20hz Ported vs Sealed Box Subwoofer Enclosure Bass Test No Subsonic Filter Used - YouTube
Acoustech Elite Series PL-300 – 1400W 12” Powered Subwoofer with Tri-Tuned Ports and “BASS BOOST” Feature for Room Shaking Bass Down to 15Hz – BIC America
Digger8 Sub - diggity dig it all the way to 20Hz - Techtalk Speaker Building, Audio, Video Discussion Forum