Excursion over Xmax

Discussion in 'Archived Threads 2001-2004' started by Jedd, Mar 27, 2002.

  1. Jedd

    Jedd Second Unit

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    As I understand the cone excursion should not exceed the Xmax of a driver.
    According to the LspCAD 100W will drive sealed 3ft^3 parallel shiva near Xmax. Does it mean that I can use my receiver (H/K 520, 75wpc) with it and have all the power I need?
    Shiva specs says I can apply 375W to it - which exceed the Xmax on the 8mm [​IMG]. How bad is that?
     
  2. Brian Bunge

    Brian Bunge Producer

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    Jedd,

    I believe LspCAD shows excursion as peak to peak, so you would divide by 2 to get your true 1 way excursion. So if the Shiva's Xmax is 16mm but LspCAD is stating excursion as 24mm then your true, 1-way excursion is only 12mm, or 4mm below Xmax.

    Brian
     
  3. Jedd

    Jedd Second Unit

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    LspCAD gives me 29.2 mm p-p at 75W

    and it grows up to 39.5 mm p-p at 375W
     
  4. Rudy H

    Rudy H Stunt Coordinator

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    Sounds right. Things in a driver get VERY different once you start running a good amount of power into it. Large Signal Analysis it's called IIRC.

    The suspension limit on the Shiva should be around 40mm or so, so with 375watts I'd recommend extreme caution, but if you go for say the 275watt RMS PE amp, you won't have any trouble.

    What frequency is this excursion spec at though?
     
  5. Jack Gilvey

    Jack Gilvey Producer

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    When you choose parallel voice coils for Shiva, LspCAD will double your input power since it's a 4-ohm load. So, if you put 75 watts in the "Watts into 8ohm" box, you're actually seeing the result of 150 watt input. The way to go is to type in half your amp's rated 4-ohm load...then the program will use the correct power.
     
  6. Jedd

    Jedd Second Unit

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    Hmm.. It's a good point, my H/K520 specs says nothing about 4ohm load, except that it will handle it. So it might be much less then 75W. Well, I could always add a plate amp on the road.

    Cone excurstion - it's slowly falling at 75W (from 29mm)

    Have a moderate max at 125W at 25Hz (33mm)

    In the case of 375W it goes up to 40mm at 35Hz
     

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