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    #1AlpineFan's Avatar
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    Resonant Frequency and more

    so to find the resonant frequency of a car. get a spl meter like the one at radio shack. play pink noise and turn it up to you get like 100db. then play frequency tracks and watch the meter to see the highest db at the same volume. Correct?

    So if i do that before a put a wall in, would the RF still be the same? I would think that it would change but I've never done this so i have no experience with it.

    Then once i have the RF. I need to make the box so that its tuned for the same frequency to get the highest spl with whatever subs and in that car. correct?
    If this is the case, the only thing you need to look for in subs spl wise is power handling? Correct?
    Why would you care about anything else(sub wise)?


    Teach me oh wise ones!

    Sorry if this is confusing.







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    dbhittin's Avatar
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    im almost positive u tune your box 7hertz below so that it peaks at the RF of your car




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    can someone explain why 7 hz.




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    you bastards are no help. lol




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    Re: Resonant Frequency and more

    play with winISD and it'll be self-explanatory.

    People who compete with walls, some of em do away with the RF business, just use as high a tone as the rules allow, then calculate ports according to that.



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    winisd says i need to make a box 21.4 ft3. and a port thats not even an inch in diameter. tuned at 19.77 hz.

    Yeah its pretty self explanitory alright. don't use winisd.

    I have no idea what is wrong or how to work it. i just put the values in and thats what it comes up with.

    anybody have links on how to make it work more sanely.




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    Re: Resonant Frequency and more

    Quote Originally Posted by #1AlpineFan
    winisd says i need to make a box 21.4 ft3. and a port thats not even an inch in diameter. tuned at 19.77 hz.

    Yeah its pretty self explanitory alright. don't use winisd.

    I have no idea what is wrong or how to work it. i just put the values in and thats what it comes up with.

    anybody have links on how to make it work more sanely.

    Well, you're supposed to change those numbers according to what you have...

    When people say don't use winISD< it's cause people look at the colorful graphs and think they know what they're seeing. I sure don't, but it's a nice comparsion to see what size boxes would do what with the same subs. ALso, you can use it to identify which point the sub will go over xmax (hence figuring out the point the SSF should be)

    Also, let's say you put in about 4 cubes at 40Hz. It'll be easy to see which freq the box generates the most dB's. Tune the box in such a way that the peak or ripple tallies with your resonant frequency. There you go, more SPL.



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    I put in the number's that are listed for my sub and thats what it said.
    What do i need to change to get it right?

    isn't 20 hz pretty low for spl. don't i want it up in the 40's




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    If you type in something like 10cu' (or what ever box size you have) and 42Hz (or what ever freq. you want) it will give you a port length. If your trying to figure out the size of the box, just type something in and keep changing it until you get what you want. You can also decide how wide and tall you want the port. What I would do is build a box that's size would give me the largest port area...and have it's peak match up with you RF.



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    **R = sq.rt. A / Pi (for square/slot port)

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    Re: Resonant Frequency and more

    Quote Originally Posted by Trixter
    If you type in something like 10cu' (or what ever box size you have) and 42Hz (or what ever freq. you want) it will give you a port length. If your trying to figure out the size of the box, just type something in and keep changing it until you get what you want. You can also decide how wide and tall you want the port. What I would do is build a box that's size would give me the largest port area...and have it's peak match up with you RF.
    werd, trix knows what he is talking about. AND, i got that box built today in 2.5 hours....WORLDS of help from my neighbor that owns an entire pattern making shop (table saws, sander, the WORKS) he made EXACT cuts and we glued that **** together in no time....pics will come soon...it looks great. peace

    NG




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