Sealed enclosures with plate amp bass boost

Discussion in 'Archived Threads 2001-2004' started by Rory Buszka, Nov 26, 2002.

  1. Rory Buszka

    Rory Buszka Supporting Actor

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    I have a question about the Parts Express subwoofer amplifier. I am planning to build a 1.2 cubic-foot sealed subwoofer and I will be needing a bit of bass boost help from the amplifier. The 300-794 allows up to 5 dB of boost but my question is:

    does anyone know the slope of the EQ in the 300-794? (e.g., 12dB/oct, etc...)

    Also, will a Qts of about 5 destroy a sub driver with a good 25mm of mechanical Xmax? What should I be careful of if I pursue this? At only 270w (the 300-794's measured power into 4 ohms) am I better off with a Q of about .6?
     
  2. Ryan Schnacke

    Ryan Schnacke Supporting Actor

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    "The 300-794 allows up to 5 dB of boost"

    The 300-794 can be modified for just about any amount of boost. Its just that they've only provided values for up to 5dB of boost.

    "does anyone know the slope of the EQ in the 300-794? (e.g., 12dB/oct, etc...)"

    The boost will look like a hump localized around Fboost and just before the rumble filter cuts the frequency response. The rumble filter is 12dB/octave.

    "will a Qts of about 5 destroy a sub driver with a good 25mm of mechanical Xmax?"

    Qts is a property of the driver itself. You meant Qtc, right? Qtc=5 is a LOT to overcome and would require huge amounts of power and driver excursion. But a Qtc=0.6 is just about right even without boost. You could add a little to improve low-frequency extention.

    But remember that for every 3dB you boost you're increasing the power requirements by a factor of 2. So if you've got 6dB of boost you'll reach max power (say 250watts) first at the boost frequency. Everywhere else you'll only be running 62.5 watts. You see how this kind of boost quickly cuts down your effective power limits and 250 watts isn't just a whole lot to start off with.
     

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