IB sub parameters

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  • Brandon B
    Super Senior Member
    • Jun 2001
    • 2193

    IB sub parameters

    Dad's doing a major remodel over the next year, and his "media room" is a real good candidate for a 4-6 shiva IB sub, and I've got him to agree.

    Knowing little about these, what are the factors used to determine box volume, dimensions, opening size etc.?

    He will never approach reference level, and $ are relatively not an issue. I was thinking the shivas plus a Crown K1 or K2. There is a (guessing) 250 cu ft store room in the proper location. The room itself will be rather big and open to othe areas of the house somewhat.

    Neither he nor I have a PC (macs, lots of macs) so if you have software suggestions, consider that.

    Whatcha think?

    Brandon
  • JonMarsh
    Mad Max Moderator
    • Aug 2000
    • 15209

    #2
    Hi Brandon,

    The beauty of an IB sub is that it's probably the least design intensive approach to a subwoofer construction - rear room volume is relatively non-critical, and the driver LF response is determined largely by the driver free air Qts.

    In addition to the Shiva 12" from Adire, the DPL 12 (designed for Dipole applications) could work very well.

    The "trickiest" part or main decision to make is how high you want to run the sub to crossover to your main system. If you use a manifold array, as Thomas has done, the phase shift due to time difference between the drivers fartherest down the mainfold and those near the exit will affect the frequency response above 80 Hz, causing some roll off. If you have the room for a flat panel array, this will produce the flattest upper bass response, and allow using 100 Hz or higher crossover without any HF EQ on the sub array.

    Check out Thomas's project info on the Klone Audio site.

    Best regards,

    Jon




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    Comment

    • ThomasW
      Moderator Emeritus
      • Aug 2000
      • 10934

      #3
      Brandon

      Yeap you can't really model an IB that's in a manifold array. So don't worry about software. You can model it a bit if you simply use a HUGE seal box design 10+X Vas of the sum of the drivers.

      Some IB guiide lines are......

      Keep the array 'short', one driver in height. That way you'll help eliminate the cancellation Jon talks about. This means using a box about 15" OD on a side for 12" drivers, or 17"-18" OD on a side for 15" drivers. With a comensorate ID opening for the opening into the room

      Have more driver displacement than you think you'll need. With a 'typical' box sub the maximium output is limited by the thermal resistance of the VC, (in otherwords they get hot and melt if you exceed the recommended power). With an IB you're excursion limited by the driver's suspension long before you reach thermal limit of the VC. A good example of this is the new IB woofer from PE. It has a thermal limit of 350 watts, but they de-rate that to 140 watts due to the excursion limit of the driver.

      A great IB would be one using new PE IB woofer since it's offered at $100ea in 2+ quantity. 4 of these mounted in a 17-18" OD cube would be a killer IB for $400

      PE IB woofer

      Finally IB's don't require big amps. A Crown K1 would easily drive any IB to very high SPLs'




      theAudioWorx
      Klone-Audio

      IB subwoofer FAQ page


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      Comment

      • Brandon B
        Super Senior Member
        • Jun 2001
        • 2193

        #4
        Thanks guys. Pretty much covers everything I needed to know.

        BB

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