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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.