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1. 

   Calculating Slot port for Irregular Shaped Enclosure

   • stonekutta
   • 4 mo ago
   • General Car Audio Discussion

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   3 mo ago

    by stonekutta
   1. 

      stonekutta

      · Registered

      1987 Chevy Monte carlo LS

      Joined 7 mo ago

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      115 Posts

      Discussion Starter · #36 · 3 mo ago

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      daloudin said:

      The Secondary Resonance between two different ports of the same surface area and length "should" be the same but I've seen some square ports that had some resonance that didn't show up in calculations.
      
      Here's another version of the same enclosure without the folded port 10" x 4.25" x 44.75"...
      View attachment 357616

      Click to expand...

      that is the exact design I was imagining! I was imagining this because it would reduce angles and additional volume loss by using less wood, however this design is the one where I would need to be aware of potential secondary resonances, correct? If I am understanding correctly the 1x 43" port should reduce the chances of secondary resonances. a second question- would 3/4" 3M ThinsulateTM Acoustic/Thermal Insulation AU4002-5 (20' x 60") work for lining the box? I have some that is backed on one side. if so attach it so the white fuzzy is facing the inside of the enclosure? Thanks again for all the hard work! it is appreciated!

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   2. 

      daloudin

      · Super Moderator

      2012 Jeep Grand Cherokee Overland 5.7 Hemi

      Joined Nov 2, 2020

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      2,921 Posts

      #38 · 3 mo ago

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      stonekutta said:

      that is the exact design I was imagining! I was imagining this because it would reduce angles and additional volume loss by using less wood, however this design is the one where I would need to be aware of potential secondary resonances, correct? If I am understanding correctly the 1x 43" port should reduce the chances of secondary resonances. a second question- would 3/4" 3M ThinsulateTM Acoustic/Thermal Insulation AU4002-5 (20' x 60") work for lining the box? I have some that is backed on one side. if so attach it so the white fuzzy is facing the inside of the enclosure? Thanks again for all the hard work! it is appreciated!

      Click to expand...

      stonekutta said:

      that is the exact design I was imagining! I was imagining this because it would reduce angles and additional volume loss by using less wood, however this design is the one where I would need to be aware of potential secondary resonances, correct? If I am understanding correctly the 1x 43" port should reduce the chances of secondary resonances. a second question- would 3/4" 3M ThinsulateTM Acoustic/Thermal Insulation AU4002-5 (20' x 60") work for lining the box? I have some that is backed on one side. if so attach it so the white fuzzy is facing the inside of the enclosure? Thanks again for all the hard work! it is appreciated!

      Click to expand...

      As long as the port is not square (or nearly square) then you run less risk for secondary resonance. The perfect square is the worst case scenario.
      
      The 2nd version would be easier from the perspective of less material but more difficult from a glue up since the side with that port has less support and spanning the channel on the bottom gets complicated to cut accurately. But either one is doable if you can make accurate cuts.
      
      See the attached PDF. Thinsulate loses effectiveness below about 1,000 Hz pretty dramatically. It's light weight is the opposite of what you want in a subwoofer enclosure. Rockwool, polyester batting or fiberglass duct board are better. View attachment 3mtm-thinsulatetm-acoustic-insulation.pdf
      
      Sent from my SM-G965U using Tapatalk

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