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Assistance with Box Tuning

Discussion in 'Subwoofer Box and Custom Fabrication' started by ericj, Sep 12, 2010.

  1. ericj

    ericj Full Member

    Since there are so many knowledgeable folks out here, I'm hoping you can help me figure out the best port length for my enclosure. :)

    Currently, the box I have is a common enclosure for 3 first series 10W6s with 2 round PVC 3" ports. Total interior volume is around 3.3 cu ft after bracing & displacement (34"l X 16.5"w X 14"h). I realize it's probably not the optimal volume, but it's the largest rectangular box I determined I could fit when I built it. Both the subs & ports fire upward toward the hatch (car is an '95 Eagle Talon). Subs are wired @1ohm and powered by a Crossfire CFA1000D. Definitely an old-school setup I got goin' on here.

    The current tuning is at or around 31Hz. It has very good low-end response, but punchy bass isn't nearly as good as the sealed box they were in before I built this ported box. I'll take the compromise since I usually listed to rap anyway and the ported box plays so much deeper, but from what I've read on here, tuning higher may be better. I'd rather not rebuild the box, so I'm looking for the best port length for the best performance.

    Thanks for your help!
     
    Last edited: Sep 15, 2010
    ericj, Sep 12, 2010
    #1
  2. TheViking

    TheViking Well-Known Member

    could you please post all the T/S parameters for your subs....that would be a big help. I have no info on them myself
     
    TheViking, Sep 12, 2010
    #2
  3. ericj

    ericj Full Member

    ericj, Sep 12, 2010
    #3
  4. TheViking

    TheViking Well-Known Member

    what is the current length of each of your 3 inch ports?
     
    TheViking, Sep 12, 2010
    #4
  5. ericj

    ericj Full Member

    Right now they're about 9.75" each IIRC.
     
    ericj, Sep 12, 2010
    #5
  6. Ranger SVO

    Ranger SVO Full Member

    I just wanna confirm that this is not a divided box, in other words, both woofers share the same air space. If so we have a lot of options. If its divided we have a problem.

    If its not a divided box, First I would want to change to two 4-inch ports. Second, adjust tuning so that we have a +3 to +6 gain in the 40 to 50 Hz range.

    :DHey, Viking, do you even remember how to use BassBox Pro?? After all, you was gone a long time:rolleyes:
     
    Last edited: Sep 12, 2010
    Ranger SVO, Sep 12, 2010
    #6
  7. TheViking

    TheViking Well-Known Member

    Some day, like ranger and the others I will figure out how to post pics of the response curves on here...till then....

    You are in fact real close to the 31 Hz tuning you indicated. Gives a nice roll off at the lowest octaves. The octaves that dont really matter is the issue! LOL

    Here is what I would do...change the tuning to 40Hz. This will be easy. Shorten both vents to 4.25 " in length. This will give a slightly higher -3dB point, but will give rise to the area of bass that will kick you in the gut and rattle your teeth. I am indicating about a 4 decibal increase in output from about 45 Hz on up....tune it at 45 Hz and get another 3 dB of gain from about 50Hz on up...with no serious repercussion on the lowest octaves. Doing this is kind of like doubling your amplifier power....for free
     
    TheViking, Sep 12, 2010
    #7
  8. TheViking

    TheViking Well-Known Member



    LOL been a while! But i think i am getting the hang of it again. Do me a favor...check what i posted above. I beleive it too be accurate
     
    TheViking, Sep 12, 2010
    #8
  9. ericj

    ericj Full Member

    All the subs are in a common (open) enclosure with no dividers. I built it that way since I had little extra room to play with and didn't want to make the volume any smaller than it already was.

    I would need to double check the measurements, but I'm pretty sure that 4" ports wouldn't fit because they would hit the side of the box & the sub cutout.
     
    Last edited: Sep 12, 2010
    ericj, Sep 12, 2010
    #9
  10. TheViking

    TheViking Well-Known Member

    I run the program with all 3 drivers in a common volume.
     
    TheViking, Sep 12, 2010
    #10
  11. ericj

    ericj Full Member

    Thanks for your help, guys! I'll adjust the ports in the next day or so and report back.
     
    ericj, Sep 12, 2010
    #11
  12. Ranger SVO

    Ranger SVO Full Member

    Viking, your specs look the same as mine.

    ericj, the only thing I would do different is change to two 4-inch ports. At tuning frequency the port makes almost all the sound. A little more port size will improve perfomance slighty.

    Can you do two 4- inch ports around 9-inches long each?
     
    Ranger SVO, Sep 12, 2010
    #12
  13. ericj

    ericj Full Member

    Just checked my box. I can fit two 4" ports and 9" depth will be fine and be a few inches from the bottom wall. I'll pick up some PVC pipe in the next couple days to try it out. Thanks again for all your quick, expert advice. :)
     
    ericj, Sep 12, 2010
    #13
  14. ericj

    ericj Full Member

    Alright, today I adjusted the length of the 3" diameter ports to 4.25". DAMN, what a difference! Sh!t was falling off the walls of my garage. I guess you guys do know what you're talking about. Thanks again for the awesome & friendly advice. :D

    Obviously, I'm really happy with the result, but still plan on increasing the port size to 4" diameter someday soon. It's just too big of an after-work project right now.
     
    ericj, Sep 14, 2010
    #14
  15. Ranger SVO

    Ranger SVO Full Member

    We have our days, besides, me and Viking have been doing this a long time.

    Glad you like it.
     
    Ranger SVO, Sep 14, 2010
    #15
  16. TheViking

    TheViking Well-Known Member

    Glad to hear it ericj. always nice to hear back with positive results......some folks think we are too old to know what the hell we are talking about! LOL!
     
    TheViking, Sep 14, 2010
    #16
  17. ericj

    ericj Full Member

    Just wanted to follow-up on this post. Since I had my amp switched out for a replacement while the other one was getting repaired, I had to wire my subs to 4 ohms to match the amp. When I got the amp back today, since I had to re-wire the subs back to 1 ohm, I decided to change out the ports in the box from 3" to 4". Although I was completely happy with how it sounded with the 3" ports, I have to admit that it sounds a hell of a lot louder and deeper now. Thanks for your help with this, Ranger & Viking! :) Great advice!!!
     
    ericj, Oct 14, 2011
    #17
  18. Ranger SVO

    Ranger SVO Full Member

    Thanks for the update, I always wanna know how things work out and you are welcome.

    And if you decide to build a custom box let us know.
     
    Ranger SVO, Oct 15, 2011
    #18