Building a box

Discussion in 'Home Theater Projects' started by Anthony_I, Sep 17, 2003.

  1. Anthony_I

    Anthony_I Stunt Coordinator

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    Ok so in a few hours i will be going out to buy the wood required ot build myself a speaker box for my speaker.

    Now the company recommends a box of 0.9 Cu. Ft.
     
  2. Darren_T

    Darren_T Second Unit

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    I don't know the details of your situation but here is what came to mind.

    1. I'd ditch the car sub driver and go with one meant for home application unless you don't have a choice.

    2. I'd model the driver or supply the specs of the driver here and ask someone to model it for you.

    3. Take the advice of the people here...they've never steered me wrong. If you get some feedback on the driver specs and suggested alignments pick the alignment that best fits your listening habbits.

    4. Build with confidence [​IMG]
     
  3. Brian Bunge

    Brian Bunge Producer

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    Darren,

    We've already been through steps 1-3. I suggested a Shiva for $35 more than he paid for the car sub. I guess the $35 is better spent elsewhere![​IMG]

    I'm the one that suggested the 3ft^3 box for a Qtc~.7 vs. the .9ft^3 enclosure which was in the high .8 range.

    So basically it comes down to this: do you want loud, impressive boom, or do you want something with a fairly flat frequency response graph that you can stand to listen to more than just rap or techno music with? If you want the latter, then go with the 3ft^3 enclosure. If you want the former, go with the .9ft^3 enclosure.

    Hell, MDF is cheap, build both and then choose![​IMG]
     
  4. Darren_T

    Darren_T Second Unit

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    Hi Brian,

    I figured that had probably been gone over [​IMG]

    Anthony,

    Do what Brian says! Bad boy! If you don't learn to listen I'm sending you to your room....wait, is your system in your room? If so don't go there. Too much fun. [​IMG]

    I'd proceed with confidence then since Brian won't steer ya wrong.
     
  5. Dave Poehlman

    Dave Poehlman Producer

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    [edit] Oh, nevermind... looks like it was resolved by the time I got done typing. CURSE YOU SLOW FINGERS!
     
  6. Anthony_I

    Anthony_I Stunt Coordinator

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    Well brian i will take your advice and go with a 3 Cu Ft box.
    Thanks for the quick replies, This will allow me time to make any adjustments to measurments before the wood is purchased.

    as for getting a new speaker...well thats a little out of the question since i already own the Octane.
     
  7. Darren_T

    Darren_T Second Unit

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    Let us know how it goes. I'm sure we'll all be interested to see how this car driver works out for you.
     
  8. Anthony_I

    Anthony_I Stunt Coordinator

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    oh and brian, bassbox pro lists the QTC of the 3 Cu Ft box as 0.3529 and with a .9 Cu Ft box it lists the QTC as 0.5277

    Im guessing that 0.3 is better.

    and it wasnt that the $35 was better spent elsewhere, its that i had already ourchased the Octane
     
  9. Brian Bunge

    Brian Bunge Producer

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    Anthony,

    I re-ran your driver's specs in Unibox and I'm still getting the same thing. For a Qtc=.707 you need a 95L enclosure. With bracing that'll give you roughly 3ft^3 of internal airspace.

    I don't know why BassBox would give such radically different numbers.
     
  10. Anthony_I

    Anthony_I Stunt Coordinator

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    Probably because im not putting in any bracing or damping.
    I calculated a 3Ft^3 box by entering the Vb, and then adjusting measurments to more rounded figures that added up to 3Ft^3.

    This is the EXACT size of my box as listed by bassbox.
    3.02593934475105 Ft^3

    So i could add a brace without losing too much volume?!
    I will add the chart of my normalized amplitude reponse in a bit.
    -----EDIT-----
    (I cant attatch an image so i will have to find a place to host it before i can post it, and im off to work in a few mins so it will have to wait until later)
     
  11. Brian Bunge

    Brian Bunge Producer

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    I'd add a couple of braces at least. I came up with 95L with zero stuffing, so if you added a couple of pounds of polyfill you would still be fine.
     
  12. Anthony_I

    Anthony_I Stunt Coordinator

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    Now would you mind explaining to me what exactly a brace will do.how it will help, where a brace should go, and what the hell does stuffing my box full of damping material do exactly?

    muffle my sound? make it better? slightly worse?

    the damping issue is where im lost.
     
  13. Darren_T

    Darren_T Second Unit

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    Damping is either reinforcing the enclosure to eliminate vibration or resonance or applying a damping material such as BH5 or foam to the inside walls of the enclosure. Either will reduce the resonance of the enclosure. Resonance is bad, it colors the sound. Take a look at the Adire Audio alignment drawings for a good example of bracing.

    Darren
     
  14. Anthony_I

    Anthony_I Stunt Coordinator

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    where can i find those drawings?

    and since were talking about resonance, then what is the tuning frequency of a vented box?

    is that the freqency at which the box(or vent?) begins to resonate? or is it the frequency that the box will resonate at all the time?
     
  15. Brian Bunge

    Brian Bunge Producer

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    Bracing helps to keep the panels of the enclosure from resonating, or more exactly, pushes their resonant frequency above the bandwidth that the subwoofer will be operating.

    Stuffing the enclosure helps absorb the backwave of the driver and effectively makes the box "appear" to be larger to the driver.

    Concerning vented enclosures, the tuning frequency is a product of the enclosure size, port diameter, and port length. It's basically the frequency at which the port resonates. Think about blowing across the top of a Coke bottle. The sound you here is the frequency at which the opening resonates. Different sized bottles will sound different because they are resonating at different frequencies.
     

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