Tempest vs. DVC 15 enclosure volume differences?

Discussion in 'Archived Threads 2001-2004' started by jeff lam, Apr 3, 2002.

  1. jeff lam

    jeff lam Screenwriter

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    I always heard from you guys that the DVC can be used in a smaller enclosure. does this mean it wouldn't be a direct drop-in replacement for a tempest. I'm just thinking because the DVC's are so cheap today, could I use a tempest design and just use the DVC instead or will I have to come up with a new design?
     
  2. Patrick Sun

    Patrick Sun Moderator
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    That's correct. Each driver does things a little differently, and in the wrong enclosure, might sound less than optimal. You should run the numbers (preliminarily) in WinISD or Unibox, Adire's LspCAD, and see what's the best box size for each, and then look at the output differences (I think the Tempest will got lower and louder with less power, but at the cost of a larger box).

    IIRC, the DVCs are better suited for sealed designs (I confess to maybe mixing this up with a different PE driver). JackG is more intimate with the 12" version of the DVC driver.
     
  3. Brian Bunge

    Brian Bunge Producer

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    Jeff,

    I did some simulations on the DVC 12" and I found that I could drop it into the 142.5L alignment on Adire's website and get very similar results. For a sealed enclosure, the DVC will definitely yield a smaller enclosure for a given Q.

    I would assume that you'd get similar results from the DVC 15 but honestly haven't tried any sims. Tell me what enclosure size and tuning you're using (including port diameter and if you're using flares) and I'll run a quick Unibox sim and give you the results.

    Brian
     
  4. Jedd

    Jedd Second Unit

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  5. Patrick Sun

    Patrick Sun Moderator
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    No, the size of the enclosure matters for a sealed box as well as it affects the Q of the whole subwoofer system.

    If the internal volume is too small, the damping is high (reducing low end output), if it's too large, the damping is low (starts to simulate an open baffle (loosey-goosey) situation).
     
  6. jeff lam

    jeff lam Screenwriter

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    well, my design I am currently working on is the 175L tempest Q=.577, 64oz polyfil 4" flared port 13" long tuned to 17.5Hz. This design was from Dan W. I haven't run this design on LspCAD at all. But I think a low Q would be my particular taste. I just liked this design very much because it was much smaller than the 10ft^3 design and yields a tight sound for music but also gives good extension.

    Maybe a sealed design is in my future next. What volume should I use for a low or mid Q for a sealed DVC 15? Maybe .577 or .707.
     
  7. Brian Bunge

    Brian Bunge Producer

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    Jeff,

    DVC 15:

    Sealed-Q=.707, 64.3L (heavy fill), you're below Xmax all the way to 10Hz with 250W

    Sealed-Q=.577, 129.7L (heavy fill), you hit Xmax around 25Hz with 250W

    Ported-175L, 17.5Hz tuning, 4" flared port, 12.75" long with heavy fill.

    Assuming an 80Hz crossover, F3 is around 32 Hz (110dB anechoic) with an F6 of 20Hz (107dB anechoic). Unibox doesn't give Q values for ported enclosures. You'll hit Xmax around 15Hz with 250W and port air speed is below 17m/s until you hit 24Hz and below 26m/s until you hit 20Hz.

    Does this help?

    Brian
     
  8. jeff lam

    jeff lam Screenwriter

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  9. Jedd

    Jedd Second Unit

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  10. Brian Bunge

    Brian Bunge Producer

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    Jeff,
    This is for the ported enclosure. Keep in mind that these are all anechoic responses and you'll have room gain that will bump that up some. Also, consider the fact that you're only 6dB down at 20Hz so it's a very gradual rolloff. We should compare the same alignment for the Tempest to see what the response is like.
    Jedd,
    Yep, that's about right![​IMG]
    Brian
     
  11. Brian Bunge

    Brian Bunge Producer

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    Jeff,

    I'm not sure if it's correct or not, but looking at a quick response in LspCAD, you get a lower F3 (based on an 80Hz crossover) with the Tempest but your response rolls off faster below F3 so that you're actually about 9dB down at 20Hz as opposed to only 6dB down at 20Hz with the DVC 15".

    Again, I haven't used LspCAD that much so someone else may want to varify that.

    Brian
     
  12. jeff lam

    jeff lam Screenwriter

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    Sealed-Q=.707, 64.3L (heavy fill), you're below Xmax all the way to 10Hz with 250W

    Sealed-Q=.577, 129.7L (heavy fill), you hit Xmax around 25Hz with 250W

    How do these two designs look as far as graph, F3, etc.

    Thanks
     
  13. Brian Bunge

    Brian Bunge Producer

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    Jeff,

    64.3L, F3=43.8Hz, about 10dB down at 20Hz (still 100dB though)

    129.7L, F3=43.1Hz, about 7dB down at 20Hz (about 103dB)

    Brian
     
  14. jeff lam

    jeff lam Screenwriter

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    That kind of surprises me. Do all sealed subs behave similar with the F3 in the 40's? What are the specs for the Titan II LE and the Rava both being sealed 12" subs?
     
  15. Patrick Sun

    Patrick Sun Moderator
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    Sealed subs have a gradual roll-off, so you're almost better off not getting too fixated by F3 number, and instead, concentrate on the overall curve and the transient response. Plus room gain will restore a bit of the low end.
     
  16. Brian Bunge

    Brian Bunge Producer

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    Jeff,

    Yes, most sealed subs seem to have an F3 in the 40Hz range. And what Pat mentioned about transient response and room gain are true.

    As far as the Titan II is concerned, it uses some added equalization not only to reduce the system Q, which is around .6, but to also make it flat down to 20Hz. The expensive electronics, along with the furniture quality cabinet are what make it so expensive.

    If you take the drivers from the Titan II (my SV12's) and put them in the same 2ft^3 enclosure with a different amp, your Qtc is actually around .9! It doesn't have very good transient response and doesn't go very deep, but damn if it doesn't have hellacious output in the 40-50Hz range! Shakes my dad's house like a sonuvabitch! I wouldn't use it for music though.

    Brian
     
  17. Peter Jessee

    Peter Jessee Stunt Coordinator

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    Pat Sun said:

     
  18. Robert_Gaither

    Robert_Gaither Screenwriter

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    The Rava is also eq'ed as well (it states it on their site) and if you are concerned about roll-off then corner load to get the maximum gain from a room (just make certain this corner doesn't have a doorway near it).

    The funny part is you look at the roll-off these great drivers and makes you wonder about those other store models...
     

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