Stage/sub

Discussion in 'Home Theater Projects' started by Brad E, Mar 29, 2005.

  1. Brad E

    Brad E Second Unit

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    I'm going to be building a stage that is 8'x 2'x 3'.(roughly)

    I want it to dual as my sub, adding 2 15's, front firing.(yet to be determined)
    Ported at the front also.

    Now would I be better off building one big box with the above dimensions? Or would 2 Adire boxes, which will fit inside the stage, be better?

    I've seen this setup before in an IB setup. The back of the stage opened into another room. Unfortunately, I don't have that luxury.[​IMG]
     
  2. Allen Ross

    Allen Ross Supporting Actor

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    depends on the driver that you are using and what is better for it, bigger box lower tuning or smaller box higher tuning.
     
  3. Brad E

    Brad E Second Unit

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    I've been looking at the Atlas 15's and the Tempest.

    The stage (excluding support, vents and driver) will be about 1359 L. This is many times bigger than what seems to be the norm.
    Now is this because of space constraints or do the smaller enclosures work better?
     
  4. Allen Ross

    Allen Ross Supporting Actor

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    depends on how you tune them and remember to subtract the displacement of the vents from the internal volume.

    As you lower the tuning on the enclosure, the delay is also reduced, if my memory serves, for the 270L Adire alignment tuned to about 18 hz the delay goes back down around 18ms.

    Also when you are taking about and enclosure that size you are almost dabbling on IB characteristics if you were to go sealed.
     
  5. Greg Monfort

    Greg Monfort Supporting Actor

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    Greets!

    At a glance, these are too large to vent unless you use a PR. Better IMO to build two sealed cabs loaded with the Avalanche 18. Better still, loaded with two Avalanche 15/cab. This setup approaches sub-bass horn performance.

    GM
     
  6. Brad E

    Brad E Second Unit

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    I've been doing quite a bit of research the last couple days and I'm almost at the building stage.
    On WinISD Pro with these two subs I'm getting very flat responces down to 13hz. For both subs there is only a 3db difference from 80hz down to 20hz with this enclosure.
    Both the Atlas and the Tempest are within 1db of each other until the 17 hz point.
    The Atlas trails off a little faster at this point, but is still within 3 db's of the tempest.

    I would love to go with the Avalanche 18's but they are just too expensive. And sealed is not really an option because I'm looking for more extension in the lower fq's.

    The 48ft3 will actually be around 38ft3 after bracing and everything else. Can't wait to get this thing finished.
    I'm stoked.
     
  7. Mark Seaton

    Mark Seaton Supporting Actor

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    While my first reaction would be to build boxes which slide under the stage, I figure if you make the deck out of double layer ply with staggered seams and plenty of bracing/joists, the vibration would probably work well as a shaker for the rear seats. [​IMG]

    With a box that large, you should consider just making a huge ducted port (rectangular/slot). Length won't be big problem in a space that large. Just remember that low vent velocity largely trumps flaring in most cases. Otherwise use a bunch of precision ports which Ascendant can supply you.

    My suggestion would be to use a pair with the 2 Ohm coil shorted. If this is a free standing riser without walls at the sides (8' width) I would go with a huge duct the heigh of the riser and running across the 8' length. Somewhat like the port is done on the Genelec HTS6. I would tune it to 13-14Hz and power it with 250-350W total.

    Enjoy!
     
  8. Brad E

    Brad E Second Unit

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    I was planning on using 4, 4" vents, 15" long flared on both ends. This will put the tuning at 14hz.
    For the shell I'll be using 1" mdf or baltic birch if I can find it. I can always put another layer over top if I have to, but I don't really want to because it's going to be heavy enough as is.
    For bracing I'm thinking of using 2x2's setup in a crosshatch pattern, essentially making a bunch of 1' cubes. 48 of them to be exact, except for the two 1' pieces I have to leave out for the drivers.

    Any thoughts on this? Will this be enough bracing?
    Thanks.
     

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