My goal is to build a great subwoofer using one channel of my Parasound 1500A amp, which provides 315W at 4ohm. The Tumult and AV15 aren’t readily available, and seem to like more power. The Tempest is a forum favorite, but I think the Maelstrom may actually work better as you’ll see in this analysis using WinISD 0.50a6. The maelstrom is now $225 from Adire, and there is at least one example: http://www.acoustic-visions.com/maelstromsubpics.htm You can read the Adire vented white papers at http://www.adireaudio.com/Files/Vent...plications.PDF You may also want to read the two recent threads on maelstroms, which don’t have any results posted. My primary goal is sound quality. I will be moving into an apartment soon, so do not know the exact room dimensions (likely under 15x20 with several openings). I also shouldn’t upset the neighbors too much. I will probably use the system 70/30 music/movies. I will be using aura bass shakers in the couch, which may help the low bass feeling. My main speakers are -3dB at 28Hz, so for a lot of 2 channel music I may not even use the subwoofer (unless it sounds better than the Lsi15’s ported 8”). My HK525 has flexible triple crossover bass management, so after the sub is built I can explore this. I will be using a BFD to flatten response on the sub and shakers. Sonotubes are too weird looking to pass the WAF but gigantic boxes are ok. All graphs are plotted with 315 watts at 2.5 meters (estimated seating position). The plotted designs are: Tempest (blue) Sealed Q= .707 Butterworth 122 Liters Tempest (green) Sealed Q= .577 Bessel 230 Liters Tempest (black) Vented: EBS alignment 340 Liters tuned to 15.8Hz Maelstrom (red) Sealed Q= .577 Bessel 150 Liters Maelstrom (orange) Vented: EBS 320 Liters tuned to 20Hz Maelstrom (purple) Vented: custom design 280 Liters tuned to 17Hz Maelstrom (light green) Vented: custom design 340 Liters tuned to 17Hz Note that even though the Maelstrom driver is larger than the Tempest (18 vs 15”), the comparable Maelstrom designs aren’t always larger. Because of the design criteria mentioned, I’m guessing that EBS and Bessel designs will be best for tight “audiophile” sound.