Greets!
Seems like decades since I've seen any interest in EBS/LLT sub alignments and ATM can't recall what, if any specific design routine there is for the LLT, but based on a ~ 'extended bass shelf' [EBS] alignment; at a glance we're looking at ~323 L net tuned to ~0.707x Fs = ~14 Hz [max practical reflex tuning], which ignoring any room/boundary gain, limits power handling to ~400 W, so well within your space allotment.
This in turn requires an extremely large/long vent [10" i.d./~76" long depending on boundary loading] to keep its air speed [mach] < 5%, so recommend using dual 15" PRs; or if not in the budget, then my preference of morphing the box/vent into a single fold, inverse tapered, TQWT with a [terminus] 'vent' area [Av] = [Sd].
Note that while the driver's calculated down firing sag is within the ~5% limit, in such a large box it will tend to not perform as well as when vertically oriented once well broken in and driver/vent location will be based on the chosen alignment, closeness to any large furniture and/or room boundaries.
GM
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Seems like decades since I've seen any interest in EBS/LLT sub alignments and ATM can't recall what, if any specific design routine there is for the LLT, but based on a ~ 'extended bass shelf' [EBS] alignment; at a glance we're looking at ~323 L net tuned to ~0.707x Fs = ~14 Hz [max practical reflex tuning], which ignoring any room/boundary gain, limits power handling to ~400 W, so well within your space allotment.
This in turn requires an extremely large/long vent [10" i.d./~76" long depending on boundary loading] to keep its air speed [mach] < 5%, so recommend using dual 15" PRs; or if not in the budget, then my preference of morphing the box/vent into a single fold, inverse tapered, TQWT with a [terminus] 'vent' area [Av] = [Sd].
Note that while the driver's calculated down firing sag is within the ~5% limit, in such a large box it will tend to not perform as well as when vertically oriented once well broken in and driver/vent location will be based on the chosen alignment, closeness to any large furniture and/or room boundaries.
GM
