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Reload Thread: NEW BUILD IDEA, need help with port dimensions :)

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    Moble Enclosurs is offline Box Designer/Builder



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    Re: NEW BUILD IDEA, need help with port dimensions :)

    Quote Originally Posted by akheathen View Post
    oh, tripple wowee..... first, i need to start making sure there is not another page before posting, lol, 2nd, i can't belive i read that right. mobile measured the port from the outside, not the centerline?!?!?!?, and 3rd, you went way backwards on that port area. that is only 7.3"^2 per cu, which is absolutely tiny.... like those truck boxes that had the tiny 1.5" round ports in them or even bigger prefabs back inthe day, the ports really did nothing.......... and yours will be highly inefficient and barely effective. at lower power levels, say 300watts, the port will have an effect, but with some ral power, not so much. if you hadn't already glassed it, i would suggest putting it in raw, with just sealant and seeing how you like it. then, when it doesn't reall have the output you expected, then add 1.5-2" width to the port and it will be more than you hoped for.... your tuning and volume #'s were just about spot on, so you are doing good there, just remember lenght of the port is measured down the centerrline of the port, and port displacement also includes 1/2 width of the port beyond.....

    Another remark without understanding acoustics........I love it. Yes, most of the audio community will measure centerline, but this completely disregards the high pressure at the bend, therefore without using 45s to control the propagation of the wave, the high pressure area HAS TO BE COUNTED!! The measurement was not exterior, it subtracted the thickness of the wood. . If he were to put 45s in the line, then yes, a centerline measurement would be recommended. You cannot disregard the portion that causes the most effect in the output in terms of nulls and peaks. A lot of people do not know HOW to account for this, so they go simple.

    Do you understand now?





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  2. #32
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    Re: NEW BUILD IDEA, need help with port dimensions :)

    Quote Originally Posted by akheathen View Post
    oh, tripple wowee..... first, i need to start making sure there is not another page before posting, lol, 2nd, i can't belive i read that right. mobile measured the port from the outside, not the centerline?!?!?!?, and 3rd, you went way backwards on that port area. that is only 7.3"^2 per cu, which is absolutely tiny.... like those truck boxes that had the tiny 1.5" round ports in them or even bigger prefabs back inthe day, the ports really did nothing.......... and yours will be highly inefficient and barely effective. at lower power levels, say 300watts, the port will have an effect, but with some ral power, not so much. if you hadn't already glassed it, i would suggest putting it in raw, with just sealant and seeing how you like it. then, when it doesn't reall have the output you expected, then add 1.5-2" width to the port and it will be more than you hoped for.... your tuning and volume #'s were just about spot on, so you are doing good there, just remember lenght of the port is measured down the centerrline of the port, and port displacement also includes 1/2 width of the port beyond.....

    Also, it has to be added that measuring port area by "per cubic ft" is very inaccurate. It does not account for all parameters in calculating for minimal port noise or coupling. People need to get away from this common misconception of port area. Just because a port is smaller than you like, does not mean it is ineffective. In this design, you may be right or wrong, I do not know as I have not personally designed it myself, but again, to assume it's too small based on basic area needs is like saying the small ice cream cone is too small to hold more than 3 scoops....which has been proven incorrect as well, lol. But in this case, port area is less physical, and more acoustical. You can't say, "it's too small" without knowing how it was calculated or what it was calculated for.





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  3. #33
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    akheathen is offline trianoacitol contraceptiv akheathen is a Supporting Member of the forum!



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    Re: NEW BUILD IDEA, need help with port dimensions :)

    lol, um... ok



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