ensure precise, tight bass even at high power.

The spider’s unique design allows the woofer cone to move more than other subwoofers of a similar size, producing deeper and fuller bass while keeping depth compact. The design sits higher on the magnet structure than other designs, allowing the cone to stay centered no matter how much power is applied.

The surround is a rubber foam construction that is durable but also soft enough to allow the MPS subwoofers above-average excursion rates.

We thought this was a cool feature that few manufacturers make with their speakers and subwoofers these days. The MPS subwoofers provide eID information that allows you to track the build of your speaker throughout its construction. You’ll see the results of each step of the process, including testing the speaker to ensure it performs as it should when it leaves the factory. Every MPS subwoofer has a QR code that you can scan to learn all about your speaker.

main features

  • Ultra shallow overall depth
  • Available in 10″ and 12″ sizes with options for 2 or 4 ohm resistance
  • Optimized for extremely compact closed housing 12-14L (0.4-0.5CF)
  • Air Intercooling Revolution (AIR) eliminates air compression related limitations
  • Unsurpassed mechanical deflection, +20% over traditional designs
  • Six-layer copper voice coil (38mm/1.5in) ensures high thermal capacity
  • The non-ventilated back allows for a reduced case depth
  • Robust screwless mesh grille including black screws
  • Die-cast aluminum frame
  • Solid horizontal 8AWG spring terminals
  • EID: Scan, Discover, Identify
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Frequently Asked Questions (FAQs)

Will the MPS perform as well as the MP with the same amp?

Designed to operate in a compact package, the MPS uses special features to maximize excursion so you get deep, hard-hitting bass from the subwoofer that rivals that of a full-size MP subwoofer.

What is the difference between two ohm and four ohm options?

Subwoofers with 2 ohm resistance produce slightly more punchy bass and are typically louder than the 4 ohm version. Four-ohm versions produce deeper, clearer-sounding bass. You should also use 2 ohm speakers in series when connecting them to a 4 ohm amplifier.

Will this subwoofer work in a ported or free air setup?

The MPS subwoofers are designed for sealed boxes and will work with many ported box designs. These subwoofers require the ability to use the air in a cabinet for bass response, so they are not intended for outdoor systems.

Can this subwoofer be bottom mounted?

Yes, the Mille Pro Shallow Subwoofer can be bottom mounted. The subwoofer depth increases to just over four inches when floor mounted.


The Hertz Mille Pro Shallow continues the tradition of the Hertz Mille Pro line, using proprietary technology and extensive modeling to ensure the strongest and most punchy bass frequencies while maintaining high sound quality. Until now we’ve relied heavily on JL Audio’s TW3 and TW5 designs for ultra-thin subwoofers like this one, but the MPS series is a serious contender for the legendary TW3 subwoofer design. The Mille Pro Shallow is an ideal choice for mounting under the seat of a pickup truck or in the trunk of smaller cars without taking up all the space. We’ve had good success with the Mille Pro subwoofers and believe the new MPS design will become one of the most popular subwoofer designs to mount in locations where an ultra-compact enclosure is required.

Joshua Elliott
Bacon practitioner. Certified coffee fan. Lifelong food junkie. Web trailblazer. Typical internet fanatic.

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