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    would someone wanna help me with this one?

    i am doing the formula wrong for calculating the length of a port. Maybe i **** at math, but i would appriciate it if someone could plug these numbers in and let me know.

    (Av) Port size: (H) 12 inches, (W) 1.25 inches
    (Vb) Box Net Volume: 1.75 ft. 3 (21 inches cubed)
    (Fb) Tuning Frequency: 32 Hz

    I know this is rediculous to ask someone on here to do this for me, but i must be doing something wrong cause im getting like 600 for my port length, and i just wanted to see if there was someone out there that was a whiz at this and could do it real quick or somethin.

    Thank you to anyone who looks this over or atttempts the help me figure this out.
    I appriciate it.



    HU: alpine CDE-9843

    SUBS: 3 12" MTX thunder 5500s

    AMP: memphis PRD1000.1

    MIDS: 2 4" poineers, 2 6x9 dub series


    the 3 commandments

    1)dont hunt...... outta season
    2)dont use lords name in vain..... in church
    3)dont commit adultry....when the wife is in the area code.




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    Re: would someone wanna help me with this one?

    Quote Originally Posted by bigdub_diesel
    i am doing the formula wrong for calculating the length of a port. Maybe i **** at math, but i would appriciate it if someone could plug these numbers in and let me know.

    (Av) Port size: (H) 12 inches, (W) 1.25 inches
    (Vb) Box Net Volume: 1.75 ft. 3 (21 inches cubed)
    (Fb) Tuning Frequency: 32 Hz

    I know this is rediculous to ask someone on here to do this for me, but i must be doing something wrong cause im getting like 600 for my port length, and i just wanted to see if there was someone out there that was a whiz at this and could do it real quick or somethin.

    Thank you to anyone who looks this over or atttempts the help me figure this out.
    I appriciate it.
    I'm not a box calc, so Im not much help What is the box for? where did 21 in.^3 come from?



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    Re: would someone wanna help me with this one?

    not sure, it said on jls site that the net volume needed to be in cubic inches, or at least i thought it did. i know this is stupid, but i figure ill throw it out, and maybe some one can do it



    HU: alpine CDE-9843

    SUBS: 3 12" MTX thunder 5500s

    AMP: memphis PRD1000.1

    MIDS: 2 4" poineers, 2 6x9 dub series


    the 3 commandments

    1)dont hunt...... outta season
    2)dont use lords name in vain..... in church
    3)dont commit adultry....when the wife is in the area code.

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    Re: would someone wanna help me with this one?

    For a 1.75 cubic foot enclosure I get right around19.35" for the port length. With that size box though, I'd up the port area from 15 sq inches to 25-30ish to avoid port noise and increase output a bit. You would increase the port length to ~40.5" for that size box with a port area of 30 square inches.

    EDIT: for the record 1.75 cubic feet is 3024 cubic inches, which is probably where you went wrong.



    Fuc, how come when I copy and paste **** it never gives me the cool blue thing in my sig. Sonofa*****withhotredtabascosauceonmynutz!!!!!
    References: g30ffr3y,Cjjackson85,Pearldrummer, Rattlebrain, Harrison486, excelerater, ax600, XtrmAudioCncpts

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    Re: would someone wanna help me with this one?

    thanks a lot for doing that. Im actually planning on making 2 sep chambers 1.75 cubic feet each, and putting a port in each one. This is my first ported box, so i wanted to keep it as simple as possible, and not have to zig and zag the port to much, so i figured a one small port for each sub wouldnt be to hard. Im just curious, how did u plug those numbers i gave you into that formula? I was wondering if you could pm me back with that formula with my numbers plugged in so i can do it myself and make sure i get 19 or 20, or whatever it was you figured it to be. then if i need to change my specs i can without posting another thread. I would really appriciate it.



    HU: alpine CDE-9843

    SUBS: 3 12" MTX thunder 5500s

    AMP: memphis PRD1000.1

    MIDS: 2 4" poineers, 2 6x9 dub series


    the 3 commandments

    1)dont hunt...... outta season
    2)dont use lords name in vain..... in church
    3)dont commit adultry....when the wife is in the area code.

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    swimfreak26's Avatar
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    Re: would someone wanna help me with this one?

    Port length = ((Av*(1.84*10^8))/(Bv*1728*(F/0.159)^2))-(0.823*SQRT(Av))

    Where Av is the cross sectional port area in square inches, Bv is the box volume (net) in cubic feet, and F is the tuning frequency.

    In this formula you can use the box size in cubic feet because the conversion is already in place.

    EDIT: I've just got this in excel so I ran your numbers through real quick, but you should come up with the same stuff by hand.



    Fuc, how come when I copy and paste **** it never gives me the cool blue thing in my sig. Sonofa*****withhotredtabascosauceonmynutz!!!!!
    References: g30ffr3y,Cjjackson85,Pearldrummer, Rattlebrain, Harrison486, excelerater, ax600, XtrmAudioCncpts

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    Re: would someone wanna help me with this one?

    thanks a lot, i just ran it and got it.



    HU: alpine CDE-9843

    SUBS: 3 12" MTX thunder 5500s

    AMP: memphis PRD1000.1

    MIDS: 2 4" poineers, 2 6x9 dub series


    the 3 commandments

    1)dont hunt...... outta season
    2)dont use lords name in vain..... in church
    3)dont commit adultry....when the wife is in the area code.

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