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  1. #1
    Join Date
    Dec 2009
    Posts
    236

    Default Lets Help Build a 4th Order Bandpass Sub Box!

    Hey Everyone!

    One of the loyal Sonic Facebook fans is building a 4th order bandpass box for his subs and is looking for some help and advice! We know that many of our forum members have a lot of experience with building boxes. Can you help him out with some advice and suggestions?

    Thanks! Below is what he is looking for.

    "hihi, im probably gonna be building a different box for my subs. its not moving any air or building up pressure. i was wondering if you or someone could help me double check the design of the new box. it's gonna be a fourth order bandpass.

    My New Box Design

    outer dimensions are 59.5 depth. 33 height. 37.5 width
    16 subs total.
    qts - .46
    Vas - 2.83 ft^3
    Fs - 25

    the sealed area will be 7.93871 per 8 subs. so Vr - 15.87742 cubic feet
    ported area. Vf - 17.88276 cubic feet.
    ported area tuning. Fb - 45. port will be 19.5x19.5. 3 inches deep.

    im gonna do removable/interchangeable ports so i can play with tuning if i don't like the sound.

    my first attempt at a 4th order so i really wanna get it right on the first try. dont wanna have to rebuild like my clamshell lol.

    thanks!!!"

  2. #2
    Join Date
    Dec 2010
    Posts
    71

    Default

    hello!! thanks for making this thread for me!

    the subs are infinity 1262w's.
    the box specs are the absolute max i can squeeze out of my 4runner

    my first setup of 4 L7s
    http://www.youtube.com/watch?v=1SVvq76r-u8

    followed up almost immediately by the clam i currently have
    http://www.youtube.com/watch?v=MKmNO09hG6Q

    the clam gets quite a bit louder than the l7s and will hit all the lows. flex is pretty insane on full tilt (video was around 3/4 volume, cant go full tilt at idle). however there is no air being moved and very little pressure buildup (less than the l7s). this is unacceptable considering the cone area and power i have. the 4 l7 12's hit a 148.6 @ 37 hertz with the box and port both being too big and very little tuning or tweaking.

    little background on system.
    the amp is a sundown saz3500@.5 which should produce over 4k. i know the subs can take more but money won't allow for upgrades as of now. my electrical is a dc power 270xp and 3 xs power d3100s. power/ground/big 3 is done in 3/0. back battery has a 3/0 and a 1/0 ground. all terminals were stripped of paint. currently my kicker 850.4 isn't setup (want a finalized sub box before i put mids and highs in and wall). it will power 4 phoenix gold 6x9s and 3.25" tweeters. im going to replace the factory speakers soon and just run them off the head unit.

    it's about that time of year where schoolwork really kicks in, so the majority of the build will probably happen in late december/early january. i think i have everything covered. if theres any other info needed please ask. once again, thanks all!!

  3. #3
    Join Date
    Dec 2010
    Posts
    71

    Default

    one more thing i want to mention. im fairly new to car audio and have 0 experience with 4th orders. all credit goes to 2000LaDe on SMD for the design this 4th order. he said the ratio of ported to sealed should be around 2:1, something i simply do not have room for, but said this should work. hes the one with 48 sa-10s in his truck running off 12 saz-1500s.

    this is his setup.
    http://www.youtube.com/watch?v=Urq96xFDqNw

  4. #4
    Join Date
    Dec 2010
    Posts
    71

    Default

    found this design as well on smd

    someone was going to do 16 12's as well but ended up not.
    this was what he was planning on doing

    1.25c sealed chamber
    1cf ported chamber
    25sqin of port
    16.75" long

    Just multiply that for the amount of subs.

    So in this case it was:

    20 cubes sealed
    16cubes ported
    400 sq in of port
    16.75" long

    im barely short on volume requirements but it'd be very close.

    unless someone tells me otherwise, im still planning on building the box designed by 2000LaDe. he has proof of an insane 4th order and ive read most people doing 4th orders do more ported than sealed.

    infinity recommends 1.25 sealed for the subs but with what im doing it will be 1 sealed. will that be a big issue? polyfil maybe?

  5. #5
    Join Date
    Dec 2010
    Posts
    71

    Default

    also this is for my daily driver...well only driver lol. don't care about metering high or burps. what i do care about is hitting the low lows and moving lots of air. ground pounder!!!!! i listen to a lot of hip hop/rap and some chopped/screwed/slowed songs. wanna hit the looowwwssss. hopefully it will play fairly flat from 20s to 50-60s. i'm downloading a couple box modeling programs right now, dont know how well they work though. i feel like i'm talking to myself o.O lol.

  6. #6
    Join Date
    Dec 2010
    Posts
    71

    Default

    dled winisd. modeling the box. anyone know how reliable this program is for 4th orders?

    i modeled it to 2000LaDe's design. only discrepancy is the port length. winisd says it for a 19.5x19.5 port tuned to 45 the port needs to be 13.5 inches long. the gain graph goes something like this. peaks at 35-37. db gain from 30-31 up to around 57-58. i listen to almost all hiphop/rap/r&b. need looowwwwwsssss. this is for my daily/only driver. no interest in metering high or burping. going for groundpounderrrrr!!! so maybe tune lower? dont remember the term but the -3 db drop is at 27ish and 67 ish

    anyone wanna help me figure out wtf im doing? lol =D

    winisd 45hz tuning





    winisd 42hz tuning





    sooo now i don't know what to do to figure this out myself lol. i'll continue my stupid amounts of googling/research/reading and see if i can understand these things better.

  7. #7
    Join Date
    Dec 2010
    Posts
    71

    Default

    anyone?....
    btw i dont think the graphs/models i posted account for port displacement. ill model em up again and re-post.

  8. #8
    Join Date
    Dec 2010
    Posts
    71

    Default

    did some quick remodeling accounting for port displacement and came up with this. with the port being 19x19. 12.5 inches long. after port displacement it comes up to being tuned around 48.

    F3(L)- 28 hz
    F3(H)- 83.4 hz

    the ported to sealed ratio is pretty much 1:1.

    i'm definitely not going to be able to do any work on this until early january. my plan is to build it to the specs listed. port will be 19x19. 361 sqin of port area. then just do tweaking with the port length until i find a tuning i like.

  9. #9
    Join Date
    Dec 2010
    Posts
    71

    Default

    one more thing. the area for the ported figures for double baffling the loading wall. if i do single baffle it will add 0.47852 ft^3 to the ported area. think i may do a single baffle and then just find a way to reinforce the loading wall.

    *edit - would make Vf 18.36128 cuft before port displacement
    Last edited by irpirate; 12-07-2010 at 11:52 PM.

  10. #10
    Join Date
    Dec 2010
    Posts
    71

    Default

    last post before i call it quits for today. think i'm going to start with 45.5 tuning. 19x19 port 15 inches long
    vf - 15.9
    vr - 15.877
    f3(l) - 27
    f3(h) - 78.5
    peaks at 36 hz

    this is all winisd modeling and i have no idea how its going to sound walled at the b pillar.

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