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10 speakers in series/parallel? Dodecahedron design.

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  • #16
    Re: 10 speakers in series/parallel? Dodecahedron design.

    If still want to use 10 drivers and can find a suitable 16 ohm driver, you can run them in series pairs, and all 5 pairs in parallel to bring you to 6.4 ohms nominal.

    If you're looking for flat response, you're most likely going to need some EQ at the low/mid freq. You'll actually need some "reverse BSC". Each driver by itself will be fairly omni below 1 khz, especially below 500 Hz. With that many drivers in an "omni" configuration, they will all contribute to output as all drivers will be summing together in all directions. So, when standing at a specific point and listening to the speaker, you will have all 9 or 10 drivers contributing to the low end, and somewhere around 1-3 contributing to the high end where the individual speakers are very directional. This will give you a pretty big boost at the low end.

    Another phenomenon you will probably notice is a dip somewhere in the 600-1000 Hz range which is dependent on the diameter of the enclosure. The drivers will still be radiating omni, but the drivers on the back-side will be out of phase with the drivers on the front in relation to the listening position, so there will be some amount of cancellation there resulting in a dip in the FR.

    Also make sure you use some acoustic stuffing in the enclosure to minimize back-waves from opposing drivers. If you don't, you may see some dips in the upper frequency response due to back-waves being out of phase.

    I agree with jhollander that this could be a cool project. I think a 9 or 10 driver "ball", pole mounted on top of an appropriate sized sub could be a sweet speaker to put out in the middle of your back-yard.

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    • #17
      Re: 10 speakers in series/parallel? Dodecahedron design.

      Yeah, I did take note of acoustic stuffing. The instructables build used it, and I probably will too, if I can get my hands on it.

      The phenomena you describe are interesting. Definitely see how it goes when it comes together.

      I'm not too keen of having it being suspended on a pole, as I want it to have some degree of portability/boombox kinda feel. If I have 9 drivers, the pole won't be necessary unless I want to get a more advantageous listening position.

      I won't be able to put this together that quickly though. I'm in the middle of mandatory national service, which means my hands are pretty much tied on weekdays :( I'm still very much planning and getting a feel for the project direction.

      Rest assured I'll be updating this thread when I start doing some real work.

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      • #18
        Re: 10 speakers in series/parallel? Dodecahedron design.

        I drew up a rudimentary model in sketchup so my idea becomes a little clearer:

        Click image for larger version

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        I'm not sure what the final colour or button cluster at the top will be like, but this is a pretty good idea of what I'm going for (:

        The empty faces are meant to have speakers on them. I got lazy to draw them all, but I hope you guys get the idea!

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        • #19
          Re: 10 speakers in series/parallel? Dodecahedron design.

          Acoustic stuffing is just the "polyfill" found in your typical pillow (can be bought at Wal*Mart). Fiberglass insulation works just as well (but it's a little pickier).

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          • #20
            Re: 10 speakers in series/parallel? Dodecahedron design.

            I don't live in the states, but I'm sure pillow stuffing won't be an issue Thanks!

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            • #21
              Re: 10 speakers in series/parallel? Dodecahedron design.

              I currently have a 5V BT module on hand, which I'll be adding inside the case. Would it be possible to run it off the 5VGEN pin of the amp, or should I run it off the battery with a voltage regulator?

              I imagine running off a regulator would create lots of heat.

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