A 150L approx vented Tempest???

Discussion in 'Archived Threads 2001-2004' started by PeterOS, Nov 25, 2002.

  1. PeterOS

    PeterOS Extra

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    Some might reply saying why bother building a different design, there is loads out there for the Tempest.
    Simply I need to come up with my own design because I need something that is smaller than the 194L SBB4 design but I also want it to be vented. I wanted something that would be about 140L - 170L, no larger anyway (since it would be approaching the 194L).
    Also is there any way (eqn's or something), where you can show/prove/calculate the apparent increse in volume by adding polyfill/insulation. I am sure there must be a variation from material to material, Maybe it is neglitable??? I need to make a smaller box than the 194L but could I stuff it a bit more than average to increse the volume ??? I need something a bit better/acurate than just typing in to a prgram "15% / 25% Fill" etc
    If there any others that have tried a smaller vented box, any info would be helpful. I know I lose out on a lower Res. Freq but what they hey, it will be for films 90% of the time.
    Any info greatful, not much help for me here in Ireland, other than the leprechauns out the fields[​IMG]
     
  2. Jeremy Stockwell

    Jeremy Stockwell Supporting Actor

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    Peter,
    Check Pat Sun's Sunosub III site. He used a Tempest in Approx. 6ft^3 (170L) that turned out OK. He did have to (And I quote, "Stuff the hell out of it" but the end result was good.
    Check the "quote" link above, it has some additional information about your fill question.
    JKS
     
  3. PeterOS

    PeterOS Extra

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  4. Jeremy Stockwell

    Jeremy Stockwell Supporting Actor

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    Which link won't work? The one you list isn't one to which I referred.

    OK, I see now. I don't know why that link doesn't work. It's probably just old. I was really referring to the information in the HTF thread itself though instead of the link posted in the thread. I think the information that is there answers some of your questions.

    JKS
     
  5. Jonathan M

    Jonathan M Second Unit

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    Hi there Peter,

    Just something to keep in mind: If you go too small on your volume, you are much better off going sealed - vented will give you little extra extension, and, due to the 4th order rolloff, will have far worse characteristics such as group delay (As the phase is changing rapidly due to rolloff.) Model the Tempest in the box you are wanting in Unibox (do a google search if you want it), and do some sealed comparisons as well. You can play around with the Fill parameter to give you some idea of the response. I've found that, in general, moderate stuffing is fine, but if you need to stuff it too much you start loosing the only real advantage of a vented box - lower extension.

    I don't have Excel on this machine (Am at work on a Linux box) otherwise I'd have a look myself at how it models.
     
  6. Jeremy Stockwell

    Jeremy Stockwell Supporting Actor

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    Jonathan makes a good point. At some point, too much stuffing will eliminate the advantages of using a vented enclosure. At that point, you might as well go sealed. Exactly where that point is, I don't know. I guess that is now the question to be answered.

    Still though, Patrick seemed pleased with his small, vented, very stuffed, Tempest, so perhaps he will come to save the day by responding.

    JKS
     

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