Mobile Electronics› Video Accessories

Rockford Fosgate

Prime R1 8-Inch Marine Subwoofer

$129.99

SKU: RM18D4B

In Stock
In Stock
Ships by Sep 9
Free Shipping over $200
$100 Minimum Order
30 Days Return
INSTALL DIFFICULTY
DIY PRO SHOP

Moderate — 2–4 hours

Overview

The Rockford Fosgate RM18D4B is an 8-inch Prime R1 subwoofer designed for marine, watercraft, or powersports applications. It features a color-matched grille and is built to be UV and moisture resistant. This subwoofer can be installed in sealed, vented, or infinite baffle enclosures.
Show original supplier description
The Rockford Fosgate RM18D4B is an 8-inch Prime R1 subwoofer engineered for demanding environments, making it ideal for marine watercraft and powersports applications. Its construction includes a 100% UV-stable ASA injection-molded plastic frame, UV and salt-fog resistant Santoprene surround, and a moisture, tear, and fatigue-resistant Aramid fiber spider. The injection-molded mineral-filled polypropylene cone body is also treated with UV inhibitors. It offers a power handling of 150 Watts RMS and 300 Watts Max, with a dual 4-Ohm nominal impedance and a 1.5-inch aluminum voice coil. The speaker is equipped with proprietary corrosion-resistant spring-loaded push terminals and an ultra-flexible, fully insulated silicone lead wire for reliable connections. Installation flexibility is supported by its ability to be used in sealed, vented, or infinite baffle enclosures. Additional features include a removable trim ring/grille and a mounting depth of 3.6 inches with a 7-inch cutout diameter. This model is noted as being discontinued, potentially replaced by the M1D4-8B. It comes with a 2-year warranty.

Product descriptions are provided by our supplier partners and may not always be perfectly accurate. Not sure this fits? or call (760) 282-4645 and we’ll verify before you order.

Fitment

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Specifications

BrandRockford Fosgate
Part NumberRM18D4B
CategoryMobile Electronics

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Returns & Fitment

Built for enthusiasts. Every order is backed by our 30 day return window on eligible items. Unused and uninstalled products may be returned with approved RMA and no restocking fees when received in new condition. Orders placed through the MOTORMIA app with a complete build qualify for our Fitment Guarantee — free return shipping if the part doesn’t fit your exact setup. The guarantee covers fit only; installation must follow manufacturer instructions, and we recommend a qualified shop for parts marked Difficulty 4–5.

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Shipping

Orders are processed in 1–3 business days. In stock parts ship promptly from our partner network. Special-order items either aren’t currently stocked or are built to your spec — expect 4–6 weeks. If a part goes on backorder while your order is in the queue, we’ll reach out and work through discounted alternatives together.

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