SELENIUM 18SWS800 High-Power Professional Subwoofer 4" diameter, 4-layer voice coil wound on a fiberglass former on-pressed long fiber pulp cone has the necessary stiffness for a linear response The SWS800 high-power professional subwoofers were specially designed to reproduce sound at the very low end of the audio spectrum. Triple cooling system directly cools the gap and the air trapped between the two spiders Highly reinforced cast aluminum frame 4" diameter, 4-layer voice coil wound on a fiberglass formerNon-pressed long fiber pulp cone has the necessary stiffness for a linear response Bumped and undercut T-yoke assures maximum displacement Triple cooling system directly cools the gap and the air trapped between the two spidersHighly reinforced cast aluminum frame