Educate me about subs... (building a box for a pair of ID subs)

Discussion in 'OT Technology' started by turbo35, Feb 4, 2004.

  1. turbo35

    turbo35 haters gonna hate

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    So, I'm looking at tech info for Image Dynamics subs (probably going to get 2 IDQ10 D4 V.2's, IDQ 10" dual 4-ohm voice coil new version). What affect does the difference in the box volume on sound output, as far as actual output is concerned? Does a bigger/smaller box just shift the response curve over? I want as even a curve as possible to replicate the song as accurately as I can, I'm not a big boom-boom bass guy or whatever, so I'm definitely going sealed enclosure, just trying to figure out what size to build em.

    Here's the link to the spec sheet for the subs I want... IDQ10 D4 V.2

    Also... Can someone explain the whole "-3dB" thing to me? Is that some sort of a standard notation for measuring sub output at a given frequency or something? It looks like they use that to measure the difference between enclosure volumes, but I don't really understand what they're pointing out. :dunno:

    Also... anyone run these subs? Any firsthand experience with the quality? Suggested prices? I'm gonna be running these bridged on a Zeus Z400 (400w x 1 @ 1 ohm), think that'll be fine?

    Thanks!
     
  2. 04

    04 Guest

    The larger the box, the lower your mechanical power handling. Your woofer system also becomes more efficient and does not need as much power to reach its mechanical limits at lower frequencies. A smaller box increases your mechanical power handling, but also can cause peaking in the frequency response, that will add to the output above system resonance.

    Bottom line is that you will most likely want to go with the largest reccomended sealed box they have. For those particular woofers I would go with around a 1 cubic foot box per subwoofer sealed assuming they will be getting 200 watts each.

    The -3dB point is where the woofer begins to start rolling off. Its also known as half power. In a car, the -3dB point is usually well below 20hz so it doesnt matter very much.

    There is a set of parameters that can be derived to determine what the "basic" curve of the speaker will be, they are known as Theile small parameters. They allow you to make a "rough" estimation of what the subwoofer system will sound like when you place it in various sized boxes. The main downside to it is that it only holds true at low power and when you increase input power considerably, the parameters change a bit.
     
  3. turbo35

    turbo35 haters gonna hate

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    These are actually the subs I'll be using... you think I should do 1 cu/ft each, even tho a "large" enclosure is .7 cu/ft? The subs will be bridged on the Zeus, so should be pulling about 400w RMS, so 200w each...

    What I'm really looking for here is something that will match the SQ of my system well (8 volt Eclipse head, Alpine amp powering MB Quart components). It's not an extremely loud stereo, but it's pretty damn accurate, so I just want something that's not gonna be "peaky" at certain frequencies, etc. I tried messing around with a program that's supposed to help calculate the best box volume (WinISD), but I couldn't really figure it out.

    Any other suggestions?
     
  4. 04

    04 Guest

    Yeah you could use a 1cuft enclosure for each even though the largest reccomended is .7cuft. You will get a smoother frequency response with a larger enclosure all other things being equal. However, even a .7cuft box would work fine, so its really up to you, the .7cuft box after all would take less space.

    IMO most people don't use WinISD correctly anyways, so I wouldnt worry about it. I would just put them in an enclosure of around .7 - 1 cuft internal airspace, and I bet you will be pleased.
     

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