Bracing for a sealed sub

Discussion in 'Archived Threads 2001-2004' started by FredV, Jan 25, 2003.

  1. FredV

    FredV Agent

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    Does a sealed sub box require more internal bracing than a vented one, all other thingas being equal?
     
  2. FredV

    FredV Agent

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    Intuitively, it would seem that vented (and PR-equipped) speakers would have a "pressure-relief" outlet, whereas sealed boxes don't. Therefore, if all else were equal, internal pressures would seem to be more with sealed designs. If this were not the case, I'd be curious to know why.
     
  3. Jack Gilvey

    Jack Gilvey Producer

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  4. Richard Greene

    Richard Greene Stunt Coordinator

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    Sealed enclosures need less bracing than ported enclosures because the stuffing inside the enclosure absorbs some energy. A fully stuffed sealed enclosure requires 1.25 to 1.75lbs. polyester stuffing per cubic foot (or 1lb. fiberglass per cubic foot). 0.5lbs. polyester stuffing per cubic foot is not dense enough to absorb a lot of bass energy.

    Stuffing located in the center of the enclosure absorbs the most energy. Stuffing on a wall doesn't absorb that well. That's why lining a ported subwoofer enclosure with fiberglass does little to absorb frequencies below 100Hz.

    http://www.integracaraudio.com/carau...ces/fiberfill/
     
  5. Andrew Testa

    Andrew Testa Second Unit

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    Richard,

    That URL is very interesting, and seems to contradict the stuffing tests in Dickason's Loudpeaker Design Cookbook. He claimed finding the lowest Qtc in a sealed box using a 50/50 combination of 4 lbs/cu. ft. and 2 lbs/cu. ft. of fiberglass. That's a much heavier fill that Nousaine used. Granted, Dickason was testing a small box, but it was in line with Tom's smaller box. Does anyone have any insight into why there might be a discrepancy? Should I email Tom and just ask his opinion?

    Andy
     

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