230L Sealed tempest to Ported

Discussion in 'Home Theater Projects' started by Benihana, Jan 16, 2004.

  1. Benihana

    Benihana Stunt Coordinator

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    How much more output will i get if i convert my sealed box to a dual port box?? And what would i tune a 230L box too?? Thanks.
     
  2. Aaron Gilbert

    Aaron Gilbert Second Unit

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    You can get I would say as much as 7-8 dB more at 20 Hz. This is just going off memory, but I have modeled the Tempest more times than I can count. [​IMG] As to what frequency you should tune the box, that's completely your choice. I don't have a Tempest, but a Dayton Quatro 15", which models within a gnat's eyelash of the Tempest, just has less Xmax.

    Anyhow, I have mine in about a 270l enclosure tuned to 11 Hz. Why? I felt the slow rolloff would be complemented by room gain and produce a flatter response than if I designed the box to be flat to 20Hz without room gain. It also pushes the peak port air speed frequency and group delay peak below the audible range, so in terms of sound quality, my box sounds extremely close a sealed version. If you want the most output, you typically tune to the Fs, which I think in this case is 19 or 20Hz, right? If memory serves, 230l is a bit larger than optimum for that woofer, so you may want to tune slightly lower, say 18Hz, or you could end up with a hump in the response around the tuning frequency.

    Aaron Gilbert
     
  3. Ryan Schnacke

    Ryan Schnacke Supporting Actor

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    That's pretty impressive for "just going off memory". I modelled it in WinISD pro and it does look like tuning to 18Hz with a 225L box (assume ~5 liters for the port) does indeed give you a good compromise between output, extension and rolloff. That gains about 3dB at 35Hz and about 5dB at 20Hz over the 230L sealed model.
     
  4. Benihana

    Benihana Stunt Coordinator

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    thats a pretty impressive gain just for porting, does the sound of the woofer change much goin to ported??
     
  5. TimForman

    TimForman Supporting Actor

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    You're discussing something pretty close to the Adire Alignment enclosure for the Tempest. It's a 215 liter enclosure using 2-3" ports and tuned to ~18Hz. Great for HT.
     
  6. Benihana

    Benihana Stunt Coordinator

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    isn't the adire alignment tuned to 15.4hz, which is better that or 18hz?? Is there anything wrong with ported the box on the top of the cabinet instead of on the bottom? Thx. And will those 2 3" ports give off port noise? Thanks.
     
  7. TimForman

    TimForman Supporting Actor

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    Yep, guess my memory is not as good as others. I've not detected any port noise using 2 of the 3" Precision Ports. And no, it doesn't matter if it's ported on top or bottom.
     

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