Question on my DIY Tempest Design

Discussion in 'Home Theater Projects' started by Ron_C, Oct 22, 2003.

  1. Ron_C

    Ron_C Agent

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    Hi,
    Soon I will be looking to build a Tempest sub. Thi sub will be use almost exclusively for HT. I have thought about the sonotube design, but don't think I will have the 18" of spaces to put it. what I would need is something pretty thin(depth), say under 12", can be up to 18" wide and as tall as it needs to be. Due to my limited depth, this is forcing my to use a front firing design. So my question is, is the tempest suitable for a front firing setup, does it really matter? Also, Do you see a problem with my limited depth? As long as the internal volume is there, it shoudn't matter, correct??

    Here are some other questions I have. For the internal bracing, what size holes do you cut in the bracing and how far apart..ect. Does this change for each plan or is there a set way. Also, in my setup, where would be the best place to put the port? Does it really matter?

    My room is around 11' x 17' with 7' ceilings. It is acoustically treated and mostly flat. I would like to tune the sub to around 20hz.

    Thanks for the help.

    Ron
     
  2. Stephen Hopkins

    Stephen Hopkins HW Reviewer
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    That shouldn't be a problem, just realize your ports (if you port) are going to have to be on the top or possibly bottom if you put legs on it. Also, make sure to use a fair amount of internal bracing to break up standing waves.

    Good luck [​IMG]
     
  3. Ron_C

    Ron_C Agent

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    Thanks for the reply,

    Can anyone answer my second set of questions concerning the bracing and port placement. The sub will be standing on about 4" legs.

    Thanks,
    Ron
     
  4. Allen Ross

    Allen Ross Supporting Actor

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    for the bracing make them so you have at least 2 inches of MDF at the thinest points.

    I can comment on the front firing driver, mine works fine haven't had a problem with it (knock on wood)
     
  5. Matt Dolejsi

    Matt Dolejsi Agent

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    i'm also using a front firing tempest...sounds great
     
  6. TimForman

    TimForman Supporting Actor

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    My most recent sub is a Tempest in a modified Adire Alignment enclosure. 214 liter, 45"W, 20"H, 18"D, front firing with 2 4" ports also front firing. Works fine. I used four braces with five 4 1/2" holes in each brace. There's a couple pictures on .
    my site.
     
  7. Arthur_King

    Arthur_King Stunt Coordinator

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    If its for HT you could also use a PR to help with the low end (give ya more, which we all want). Mount a PR above the Tempest and you should be golden. How about a Sonotube? I guess its more than 12" deep, but if you could flex a little on that, you could have TONS of height and get lots of low end extension.

    Daffy Arthur King
     
  8. Ron_C

    Ron_C Agent

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    Hi everyone,
    Thanks for the great replies. I ran the tempest through WinISD and here is what I got. It is tuned to just under 20hz.

    Driver : Tempest
    Vas : 317.0
    Qts : 0.38
    Fs : 18.80
    SPL : 89.10
    Number of drivers : 1
    Box type : Vented
    Box size : 260.2 l
    Tuning frequency : 19.99 Hz
    Vent : 1 vent(s)
    0.157 m length for each
    0.102 m round


    Relative
    Freq Gain SPL
    [Hz] [dB] [dB]
    20.00 -3.10 86.00
    25.00 -0.64 88.46
    30.00 -0.17 88.93
    35.00 -0.09 89.01
    40.00 -0.08 89.02
    45.00 -0.08 89.02
    50.00 -0.08 89.02
    55.00 -0.07 89.03
    60.00 -0.07 89.03
    65.00 -0.06 89.04
    70.00 -0.06 89.04
    75.00 -0.05 89.05
    80.00 -0.05 89.05
    85.00 -0.04 89.06
    90.00 -0.04 89.06
    95.00 -0.04 89.06
    100.00 -0.03 89.07


    Does this look right to you? Is there any thing I should change. This would make the internal dimensions 12"x18"x74". Thanks.

    Ron
     
  9. Patrick Sun

    Patrick Sun Studio Mogul

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    Maybe the only thing would be to see what length you'd need if you used two 4" wide ports to help with reducing port noise at high output levels.
     
  10. TimForman

    TimForman Supporting Actor

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    Ron,
    If you're going to do that you may want to consider an open-ended pipe. When heavily stuffed it takes on the characteristic of a transmission line. Check this:
    T-linespeakers
     
  11. Ron_C

    Ron_C Agent

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    I went back and changed it for 2 ports to slow the port air speed down, and now it is a lot better. Now the port lengths are longer though. Why is it that when you add more ports, the ports get longer?? Just curious.

    Here is the winISD data it produced. Everything look ok?

    Driver : Tempest
    Vas : 317.0
    Qts : 0.38
    Fs : 18.80
    SPL : 89.10
    ----
    Number of drivers : 1
    Box type : Vented
    Box size : 260.2 l
    Tuning frequency : 19.99 Hz
    Vent : 2 vent(s)
    0.388 m length for each
    0.102 m round


    Relative
    Freq Gain SPL
    [Hz] [dB] [dB]
    20.00 -3.10 86.00
    25.00 -0.64 88.46
    30.00 -0.17 88.93
    35.00 -0.09 89.01
    40.00 -0.08 89.02
    45.00 -0.08 89.02
    50.00 -0.08 89.02
    55.00 -0.07 89.03
    60.00 -0.07 89.03
    65.00 -0.06 89.04
    70.00 -0.06 89.04
    75.00 -0.05 89.05
    80.00 -0.05 89.05
    85.00 -0.04 89.06
    90.00 -0.04 89.06
    95.00 -0.04 89.06
    100.00 -0.03 89.07


    Thanks,
    Ron
     
  12. Patrick Sun

    Patrick Sun Studio Mogul

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    As you have larger cross-sectional area in the porting (i.e. adding another port), the length of the port for the same tuning frequency (and same internal volume) will need to be longer. That's just how the math works out.
     

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