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Looking for help with desing on tempest

Discussion in 'Home Theater Projects' started by andrewPerc, Jan 7, 2005.

  1. andrewPerc

    andrewPerc Auditioning

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    I am looking for some info on some possible issues I'm having with design of a 4th order bandpass box and a tempest 15" driver.

    Note: I have built tons of boxes in the past but nothing within the last 8 years, so it is an understatement that I'm rusty with design let alone with the math. After say that here goes.

    I want to use a 1 tempest driver in a 4th order bandpass design and then move to 2 in a isobaric design depending on the output I can achieve from a single driver.

    I have been using the equations that I found off the “DIY subwoofer page: by Brain Steele” and I have some concerns/questions about the results obtained. With the use of the white paper for the tempest driver I calculated the box volumes for both the ported and seal side of the design. I received the following values:

    Vented chamber 94.503 liters
    Sealed chamber 79.847 liters
    This was with a lower 3dB cutoff frequency of 28 Hz and a gain of 3.4.

    When I calculate for gain of zero I get the following values at the same lower cutoff frequency:

    Vented chamber 94.503 liters
    Sealed chamber 134.641 liters

    Neither of these volumes seems to be appropriate for a driver of this nature. A sealed chamber for a high power 15” with the T/S numbers of such I would suspect would run a lot more efficient in a much larger enclosure. I triple checked my math and the techniques to obtain these values and all seem to be correct.

    I would like to know if anyone has tried this. What type of volumes are you guys getting with sealed boxed with a similar cutoff frequency?
     
  2. Jack Gilvey

    Jack Gilvey Producer

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    I don't have a clue about bandpass boxes, never had any interest in trying one. I would recommend using Unibox to check your numbers, though...it's an outstanding program and includes BP simulation.
     
  3. Patrick Sun

    Patrick Sun Studio Mogul

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    In the past, people have had good experiences with the Tempest placed in a polyfill-stuffed 5 ft^3 enclosure, and rely on room gain to get that last bit of low end bass.
     
  4. andrewPerc

    andrewPerc Auditioning

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    So I can go with a sealed design of approx 5 cuft to obtain the same gain to freq cuttoff ratio?
     
  5. ThomasW

    ThomasW Cinematographer

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    IMO bandpass are the worst sounding subs on the planet, one note bass, poor definition, poor transient response. (Bose designs are bandpass)

    Since you have a Tempest and since Adire's already done a bunch of designs, just use one of their applications
     
  6. andrewPerc

    andrewPerc Auditioning

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    I'll look into it. It seems that every program I find or make for that matter changes the amount of volume needed anyway.

    Thanks for your input.
     
  7. ThomasW

    ThomasW Cinematographer

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    If you insist on modeling your own box download the free version of LspCAD from the Adire website, or as Jack suggested use Unibox.

    The results from LspCAD and Unibox will be consistant.
     
  8. andrewPerc

    andrewPerc Auditioning

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    I will dload the LspCAD and see what it turn out.

    It seems to me, with my not to up-to-date knowledge of these subs, that they will not be able to product the output that I need in the space that I have.

    Can anyone recommend a driver for my application?

    I want to be able to have a driver or a set of drivers that will be able to take up to 800 watts each and fill 2700 sqft+. But will also have a good responce to lower power apps in smaller space, depending on the box design. From what I have been reading the tempest is the way to go, but will this driver be ablt to handle such a big room?
     
  9. ThomasW

    ThomasW Cinematographer

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    If your room really is 2700 sq, ft as opposed to 2700 cu ft, then you're looking at the wrong driver unless you plan on buying a 1/2 dozen of them.

    You need to be looking at a couple Tumult from Adire, or some of the larger drivers from AscendantAudio.com

    Once you've decided in a driver we'll walk you through modeling a box since these high excursion drivers a sometimes a bit tricky
     

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