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ATTENTION DIY CAB BUILDERS!!

Discussion in 'Amps and Cabs [BG]' started by rumblinbass, May 5, 2004.


  1. rumblinbass

    rumblinbass

    Aug 22, 2003
    Wimberley, TX
    I am curious to find out how to calculate vent dimensions for a cab that I am building. I have a couple of books that have tables that list ports but I would prefer vents. Does anyone know how to do this or know of any books that explain this?
     
  2. ESP-LTD

    ESP-LTD

    Sep 9, 2001
    Idaho
    The sound/pressure is only concerned with the port volume and length. Figure out those specs for a round port, and then make a port whatever shape makes you smile. Keep in mind those formula's will get you close, but it still requires hand tuning to get it just right, and vents are harder to adjust than round ports.
     
  3. country_boy

    country_boy

    Apr 13, 2004
    Houghton, MI
    There are some good online calculators <a href="http://www.carstereo.com/help/Articles.cfm"> here </a>. Used the port dimensions calculator for my hifi speakers and they sound very nice.
     
  4. geshel

    geshel

    Oct 2, 2001
    Seattle
    Fixed it for you. :)
     
  5. rumblinbass

    rumblinbass

    Aug 22, 2003
    Wimberley, TX

    I hear ya! I understand what you are saying but it's just not adding up. A rep from Eminence is telling me one thing, and a book that I have is telling two different things. I figured that they would add up to about the same volume...but they don't. I'm just trying to get an idea of what's going on.
     
  6. ESP-LTD

    ESP-LTD

    Sep 9, 2001
    Idaho
    Appreciated :)
     
  7. geshel

    geshel

    Oct 2, 2001
    Seattle
    They might tell you different things because there are many different possible tuning frequencies you might choose.

    And, even if they tell you the same tuning frequency, the volumes might not match. It is counter-intuitive: if you make the area of the port bigger, you have to make it longer as well! to tune to the same frequency.
     
  8. Trevorus

    Trevorus

    Oct 18, 2002
    Urbana, IL
    Actually, It wouldn't be hard if you use that thin 1/4" plywood called luaun. You just cut a bunch of pieces to shape, and tune your vents by putting them in the floor of the cabinet for a square bottom or top vent. if you find one that works, you can smooth the edge it leaves (if you don't build it to the back wall of the cabinets) with durham's rock hard water putty to remove any air turbulence.
     
  9. Nightbass

    Nightbass

    May 1, 2001
    Seattle, WA
    If the front or back of your box is 3/4", then you treat a vent as a port with a length of 3/4". In the end, a little hand tuning may be necessary.

    Have you downloaded and tried out WinISD from http://www.linearteam.dk ? It's the perfect tool for what you're trying to do.

    Nightbass
     
  10. country_boy

    country_boy

    Apr 13, 2004
    Houghton, MI
    You could also use a piece of wood to lengthen this dimension (like a shelf) if it makes it easier to tune or makes the dimensions more convient. Also remember that using the one of the sides of the cab for a side of the port increase its effective length.
     
  11. rumblinbass

    rumblinbass

    Aug 22, 2003
    Wimberley, TX

    No, I haven't used any software. I have given it some thought but just haven't done anything about it.