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12" passive

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  • 12" passive

    Need to replace a 12" passive woofer from a optimus box.
    What would be an upgrade?

  • #2
    Re: 12" passive

    Consider the 12" Dayton SD315-PR passive radiator, SKU 295-496.

    A simple search for "passive radiator" on the Parts Express site turned this up without any trouble, and there's no reason that it shouldn't be enough for your application. You will need to tune the passive radiator for your box, by adding mass to it. Use WinISD to calculate the necessary length of a 12"-diameter port that would tune your enclosure to the desired frequency, and then calculate the mass of air in a vent of that length. Subtract the moving mass of the passive radiator from that value, and that will give you the amount of mass you need to add to the passive radiator to achieve the tuning you want.
    Best Regards,

    Rory Buszka

    Taterworks Audio

    "The work of the individual still remains the spark which moves mankind ahead, even more than teamwork." - Igor I. Sikorsky

    If it works, but you don't know why it works, then you haven't done any engineering.


    • #3
      Re: 12" passive

      Tater, I believe he was asking to replace the driver itself. Optimus offered a few "passive" subwoofer designs through the 90's.

      They are ported, dual 8 ohm voice coil designs.

      This guy might work out alright, although the Optimus enclosure will be pretty small for it. If memory serves, the Optimus enclosures ran ~1.5-1.8 cubic feet, and tuned around 35 Hz. The Dayton would give a satisfying "thump" installed in there, but eventually it might become too monotone for some people.
      Don't listen to me - I have not sold any $150,000 speakers.