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Thread: New Voice of Theater owner needs some advice and help

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  1. #1
    Junior Member
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    New Voice of Theater owner needs some advice and help

    Hello Lads,
    I joined the big stupid speaker club, and now own a pair of Altec A7 VOT speakers
    My local college got some money in their budget and upgraded their sound system. They auction off all their old stuff, and things students leave behind, which is amazing in itself.
    I won a pair of VOT cabinets with 515B woofers and two pair of horns with 288C drivers, and one with 9803B horns and a pair with 311 60 horns.

    I used an extra Pioneer HPM 100 crossover to test them at home, and in a over used word they are "Awesome" I am making room for them in my house as they are going nowhere.

    I need some help, as in my searches, a lot of reference to "bracing the boxes" and adding insulation.

    There is no doubt they need bracing and a whole lot more insulation, as a volume increase over normal listening really resonate the top and sides.

    I ordered a Behringer crossover so I can play with roll off points, and I got a great price on the Jabo horns from germany

    So How does one "brace" these cabinets? and does stuffing the flares with insulation kick up the Bass a little?

    Thank you,

    Donald Bowman

  2. #2
    Maron Horonzakz
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    No stuffing the flairs will do nothing for the bass,,,The rest of the cabinet is a bass reflex,,,You can double the thickness of the sides of the cabinet,,from the outside,,for stiffness..

  3. #3
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    Sounds like you have A5's not A7's. The cabinet is the same.

  4. #4
    Dang. Amateur speakerdave's Avatar
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    I think those diagonal braces to the center of the back need to land on a panel that will stand free when the back is removed and draw tight with additional screws through the back panel when it is in place. Woofer access is achieved by taking off the back panel.

  5. #5
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by speakerdave View Post
    I think those diagonal braces to the center of the back need to land on a panel that will stand free when the back is removed and draw tight with additional screws through the back panel when it is in place. Woofer access is achieved by taking off the back panel.
    Good point... I didn't really think it through. I can tell by looking at the Altec drawings that they simply didn't pay much attention to panel resonance at all though. No wonder they sound so colored. Doubling up the walls as Maron suggests would be the easiest fix but it will only go so far.


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  6. #6
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    Panel resonance and bracing

    Hello Lads,
    Thanks for th input, ireegardless to the first response, I had a bunch of foam sheets here that I use for packing gear to sell.
    I stuffed the insides of the flares, and found a full 50 percent reduction to panel resonance on the top and upper third of the cabinets, I also noticed a bit fuller bass, with more bass from the bottom port.

    I have a pair of Pioneer HPM 100's that from the factory have no inulation on the top inside and the top 1/3 of the back. Last year I installed a dense sheet foam in these areas and had a dramatic increase in the bass, and a much brighter treble. Following this logic, I guess I will reinforce everything inside, and fill the flares with expanding Marine foam that comes in a very dense formula, and install a thick layer of insulation in the rest of the cabinet. None of whivh could hurt.

    I am entertaining the idea of separating the upper and lower cabinets internally, and installing a JBL 2245 sub woofer in the bottom.

    Doing sloppy math, this seems to work out the same as having an Altec 612C cabinet laid sideways on the bottom with a sort of 816A cabinet on top.
    Have to work out venting them, but seems viable.
    Seems like a lot of work, but there is just something about these speakers that gets me and won't let go.

    Thanks,
    Donald

  7. #7
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by Mrmonster11 View Post
    So How does one "brace" these cabinets?
    I would use 2 by 3 or 2 by 4 kiln dried fir or hardwoods and follow a pattern something along these lines... the red lines are merely a schematic. They need to be glued and screwed to the panels and the cross braces well anchored to the vertical and horizontal panel mounted braces.


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