Rockford Fosgate M212S4

12" 4-ohm marine subwoofer

  • Rockford Fosgate M212S4


  • Rockford Fosgate M212S4


  • Rockford Fosgate M212S4

  • Rockford Fosgate M212S4

  • Rockford Fosgate M212S4

  • Rockford Fosgate M212S4


Our take on the Rockford Fosgate M212S4

by Ken Nail
Rockford Fosgate

You expect performance and aggressive styling from Rockford Fosgate, and you get both with the M212S4 marine subwoofer. It delivers classic Rockford Fosgate bass that'll liven up the party on your barge, while the cool stainless-steel grille tells your crew that you're serious about your sound. This 12" sub is built with parts designed specifically for marine performance, so you can count on it to stand up the effects of moisture, salt air, and UV rays.

Rockford Fosgate M212S4

You can install the M212S4 in a sealed or ported box, or mount it in a bulkhead or other free air application.

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  • 12" 4-ohm marine subwoofer
  • injection-molded mineral-filled parabolic polypropylene cone with TPE surround
  • aramid-fiber spider
  • UV-stable Centrex® injection-molded plastic parts
  • gold-plated corrosion-resistant terminals
  • suitable for free-air installations
  • power handling up to 300 watts RMS
  • peak power handling: 600 watts
  • frequency response: 30-250 Hz
  • sensitivity: 87 dB
  • top-mount depth: 6-5/8"
  • sealed box volume: 1 cu. ft.
  • ported box volume: 1.5 cu. ft.
  • warranty: 1 year
  • Our 60-day money-back guarantee

Hands-on research from the Crutchfield Labs (what are the Labs?)

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What's in the box?

Download owner's manual

  • 12" Marine subwoofer
  • White polymer and stainless steel grille
  • Four 2-3/8" Stainless-steel Allen head screws
  • Four 1-1/4" Stainless-steel Allen head screws
  • 4mm Allen head bit
  • Owner's manual (English/ French/ Spanish/ German)

Our Product Research Team

At Crutchfield, you'll get detailed, accurate information that's hard to find elsewhere. That's because we have our own in-house Product Research team — they open the box, verify contents, check the owner's manual, and record dimensions, features and specs. We stay on top of new products and technologies to help people make informed choices.


Marine Tested: Rockford Fosgate's M212S4 marine subwoofer is subjected to ASTM B117 and ASTM D4329 test standards to ensure it can withstand the corrosive effects of salt/fog, as well as sunlight, moisture, and heat.

Woofer: The subwoofer features an injection-molded, mineral filled parabolic polypropylene cone with UV inhibitors. The TPE (Thermo-Plastic Elastomer) surround is also UV and salt/fog resistant.

Centrex Basket: The basket and other plastic parts are made of UV stable Centrex injection molded plastic.

Magnetic Shielding: The motor structure is magnetically shielded to reduce the potential for electromagnetic interference.

Compression Terminals: The M212S4 features spring terminals which accommodate pin connectors, single banana plugs, dual banana plugs (standard 3/4" width) or bare speaker wire up to 10 gauge.

VAST Surround: The Vertical Attach Surround Technique (VAST) increases a speaker's effective radiating cone area without increasing the size of the basket.

FlexFit Basket: The Flex Fit frame utilizes slots (where possible) instead of single screw sized holes; allowing slight adjustment of the speaker when mounted.

Mounting Hardware: Marine-grade stainless-steel mounting screws are included.

Enclosure: The M212S4 can be mounted in a sealed or ported box, or in an infinite-baffle (free-air) application. The optimum internal volume of a sealed enclosure is 1.0 cubic foot (from 0.7 to 1.80 cubic feet is acceptable). The 1.0 cubic foot enclosure yields a -3dB point of 53.7 Hz. The best ported enclosure volume is 1.5 cubic feet using one 3" diameter x 5.74" long port; this yields a tuning frequency of 40 Hz and a -3dB point of 37.2 Hz.

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For a more in-depth review and enhanced detailed information on the Rockford Fosgate M212S4, please visit the Crutchfield website product page (/ISEO-rccbcspd/p_575M212S4/Rockford-Fosgate-M212S4.html ).

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