Hertz MPS 300 S4 12" Subwoofer: Who Should Buy It?
By Car Audio and Tint | Car Toys | Washington, Texas, Colorado ... | Published: 2026-11-01
Category: Product Reviews
A practical buying guide to the Hertz MPS 300 S4 12" subwoofer. Learn who it suits, who should look elsewhere, and how to decide if it fits your build.
Quick answer
The Hertz MPS 300 S4 is for drivers who need a 12-inch subwoofer that works in very small sealed enclosures, especially under a truck bench or in a tight cargo area. If you have room for a standard-depth box or want a high-output ported setup, other subs make more sense.
Why shallow mounting depth changes the decision
The MPS 300 S4 is a shallow-mount subwoofer, which means it can fit in spaces where a conventional 12-inch sub won't. That matters most in pickup trucks, hatchbacks, and small SUVs where the enclosure height or depth is limited. The trade-off is that shallow subs often give up some excursion and output compared with full-depth designs, so you need to match it with an amplifier and enclosure that play to its strengths.
Sealed box requirements: small is the point
Hertz optimizes this sub for ultra-compact sealed boxes starting at about 22.7 liters (0.8 cubic feet). That is unusually small for a 12-inch sub, and it is the main reason to choose this model. If you were planning a large sealed box or a ported enclosure, you are paying for a feature you won't use. Stick with a sub designed for that application instead.
Power and system matching
The catalog does not list power handling, sensitivity, or impedance for the MPS 300 S4, so you should confirm those specs with the retailer or Hertz before buying an amplifier. As a general rule, shallow subs benefit from an amplifier that can deliver clean power without forcing the driver to over-excursion. If you already own a high-power amp, check that the sub's rated power is a good match rather than assuming it will handle the same power as a standard-depth sub.
Decision rules for the Hertz MPS 300 S4
- Measure your available enclosure space first: If your maximum box volume is around 0.8 cubic feet and you need a 12-inch sub, the MPS 300 S4 is one of the few options that will work. If you have room for 1.25 cubic feet or more, a standard-depth sub usually gives you more output per dollar. Space is the deciding factor, not brand loyalty.
- Choose sealed, not ported: This sub is optimized for sealed enclosures. If you want a ported box for maximum output, pick a sub designed for ported applications instead. Don't force a shallow sub into a ported design.
- Verify amplifier power before you buy: Because the catalog doesn't list power handling, check the sub's RMS rating and match it to an amplifier that can deliver that power cleanly. Overpowering a shallow sub is a common way to damage it. A modest, clean amplifier is safer than a big one turned down.
Product facts
- Hertz MPS 300 S4 Mille Series 12" Subwoofer: The Hertz MPS 300 S4 is a shallow 12-inch subwoofer designed for ultra-compact sealed boxes starting at 22.7 liters (0.8 cubic feet). This makes it a strong candidate for under-seat truck boxes and other tight installs where a standard sub won't fit.
Hertz MPS 300 S4 Mille Series 12" Subwoofer
Who should buy it?
Best for
- Pickup truck owners who need a sub under the rear bench
- Drivers with very limited cargo space who still want a 12-inch sub
- Builders who want a simple, small sealed enclosure
Not for
- Listeners who want maximum output and have room for a larger box
- Anyone planning a ported enclosure
- Buyers who need published power specs before choosing an amplifier
