(Car sub question) Is it possible...

Discussion in 'OT Technology' started by Mister Mac', Jan 12, 2003.

  1. Mister Mac'

    Mister Mac' Av: Daniela Denby-Ashe in Torchwood S1Ep7

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    I should know the answer to this :o, but anyway... Is it possible to have a box with subs on opposite sides? Like one on the front and one on the back? How about for a ported box, with port/s on one side only? :confused:

    Thanks :o
     
  2. flynfrog

    flynfrog Cool isnt Cheap

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    yes

    one has to be out of phase

    the box jsut kinda acts lieka spring it dosent care what direction the sub is going
     
  3. Mister Mac'

    Mister Mac' Av: Daniela Denby-Ashe in Torchwood S1Ep7

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    Fair enough :)

    What angle? 90°?
    180 would cancel completely, wouldn't it? :confused: Or would it... Time for a few experiments! :big grin:
     
  4. flynfrog

    flynfrog Cool isnt Cheap

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    180 jsut swtich the + and - on one sub

    sine its fliped 180 is corect
     
  5. Mister Mac'

    Mister Mac' Av: Daniela Denby-Ashe in Torchwood S1Ep7

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    :cool: :bigthumb: Thanks for your help!
     
  6. flynfrog

    flynfrog Cool isnt Cheap

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  7. 04

    04 Guest

    If you are talking about putting woofers on either side of the box, they will not be out of phase at all frequencies. Only at higher frequencies. If you wire their polarity 180degrees different, you will get more cancellation. I would keep the polarity the same unless you try it and it sounds better the other way. My guess is that you will not want to reverse the polarity, but try it both ways to be sure.
     
  8. flynfrog

    flynfrog Cool isnt Cheap

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    care to explain why

    ??

    if the polarity is the same wont one be moving the exact opostie of the other and if there is no divider in the box he will def lose out put

    jsut curious
     
  9. 04

    04 Guest

    Because the wavelength in the passband will not be 180 degrees out of phase, since they are relatively close together. If you had one subwoofer on one end of the car, and one at the other, then yes, it would be more of a concern.

    However, that does seem to make sense that putting the woofers on opposite sides would cause a cancellation, because you are right, they are facing opposite each other. Hopefully Mister Mac will build the box and try it both ways so we can see which method is correct.
     
  10. flynfrog

    flynfrog Cool isnt Cheap

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    i dont think they are on opsite sides of the car though
    i think he means with them on the same plane with one fliped there for it would be 180 out of phase

    also waht if they are sharing the same air space

    sorry im just not picturing it

    make a paint drawing
     
  11. 04

    04 Guest

    [​IMG]

    I am thinking he is refering to #1

    Yours is #2

    So, number two most certainly should be wired opposite polarilty.

    #1 is hard to decide, he will need to experiment.
     
  12. flynfrog

    flynfrog Cool isnt Cheap

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    i think he means #2 since he wants to show the magnet

    number 1 would be both of them the samei think
     
  13. flynfrog

    flynfrog Cool isnt Cheap

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    and your paint drwaing far supirior to mine

    although mine was 3d
     
  14. Mister Mac'

    Mister Mac' Av: Daniela Denby-Ashe in Torchwood S1Ep7

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    I tried a small cardboard :o test box wit a pair of old 6" drivers, but I couldn't really make any conclusions because the box leaked so much :rofl:

    Unfortunately I don't have enough time or MDF to make a proper box :( I'm going to try something with another box I have though... I hope I haven't sealed it up too well :big grin: (So I can pull it to bits again)

    I DID notice that BOTH setups (same phase/opposite phase) were louder than a single sub, but, again I couldn't tell for sure :( The opposite-phase setup seemed to sound DEEPER than same-phase, probably because it's a semi-isobaric setup :)

    IF I can do a test and I'm happy with the results, I MAY be building a full-size box for my car with 4x 12"s, with all magnets facing the back of the car, like this:

    Code:
    (Top View)
    Front                Back
           _________
           |\ _    |\ _
           | |[u] [/u]|   | |[u] [/u]|
           |/      |/
           |       |
           |       |
           |\ _    |\ _
           | |[u] [/u]|   | |[u] [/u]|
           [u]|/      |[/u]/
    
    
    
     
  15. Mister Mac'

    Mister Mac' Av: Daniela Denby-Ashe in Torchwood S1Ep7

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    Correct :)
     
  16. Mister Mac'

    Mister Mac' Av: Daniela Denby-Ashe in Torchwood S1Ep7

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    Here's the box I'm going to test it with

    It contains 2x 10"s in a bandpass config, about 3.3 cu.ft total. I'm going to attempt to remove the end panels and swap the sub connections around :ugh2: More pics to come soon as I work on it...

    [​IMG]
     
  17. Mister Mac'

    Mister Mac' Av: Daniela Denby-Ashe in Torchwood S1Ep7

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    My newly converted test box :bigthumb:
    [​IMG]

    Nuclear-proof porthole cover
    [​IMG]

    Note that the box is 100% airtight :p
    [​IMG]

    My fan-cooled 500 Gigawatt test amp :cool: :big grin:

    [​IMG]
     
  18. Mister Mac'

    Mister Mac' Av: Daniela Denby-Ashe in Torchwood S1Ep7

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    I did a few tests at different frequencies.

    CONCLUSION: The connections must be swapped on one sub, or it won't work. As for output, I'd say it's pretty close to the same as having the subs in the same plane :cool:

    Of course, having all the subs facing the same way, like in my diagram above, the connections would all be standard, noi swapping needed :)

    The only problem is, one side of the box gets negative bass, but that won't matter too much in my application.

    Next question: Is 3 cu.ft enough for 4 average-range 12"s?

    :big grin:
     
  19. Mister Mac'

    Mister Mac' Av: Daniela Denby-Ashe in Torchwood S1Ep7

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    Oh, and BTW, to answer my own question about ports: Ports are useless in this setup because the air pressure inside the box is constant :big grin:

    edit: Only problem is, that means it's infinite baffle, correct? :sad2:
     
    Last edited: Jan 16, 2003
  20. Mister Mac'

    Mister Mac' Av: Daniela Denby-Ashe in Torchwood S1Ep7

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    One problem that's hopefully related to the box itself: Below 40Hz it sounds awful :sad2: Heaps of interference between the subs :(

    I'll try putting some damping material in and see what happens :)

    edit: :doh: I forgot I had an inductive LPF connected in series with the subs. That's out now, and everything's beautiful! :bigthumb: :cool: :bowdown:

    edit2: Still a slight bit of interference below 20Hz, but pretty good considering the subs are worth $15 USD each... :rofl:
     
    Last edited: Jan 16, 2003
  21. 04

    04 Guest

    If you are talking about your bandpass box, you have to have a port....

    I cant think of any situation other than a true infinite baffle setup where the port wouldnt do anything....

    Your box is too small to be infinite baffle.
     
  22. 04

    04 Guest

    Yup, you gotta realize that a sub is highly reactive. At its free air resonance, it has an extreme reactance peak. Putting passive xover components such as capacitors and inductors will not work well at all in that frequency region, because of this extreme reactance, and they will be affected.

    What do you mean by you get interferarnce below 20hz? What is the tuning frequency of the box?

    Also, you said you wanted to make a 3cuft box for your subs? What type of box? Without knowing the electromechanical properties of the speaker, it is very hard to guess the appropriate size....
     
  23. flynfrog

    flynfrog Cool isnt Cheap

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    whats os wrong wiht a plain sealed box :duno:
     
  24. 04

    04 Guest

    nothing wrong with a plain sealed box. Less output that a vented or bandpass one though probably.... Depends...
     
  25. flynfrog

    flynfrog Cool isnt Cheap

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    a good sealed box is better than a rigged up every thing else
     

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