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Need help with LLT please...

1951 Views 3 Replies 2 Participants Last post by  GPM
I would like to build the LLT. I will be using the Ultimax 15" DVC. Also have (4) 4" x 18" flared ports to use if necessary. The enclosure will be behind the couch so it will have to be narrow 18"/20" but up to 30/32" tall and 50/60" long. Recommendations for speaker/port location would be helpful. Also have 4" elbows (90 degree) if needed. Maybe fire the sub down and ports forward but the use of the the elbows would probably be needed with the limited room. I have built other subs but not one of this size. Any help with this matter would be greatly appreciated.
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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.


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Thanks for the reply. I forgot about the sag issue so I went with front firing Ultimax 15". Around 14 ft3 ported enclosure with (4) four inch ports that measure roughly 18" each (side firing). I am extremely happy with the results and increased the low end (20 to 25 Hz) by at least 10db if not more. Thanks again for the help.
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