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building a diy ISO box?

Discussion in 'Backline' started by aviel, Sep 25, 2012.

  1. Shinozoku

    Shinozoku Senior Memory

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    Take a read into the science of acoustics and the usage of obtuse angles, the golden ratio, and Thiele parameters.
     
  2. egan.

    egan. daylightdies.com

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    I think the post you quoted impies at the least a rudimentary understanding of all of those priciples. My point was that companies employing engineers seem to ignore the glaring flaws in the physics of the conventional design.
     
  3. hsnyder

    hsnyder Harris Snyder

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    Yeah I have a good grounding and physics and at least know where to start. Thanks though :)
     
  4. Shinozoku

    Shinozoku Senior Memory

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    ah, I quoted the wrong post. Meant to quote the one talking about taking a more mathematical approach ><

    EDIT: Fixed.

    In the grand scheme of planning something like this, would it be useful to find a way to use the dimensions of the box to diffuse/cancel the "boxy" frequencies? If I recall correctly, these usually lie between 800-1600hz. So in working with a possible "golden box" that's properly insulated, one could use diffusion or even plan the box sides to be like/include Helmholtz resonators to absorb the offending frequencies and make the box more pure. Mid/upper mid frequencies don't require a huge volume to absorb, and low frequencies can be tamed with something like Owens-Corning 705.
     
  5. egan.

    egan. daylightdies.com

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    I think it's more complex than that because you are dealing with several issues including standing waves, the resonant frequency of the chamber, the resonant frequency of the cabinet itself etc. Obviously these factors vary greatly on what you are trying to do. In the instance of the randall style iso cab you also have the issue of the speaker cabinet section and the "room section" (the part with the mic) actually physically sharing 4 walls and all of their resonances. I don't know what the implications of that are.
    I believe to make a 4x12" iso cab using the golden ratio it would have to be around 11' long at which point you're just building a room. These issues and the lack of need for true isolation are what lead me to the "soft room" approach. Non parallel walls and tons of insulation help but unless you have serious money and space to invest you are trading problems rather than solving them.
     
  6. Lazzari

    Lazzari Chakachakalabuchaka

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    Slipknot used to use a Randall ISO cab (or a Rivera don't remember) for live shows
     
  7. Shinozoku

    Shinozoku Senior Memory

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    You have a good point. However, I was thinking more along hte lines of a 2x12 isolation box, like shown in the above video... Something that may or may not act as a box spring for a bed, or a workbench when not having blaring loud guitars coming out of it. And yeah, I realize what I suggested was overly simplistic, but it was simply thoughts off the top of my head. It would be cool to have a discussion on the subject, putting all our scientific brains together to find an ideal bedroom solution.

    Billy Gibbons of ZZ Top uses them. Runs his rack units into them, plus a Mojave Scorpion using a Heil PR40 in the cab. He also uses a rackmount EQ matching system to make each guitar he plugs into it sound as close as possible to Pearly Gates.
     
  8. sprack

    sprack Thread Killer

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    Hope this is right for this thread.
    I finished my DIY ISO cab last month. I based it on as much info and shots of the Rivera as I could find as well as a whole lot of guess work. 3/4" birch, air labyrinth, dims of the room in front of the speaker based on golden ratio, 5 degree offset on 2 planes for the speaker, 3" cellulose insulation. I have a 100W ampeg 12" in there for the moment just to stress it. It's not perfect, but it does bring the 2203KK down to useable volumes in the room even when I have it a 5-6.

    [​IMG]
    [​IMG]
    [​IMG]
     
  9. aviel

    aviel Member

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    any clips??
     
  10. sprack

    sprack Thread Killer

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    I'll do some this weekend and run a couple different amps through it. Work is too busy atm to get to it during the week.
     
  11. sprack

    sprack Thread Killer

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  12. AD Chaos

    AD Chaos MGTOW

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    Out of curiosity.. why Ch3, instead of 4?
     
  13. sprack

    sprack Thread Killer

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    On the Roadster I like the way Ch3 sounds a little less saturated. Chunkier.
     
  14. 006

    006 Member

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    Seems pretty cool, would love to hear what a V30 sounds like in there ;) ;)
     
  15. sprack

    sprack Thread Killer

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    I have one in the closet. I'll try to get that in there this afternoon and rerun it.
     
  16. jangoux

    jangoux Member

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    sprack, mind sharing your design?
     
  17. sprack

    sprack Thread Killer

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  18. jangoux

    jangoux Member

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    sprack, thanks for sharing! I read a thread at Metroamp's forum where one of the guys suggested the labyrinth on the Rivera are more complex, with further 'walls' to give more surface area to 'break' the sound waves (or whatever lol). Anyway, why the opening at the end of the labyrinth ?

    Also, what kind of sound absorber did you use inside it ?
     
  19. sprack

    sprack Thread Killer

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    jangoux, As far as I understand, the opening at the bottom is to allow the cab to breathe. Otherwise the speaker is getting pushed back by the air in front of the cone that it just compressed and back again as it distends. It would make sense that in the closed system you're going to muffle certain frequencies because of that and if there are standing waves that could be additive or subtractive in a way that compound this. I insulated the air labyrinth to diffuse a lot of the outbound. I don't know how the Rivera's labyrinth looks. No one's gonna do a cutaway on a $1000 cab to find out. I had to wing it with mine.

    The insulation is Bonded Logic's R13 cellulose.
    PRODUCT THICKNESS DENSITY MOUNTING 125HZ 250HZ 500HZ 1000HZ 2000HZ 4000HZ NRC
    R-13 3.5" (mm) A 0.95 1.30 1.19 1.08 1.02 1.00 1.15

    Really though I improvised in any of the areas of acoustic design. I plagued a couple forums looking for real science. No one gave useful answers. Cheated using some of the high end audio DIY calculators with a healthy cross section of what speaker info I could find on guitar speakers that I thought in some way resembled what I was going to use. Tuned the port for the frequencies I didn't want accentuated, by logic of "it's getting pushed out the bottom". Then cut, assembled, glued and prayed.

    Oh. And link for the V30 clip for 006.
    RoadsterV30_SM57-i5.mp3
    I tried to get the mic's as close to where they were based on the old pic. No guarantees though.
     
  20. jangoux

    jangoux Member

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    Isnt this (the labyrinth) much like how a car exaust silencer/muffler works ?

    [​IMG]

    Looks pretty similar to me.
     

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