Tumult enclosure choice

Discussion in 'Home Theater Projects' started by Brad Dixon, May 28, 2003.

  1. Brad Dixon

    Brad Dixon Stunt Coordinator

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    Good news is I got a bonus from work. Bad news is this has me wondering if I should build a 120L(may be able to squeeze out 130L) PR Tumult or stick with my 85L sealed plans.

    The sealed box I have planned will fit under our current end table. If I go the PR'd route the enclosure would have to serve dual purpose as an end table. It would only have a lamp on it but of course when company comes over I'm sure a few drinks will get placed on it. Could I build a box stiff/sturdy enough so that things won't vibrate off it without it weighing 200lbs?

    I saw the recent post about sturdy enclosures but wasn't sure with these PR's having so much weight to them if it would have even more affect on vibrations.

    I'll be using Baltic Birch 13ply(3/4"?) and powering the sub with the keiga amp from acoustic-visions.

    I'm getting excited, hopefully the amp will be here tomorrow.

    Thanks,
    Brad
     
  2. Jonathan_D

    Jonathan_D Stunt Coordinator

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    I would think to get it as dead as you'll want it, you'd want to combine 3/4" MDF with the Baltic Birch.
     
  3. Seth_L

    Seth_L Screenwriter

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    Use the BB. Servodrive's contrabass is capable of similar SPL's and uses only 1 layer of 3/4" BB. It seemed extremely rigid. I wouldn't use MDF at all because it is not a stiff wood it's just extremely dense. Using MDF you make the box so dead it can't resonate. Net effect extremely heavy box (2 layers of 3/4"). Using BB you can make a box so stiff the resonant frequency is so high it's out of the range that the sub will be producing.
     
  4. Jonathan_D

    Jonathan_D Stunt Coordinator

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  5. Seth_L

    Seth_L Screenwriter

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    It all depends. The PR's should be placed in an opposed fashion so the moving mass cancels out between them.

    You still have the mass of the driver moving, but I would think that 345grams shouldn't have that much of an effect on a 100+ lbs enclosure. I can't say for sure though. I know the Contrabass I heard was rock solid, but it has opposed PRs and drivers, so all the moving mass is cancelled out.

    I would think putting things on top of the subwoofer is asking for trouble. Even if they don't vibrate off they may resonate from the extreme SPL from being so close to the driver.
     
  6. Jonathan_D

    Jonathan_D Stunt Coordinator

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  7. Seth_L

    Seth_L Screenwriter

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    There's always velcro. [​IMG]
     
  8. Brad Dixon

    Brad Dixon Stunt Coordinator

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    Well we(father and I) started cutting today. I decided on 27x22.5x19 external. I decided I really would like to try a low Q design(unibox says 146l to 125l for .5 to .52 qtc). My internal dimensions are 24x21x17.5(we're doubling up the speaker and amp baffles).

    What I had planned was 3 braces (3/4" BB) spaced on 6" centers. He thought since the amp doesn't do anything there's not a real need to double that baffle up so why not go with 4 braces on 4" centers.

    This would still leave 1.5" speaker baffle but the rear baffle where the amp will be mounted would only be 3/4". This will change the internal volume slightly but that's not a problem.

    The braces look like those from a clone audio sub(I think that's the one). He doesn't normally build enclosures so he told me to see what would be the more preferred/used route.

    example:
    Code:
     3 braces
     ---------------------------
     ||| || || || ||| 
     ||| || || || ||| speaker baffle 
     ||| || || || ||| 
     ||| || || || ||| 
     ---------------------------
     
     4 braces
     ---------------------------
     || || || || || ||| 
     || || || || || ||| speaker baffle 
     || || || || || ||| 
     || || || || || ||| 
     ---------------------------
     

    Thanks,
    Brad
     

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