Still working on my Tempest Proyect (preliminary graph response)

Discussion in 'Archived Threads 2001-2004' started by Manuel Delaflor, Aug 20, 2002.

  1. Manuel Delaflor

    Manuel Delaflor Supporting Actor

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    Hi all.
    I have been working for about three weeks on my Tempest Sonosub. The sonotube is 18" and 54" tall (I discounted here the MDF's for the driver and the port). My calculations are 225L tuned to 20.50 using a 6" port diameter with a length of 19.7". According to UNIBOX this would give an F3 of 21Hz, which is apparently the case.
    At the time I ordered the Tempest I ordered a calibrated mic also, but the guy who told me about it resulted to be a fraud. So I don't have the correct tool. Anyway, using my SPL Meter I get this graph at my listening position.
    Frequency Response from 10 to 100Hz at listening position
    This the raw data using the SPL Meter as a mic, without calibration. I know it is tunned to 21Hz, but I don't like the fast roll-off after that precise point. Perhaps the SPL Meter has something to do about it, or perhaps my room (which resonate between 40Hz and 50Hz by the way).
    Anyway guys, what do you think about it? Should I tune it lower? I want to get around 16Hz at decent SPL's if possible.
     
  2. Patrick Sun

    Patrick Sun Studio Mogul

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    It looks fine. Have you actually listened to it playing DVD LFE audio tracks, or CD music tracks?
     
  3. Dustin B

    Dustin B Producer

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    If you want decent 16hz output, tune it lower [​IMG] Although don't let the port get any longer than 30".
    Have you tried adding a correction file for the RS meter into the program you're using? The RS meter rolls off pretty heavily in the last octave.
     
  4. Manuel Delaflor

    Manuel Delaflor Supporting Actor

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    Patrick,
    I have tested it with test tones I have made myself, and with lots of MP3's that are around the net to test subwoofers. The baddest bass is on a certain track that have the tyrannosaurus, this track has LOTS of energy below 20Hz.
    Dustin,
    I wonder about your recommendation for the port length? and about how many dB at 20's 30's I will lose by tuning that low? The curves on Unibox shows a dramatic fall.
    By the way, I assume the graph is loading ok. Oh, one thing more. I have discovered that if I open a closet I have in the room I can boost the output several dB's from 25Hz and up, but totally destroy any output below that level. It is like having two different subs! [​IMG]
     
  5. Patrick Sun

    Patrick Sun Studio Mogul

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    Well, you can measure all day, or actually enjoy the fruits of your Manuel labor! [​IMG]
     
  6. Manuel Delaflor

    Manuel Delaflor Supporting Actor

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    Patrick, Lol
    To all:
    I just visited this link again:
    All mighty comercial subs
    And Im Very Very happy to see that my graph (even using an SPL Meter as a mic) compares favorably to all those state of the art subwoofers!
    [​IMG] [​IMG] [​IMG]
     
  7. Brian Bunge

    Brian Bunge Producer

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    Pat,
    GA Tech has produced many an engineer, but I imagine very few comedians! [​IMG]
    BTW, I got an email at work from someone titled "New Manuel" for an application we use. I couldn't help but inform him that Manuel was a small Mexican boy! [​IMG]
     
  8. Hank Frankenberg

    Hank Frankenberg Cinematographer

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    My goodness - five thousand comedians out of work and engineers are trying to be funny. Tsk, tsk, tsk. What's the world coming to?
    Brian, get back out in the shop - you've got lots of MDF dust-making labor ahead of you.[​IMG]
     
  9. Manuel Delaflor

    Manuel Delaflor Supporting Actor

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    Guys guys
    jokes aside...
    what about my graph? [​IMG]
    This weekend I will lower the tuning point and see the changes on the response. If there is enough interest I will upload some distortion graphs also.
     
  10. Patrick Sun

    Patrick Sun Studio Mogul

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    Lowering the tune will drag the response down a bit from 30Hz down to under 20Hz.
     

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