I want my Avalanche 18 to go flat to 15hz

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I've got one Ascendant Audio Avalanche 18 and have decided it'd be put to better use in a Home Theater environment.

I'd like it to extend 15-50/60hz and reach reference levels >110dB.

I can fit virtually any enclosure (8' sonotube with a diameter of 30-36" isnt out of the question, >45 cubic feet) and I have 2400 watts @ 4ohms from a Behringer EP2500 to work with. Im also highly considering purchasing a DEQ2496 or other parametric equalizer for christmas.

The room is quite big, its actually a partitioned basement so I doubt room gain will play much of a role in the design.

Is my goal practical with only one woofer?

What design should I shoot for to achieve my goals? Linkwitz Transform? Ported around 15-16hz or a Transmission line? I've seen designs where they use multiple tubes within another to create an extremely long TL.
 
1185cm^2 surface area, Fs of 16hz, 27mm xmax
...pretty big displacement

I know it seems like a daunting task, but you sure it isnt up to it?

Another option, would be selling the 18" Avalanche and purchasing 4 Mach5 audio 18" subs (1029cm^2 surface area and a 12mm xmax). They would be wired to 4ohms stereo (each woofer receiving 375 watts from the EP2500)
 
My suggestion is to contact SteveCallas. I know he's on AVS Forum (avsforum.com), might be on here too, not exactly sure...I've seen him on other forums as well. If I were you, I'd seriously consider his Sonotube "LLT" design that he built for his Avalanche 18.

I currently have 2 Avalanche 15's, and plan to build a 300 liter sonotube for each, tuned to about 15Hz with 600 or 700 watts.

Also, make sure you talk with him about your room size. Perhaps it's a bit too large for that AVA18 to fill, but I seriously doubt it...just depends. If needed, he could help you come up with a good size for spl versus extension in your particular room. And...buying two used Avalanche 15's myself in mint condition from eBay, I'm well aware of how difficult it is to still find these things. Finding another 18 would be extremely rare, and I don't think it should be counted on during the design of this enclosure.

demon2091tb's suggestion sounds about right, and probably isn't far off. See if you can contact SteveCallas though.

Goodluck.
~ BHTX
 
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