Pair of Dual opposed 12"s.Thoughts please !

Discussion in 'DIY Speaker & Subwoofer Building' started by jason shep, Feb 23, 2014.

  1. jason shep

    jason shep
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    Hi all,
    I'm thinking about making a pair of subs with dual opposed 12" drivers,I know a pair of single 15"s would be much better value but I like the very clean,force cancelling effect of dual opposed.

    Could any of you guys give me some ideas on box sizes please,as compact as possible would be good,I'm looking for max performance from around 120hz to 20hz,any sub 20hz can come from room gain,I don't want to chase that in the design of the sub,impact & clean bass are the priority.

    I have an IN-6000DSP already,probably go with FI Q drivers but I'm open to other suggestions.

    Thanks guys :lease:
     
  2. KelvinS1965

    KelvinS1965
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    I can't help directly, but only to say that I'll be very interested in how this works out for you. As you may know I've built (or I should say 'assembled') a pair of Q15 subs myself which I'm very pleased with, giving a very clean bass sound compared to the single Monolith I used previously.

    I'm not sure how you go about modelling for the dual opposed set up though? I had a quick play with Win ISD to see what the benefits might be, but only had the option to chose isobaric or 'normal', so I'm not sure where it 'puts' the subs if you chose 2 drivers and 'normal'. I compared a single Q15 to a pair of Q15 in isobaric set up and there is much less driver excursion for the same input, though 3dB less output across the range. That's with them both set to 1500 watts input, but of course you could put 1500 watts into each speaker in the isobaric mode, if you used both channels on the NU6000DSP, which gives you back the 3dB (according to Win ISD), but the cone excursion is still half what the single would be so the distortion would be less too I imagine.

    With the opposed drivers is this supposed to cancel out more distortion? The overall output would be more with two separate single boxes, but then that takes more physical space too...as I said I'm interested in how this works out.
     
  3. jason shep

    jason shep
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    Hi Kelvin,yes the idea is separate subs,each sub with 2 drivers on opposite sides of the boxes.
    My friend "forum member Ashman" has a pair of Fi Q15" dual opposed and they are superb,I'm after a similar sound in smaller cabinets.
     
  4. scottthehat

    scottthehat
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    jason if you have the budget for fi q then why not 2x dual 15 if you have the room, 120l cabs would make them sing and an nu6000 to run both, this is what ashman on the forum has.
    22" cubes with double front and rear or sides(baffle) dependednt on how you position them, with some bracing will give you 120l easy.
     
  5. jason shep

    jason shep
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    Thanks Scott,
    I am hoping to sell my house later this year & I plan to rent while I look for my next house to buy,I want something more compact than the 120L cabinets that Ashman has,they sound incredible & I do think 15"s are a bit of a sweet spot in sub driver size/value but just not practical for me at this time,hence why I'm looking to go dual 12"s.
     
  6. scottthehat

    scottthehat
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    if my win is right it says the 12" need about 12l box(please some one else check)

    and if that was right i would aim for a 16" cube which will give about 40l,
    which will give you about the same excursion as the 15" but the performance difference is a fair bit under.
    dual 12"(40l box) at 20hz is 104.5db (a single 15" in a 65l box will just edge that)
    dual 15"(120l box) at 20hz is 109.3
     
  7. jason shep

    jason shep
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    Two Fi Q12"s in 40L ! Really ? That would be great Scott but even a BK xxls400 is 50L with just the one driver !
     
  8. scottthehat

    scottthehat
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    the 15" only really need a 40l so 2x15 would only really need 80l,
     
  9. jason shep

    jason shep
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    Wow,thanks Scott,two 15"s in 80L sounds good to me :cool:
     
  10. scottthehat

    scottthehat
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    if you can do 80l then do that an add load of fill.
     
  11. MemX

    MemX
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    Aren't the SP4s better for smaller boxes? More power handling and all that :)

    If you want really small, do an isobaric design to halve the box size but lose the 3dB of output mentioned above. Would require 8 drivers if you wanted the output of 4, though (ignoring the -3dB thing)...

    Otherwise, D.O. = double the box size of one driver, same as Push-Pull or just front firing non-opposed :)
     
  12. MemX

    MemX
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    Thinking about it, if you had a bit more room you could look at Push Pull Slot Loaded (PPSL) - check out the PPSL thread on DIYAudio forum (the subwoofer section) for some discussion and some photos, they're said to be so clean they sound like servo subs (not that I've heard them myself lol) :)
     
  13. Spock

    Spock
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    2 15s in an 80l cab? That sounds mega. Didn't think they would go in such a small box!
     

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