plan on building a subwoofer,need some advice

Discussion in 'Home Theater Projects' started by Anthony*gw, Sep 10, 2003.

  1. Anthony*gw

    Anthony*gw Stunt Coordinator

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    This is my first diy project,my room size is 13x14,i have the jbl nsp1 II 5.1 package.the sub will be for about 80% Ht and 20% music,i like deep bass and i am going to use one 12" driver in a sealed box.can anyone give me any advice on box dimensions etc....... thanks [​IMG]
     
  2. Anthony*gw

    Anthony*gw Stunt Coordinator

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    i currently have a audiopipe 10" driver i a 13x13x14 sealed box and the bass sounds to boomy,i don't like the boomy bass at all i much prefer tight deep bass.this time around i will be building the box and i am going with a 12" driver(haven't decided what driver yet)and i want a sealed box big enough to give me that deep bass i am looking for. can anyone help me out.
     
  3. David Giesbrecht

    David Giesbrecht Second Unit

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    Adire DPL 12 in a sealed box between 2.5 and 5 cubic would work well.

    2.5 cubic feet would yield a box Qtc of 0.7
    5 cubic feet would yeild a box Qtc of 0.57

    The bigger box will give you tighter and deeper bass but will be large, the small box won't sound quite as refined and will roll off faster but will be smaller.

    To find the volume of the enclosure simply multiply the internal box dimensions and divide by 1728.

    P.S. Make sure you account for the volume taken up by bracing and the driver.

    hope this helps[​IMG]
     
  4. David Giesbrecht

    David Giesbrecht Second Unit

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    http://tools.autoaudio.com

    This is a quik online box and port calculator I found just enter the drivers TS parameters (Vas,QTS,Fs) and go![​IMG]
     
  5. Dave Milne

    Dave Milne Supporting Actor

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    Jack... you kill me [​IMG]

    Anthony, as David demonstrated... the appropriate box volume must be calculated from the driver's Thiele/Small parameters. The driver and box work as a "system".

    Your choices of drivers will be limited by the approximate box size you can tolerate, the desired bass output and extension, the amplifier power available, and what you're willing to spend. Generally the process of driver selection involves working through some simulations with tools like what David pointed you to.

    A search through this forum archives will probably give you lots of good pointers. If you want any further advice from forum members, you will need to be more specific on budget, power available, allowable box size, etc.
     
  6. Jim Griffin

    Jim Griffin Extra

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    I built a sub earlier this year with the Adire DPL12 driver and the RCMAkustik DT-300 digital amplifier. I uses a 15 inches cube sealed box which is heavily stuffed to bring the Qtc down to 0.71. This design models to be 3 dB down at 35 Hz but with boost and room gain it will go into the low 20's Hz very nicely. Remember the benefit of the lower response roll off for a sealed box--12 dB per octave so you get good bass well below the F3 point. The DT-300 has 6 frequency points wherein the gain can be boosted either 3 or 6 dB so you have adaptability to adjust for the roll off and room gain as you need.

    I'm very pleased with the results.
     
  7. Anthony*gw

    Anthony*gw Stunt Coordinator

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    i will like to get a basic idea of the dimensions for a sealed box to give me deep clean bass,housing a 12" driver.it does not have to be the exact dimensions,just the general dimensions one uses for a sealed box to get that nice deep bass.
     
  8. Brian Bunge

    Brian Bunge Producer

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    Jack and Jim's suggestions are both great ones, but until you pick a specific driver or a specific box size then no one's recommendations will mean a thing.

    Yes, Jack good! Jack box good! Jack funny, too![​IMG]
     
  9. David Giesbrecht

    David Giesbrecht Second Unit

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    There is no golden set of dimensions that will get you nice deep clean bass, internal volume and the driver used is all that really matters when it comes to sealed subwoofers and every driver has different set of parameters and will require different volumes to reach a desired Qtc.

    as for the boxes I mentioned housing a DPL12

    If you would like to use the mid Q (small box) I would recomened the following INTERNAL dimensions (16.5x16.5x16.5)
    outside dimensions would equal an 18" cube.

    If you would prefer the low Q (large box) I would recomend the following INTERNAL dimensions (20.5x20.5x20.5) outside dimensions would be equal to a 22" cube.

    If you don't like the idea of a cube, shape doesn't really matter in subs because the wave lengths produced by the woofer are much longer than any dimension of the encloser.
    So you can use any shape you like as long as the total internal volume stay's constant.

    PS if your volume is slightly over what I have stated it will only sound better just don't go smaller than 2.5 cubic feet if you want the bass to be tight and boom free.
     

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