car sub enclosure question v.calculate speaker volume

Discussion in 'OT Technology' started by kamikaze, Apr 21, 2008.

  1. kamikaze

    kamikaze Active Member

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    Ok, so I've got the manual for a sub that I'm going to be building an enclosure for and I need to find out the volume of the speaker so I can make the enclosure that much bigger to keep it at 1 cubic foot. I'm not sure what all that stuff in the Thiele-Small Parameters means, so maybe it's in there :dunno:

    Below are from the pdf manual:

    [​IMG]
    [​IMG]

    The sub is a Kaption CL-12D4

    Thanks :wavey:
     
  2. VenomousSVT

    VenomousSVT New Member

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    Re Electrical resistance of voice coil
    Fs Resonant frequency of loudspeaker moving mass (in free air)
    Qes Electrical Q of loudspeaker
    Qms Mechanical Q of loudspeaker
    Qts Total Q of loudspeaker
    Vas Equivalent air volume of moving mass suspension



    VAS
    17.25 l = 0.609177 ft³
     
  3. kamikaze

    kamikaze Active Member

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    Thanks :wavey:
     
  4. VenomousSVT

    VenomousSVT New Member

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    any time
     
  5. GammaRadiation

    GammaRadiation Active Member

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    Vas is the stiffness of the suspension in relation to a certian volume of air.

    Vas is NOT the displacement of the speaker.

    The displacement of the speaker is not listed there. For small 10's and 12's a good rule of thumb is around 0.15-0.2cuft.
     
  6. VenomousSVT

    VenomousSVT New Member

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    it has always been described to me as total displacement of air while at full excursion. However now that its morning and I have had sleep .6ft3 is alot for a typical sub. I am not familiar with the sub though, for all I know they are the size of a jl audio W7 sub. Those are upwards of 1 ft3 of sub volume.
     
  7. kamikaze

    kamikaze Active Member

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    Would I be better off firing off an email to the manufacturer and see if I can get the specs out of them, or is .1 or .2 ft3 going to make that much of a difference?

    Edit: Phoned Kaption, guy there said that the volume of the driver is .05 ft3 and that a volume that small shouldn't make a difference, but that doesn't seem like a whole lot of volume considering the size of the sub :dunno:
     
    Last edited: Apr 21, 2008
  8. twistid

    twistid Banged By Super Models Moderator

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    it looks the volume of a alpine typ-e, and those are like 0.086ft³ front mount irrc.
     
  9. twistid

    twistid Banged By Super Models Moderator

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    wow, that has less volume than a 12" shallow p3.
     
  10. VenomousSVT

    VenomousSVT New Member

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    there is no way the sub is .05ft3.. thats crazy talk.

    that would be a box that is 4"X4"X4"
     
  11. GammaRadiation

    GammaRadiation Active Member

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    That is Vd, not Vas. Vas is a suspension measurement. The larger the Vas the softer the suspension.

    In either case, he isnt asking for the displacement capeability of the sub but rather the total airspace that the sub will take up so he can add excess airspace to the enclosure to get an accurate net volume.
     
  12. kamikaze

    kamikaze Active Member

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    yea, i think he just didn't know so he gave me some BS response :ugh:

    I guess I can get a rough idea by measuring the magnet and stuff, but that's going to be a pain in the ass...
     
  13. GammaRadiation

    GammaRadiation Active Member

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    0.1cuft isnt going to make a big difference. Add 0.15cuft and call it a day. Is it sealed? If so make it a little undersized and try adding stuffing to your liking. :)
     
  14. VenomousSVT

    VenomousSVT New Member

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    gotcha :)
     
  15. VenomousSVT

    VenomousSVT New Member

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    agreed... just build it and try to compensate for sub volume based on common sense... the the bass sounds a little hollow then shove some insulation in the box to slow down the sine wave.
     
  16. kamikaze

    kamikaze Active Member

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    Thanks for the good tips guys. I've made sub boxes before but I've never gone into this much detail. Since it's for a friend i really want it to sound good and not fuck it up.

    What do you guys put in the box, pillow stuffing? I can't imagine fiberglass insulation being good for the driver...
     
    Last edited: Apr 21, 2008
  17. GammaRadiation

    GammaRadiation Active Member

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    Pillow stuffing is cheap and avalable.

    Fiberglass stuffing is actually slightly better. Not only does it not melt if it does somehow work its way into the gap but it has a higher specific heat and resonant frequincy. Really the difference is slim, if any, between the two.

    If you are looking for SQ and it is going to be in a vehicle a good rule of thumb Qts for the system is 0.808. :)
     
  18. kamikaze

    kamikaze Active Member

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    How do i find Qts?

    Sorry for the noob questions, but I'm by no means a professional :o
     
  19. VenomousSVT

    VenomousSVT New Member

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    are you recommending him to set up his Q at .808, or are you telling him thats what it will be?
     
  20. GammaRadiation

    GammaRadiation Active Member

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    reccomending it.

    As for how to find it, WinISD will do it for you if you dont want to learn how to calculate it yourself.
     
  21. VenomousSVT

    VenomousSVT New Member

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    well would you recommend a free air sub setup as well? I helped set up (tune and set up staging) a few cars and every one of them had a 15" sun or a IB setup. Did an image dynamics accord with a carbon fiber rear deck with an ID 12" suspended from it using the entire trunk as a giant enclosure. It had a super nice low note and would flex the doors on the USAC competition disc without booming. SQ sub setups are the coolest sounding shit ever.
     
  22. kamikaze

    kamikaze Active Member

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    Another question, how does the shape of the box going to affect the sound? It's a sealed box, and due to the space requirement and shape of the box, the back of the woofer is going to be about an inch from the back of the box. Does it matter as long as the volume is right?
     
  23. GammaRadiation

    GammaRadiation Active Member

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    IB is an excelent choice if the sub has a high Q and plenty of displacement capeability.
     
  24. GammaRadiation

    GammaRadiation Active Member

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    It wont affect it too much as long as you arent connecting chambers with PVC pipe or something. No lie, I saw someone do it.
     
  25. kamikaze

    kamikaze Active Member

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    lol, no, It's not like that. This is a quick mockup of what I'm thinking that i did in google sketchup.

    [​IMG]

    [​IMG]

    I haven't yet figured out how I"m going to make the round part, probably do 2 mdf rings, support them with dowel and fiberglass it, then screw it to the square part. I know i need more of a lip on the round part for the sub to screw to, but it was a rough drawing to show to the guy I'm doing this for.
     

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