Help with Transmission Line design for Tumult

Discussion in 'Home Theater Projects' started by DavidFun, Feb 27, 2004.

  1. DavidFun

    DavidFun Agent

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    Is it even possible to build a TL Box for a tumult. I currently have it in a 2.5 cubic foot box. It is nice, but I want to try something different and don't want to dump money into PR's. What about a TL? Any thoughts experts.

    David
     
  2. Travis Cain

    Travis Cain Stunt Coordinator

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    OOOooooo.. I know it is possible, but I don't have a clue how to design a properly tuned line but I sure hope someone can help you. TL's are a beautiful thing and are much too often overlooked.

    And if you want to impress your friends, you can tell them you've discovered Bose's secrets and designed your own "acoustic waveguide technology" subwoofer.
     
  3. ThomasW

    ThomasW Cinematographer

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    What are you trying to accomplish? Louder? Lower?

    T-lines IMO are a pain design, and a bigger pain to build and certainly not for noobies.....

    Just do a google search for "quarter wave loudspeakers", "T-line loudspeakers" and you find enough links to get lost forever.....

    The easy part is the line length. It's simply 1/4th of the wavelength you want to use for the tuning frequency.
     
  4. Allen Ross

    Allen Ross Supporting Actor

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    i was asking around if i could do this with my tempest for shits and giggles and i believe you need to look for a driver that has a relatively high EBP in order to have a box that isn't the size of your room.

    I am just going off of my memory, so it might not be 100% true, i just remember a guy did a quick box volume and it was going to turn out the size of my dorm room. I contemplated doing it (turning my dorm room into a 1/4 wave 20hz LT) for about a day or two, i have some rough plans [​IMG]
     
  5. DavidFun

    DavidFun Agent

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    My goals are to build a sub that sounds fantastic, and plays as low as possible. I would like to get more out of the Tumult than the sealed box can provide. I am a skilled woodworker, and was looking for another project that wouldn't cost much. It sounds like a TL tuned to 18 hz would be freakin huge. Maybe it's not really feasible.
     
  6. Mark gas

    Mark gas Second Unit

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    why not go ported?
     
  7. DavidFun

    DavidFun Agent

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    I probably will. I guess it will have to be a slot ported box. I just wanted to ask about a TL design before I built a ported box.
     
  8. Jack Gilvey

    Jack Gilvey Producer

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    What advantage are you looking for with a TL over other options?
     
  9. Allen Ross

    Allen Ross Supporting Actor

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    my interest would be to get that SPL up above 87, i can't stand inefficient driver.
     
  10. ThomasW

    ThomasW Cinematographer

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    Then I guess you shouldn't have purchased one, it's that Hoffman's Iron law thing..... [​IMG]

    You'll gain a little efficiency going with a bigger box. And going ported will add some additional low frequency output. But nothing aside horn loading, is going to actually increase the efficiency of a Tumult.
     
  11. TimForman

    TimForman Supporting Actor

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    A true TL design would make the line length equal to 1/4 wavelength of your tuning frequency. If you want to tune to 18hz you'd need a line length of 188 inches. I've made a "cheater" TL with a Shiva that's 72" long. Anyway, a Tumult TL, even folded, would be longer than your couch.
     
  12. Pete Mazz

    Pete Mazz Supporting Actor

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    Yea, they get big! I did this with a Tempest tuned to ~28Hz, IIRC. Line length was like 122".


    [​IMG]

    Stood 78" high with the base on it.

    Pete
     
  13. TimForman

    TimForman Supporting Actor

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    There's no avoiding it.
     
  14. Seth_L

    Seth_L Screenwriter

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    Sure there is just ask all the people with Sunfire subs. [​IMG]
     
  15. Allen Ross

    Allen Ross Supporting Actor

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    Pete what did you use to model how that tempest enclosure? how does it sound? are you happy with it?

    AND DAMN THAT SOME STUFFING!!!
     
  16. TimForman

    TimForman Supporting Actor

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  17. TimForman

    TimForman Supporting Actor

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    I used 1 lb per cubic foot in my Shiva.
     
  18. Brett DiMichele

    Brett DiMichele Producer

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    Ohh Seth is just babbling again..

    The Sunfire does not circumvent Mr.Hoffman's law in any way.
    It's a driver with tons of excursion, fed tons of power in
    a very small box... It works... It may have too much distorsion
    for some listeners but damn that Iron Law thing again.. And
    yes it's heavily EQ'd as well [​IMG]

    Doesn't seem much different than putting any driver in a
    smaller than required enclosure and needing an LT Circuit to
    get any useable output way down low eh?

    [​IMG]
     
  19. Elza

    Elza Auditioning

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    Pete,

    I'm thinking about building a subwoofer to use for about 50% Music/50% HT. How did your TL sub turn out? Would you use the same design again?

    Thanks,
    Elza
     
  20. Seth_L

    Seth_L Screenwriter

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    Apparently you missed my sarcasm. Some Sunfire owners on AVS think that the Sunfire bends Hoffman's law through technical advances. Hence my remark.

    Apparently they think their Sunfire is every bit the equal of something like a big driver, in a big box, with lots of power. After all it plays at 111dB and goes down to 20Hz.
     

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