WinISD SPL plots for sealed 12NMB420 F3~140Hz and 12NLW9300 F3 ~120Hz easy crossover to most woofers. Note higher SPL/watt with 12NMB420.
For their BMF-1 speaker, Tweek Geeks published several construction photos. Run an extensive Google search.
The BMF‐1 stands 43”high x 16”wide x 20”deep, and this depth is needed for ~4cuft of volume for the two 12" woofers.
34 best Tweek Geek's BMF Speaker in the making images on Pinterest | Geek, The o'jays and Speakers
1) Review info on Linkwitz Transform bass extension technology and circuits/filters. Also DSP equalization like from MiniDSP.
2) Using sealed woofers is becoming popular because they have excellent transient response, and they simplify modern DSP room equalization. Several plate amps include a Linkwitz bass transform circuit, or a few equalization controls.
3) With bass equalization circuits from DSP or Linkwitz Transform circuits, you can get deep bass with 12" woofers or larger 18" woofers. The BMF-1 uses two 12" woofers with equalization and 400 watt amplifiers. Using 18" woofers will need significantly lower power, at the cost of a 22" deep cabinet. Since most speakers are placed about 2 feet away from the rear wall to controll short delay wall reflections, deeper cabinets are mainly an esthetic issue. My design sketch is 18"wide x 46"high x 22"deep which produces ~6cuft of woofer volume. The center for the XT1086 is 39" above ground, an ideal ear level, and ideal height to keep enough wood above the XT1086 for smoothing the 1600Hz = 8.5" wavelength baffle reflection.
4) The 18LW1400 models well for equalized deep bass, but requires more power than the Faital 18FH500. The 18LW1400 looks like a very good woofer choice with a solid state amp. The 18LW1400 is 8.5" deep, so two side-side woofers require a 19" wide cabinet for a perfect fit.
