• RE: Series vs Parallel XO & Maggie Physics. - Davey 12:29:38 07/17/10 (2)
  In Reply to: RE: Series vs Parallel XO & Maggie Physics. posted by DrChaos on July 17, 2010 at 10:59:56

  
  
  

  
  If anyone's interested here's a measurement I did a few years ago. (Copy/paste the link into your browser to see a larger version.)

  http://orion.quicksytes.com/content/mmgxcoup.jpg

  This test was exactly as I described.....the woofer xducer of my MMG driven with pink noise and my spectrum analyzer monitoring the tweeter xducer. (A differential measurement that shows exactly how much voltage is induced in tweeter by driving the woofer.)

  The blue trace on the bottom is a reference with the measurement channel inputs shorted together to show the baseline "noise" of my test setup.

  The red trace at the top is an Adire DPL-12 (dual voice coil) woofer with one coil driven and the other monitored. A theoretically perfect motor/generator would yield a flat trace at 0db over the full frequency range. At higher frequencies you can see it's pretty close to "perfect."

  The yellow trace is the measured response from my MMG tweeter xducer.

  Interesting results eh? :)

  Cheers,

  Dave.

  
  
  

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  Edits: 07/17/10   07/17/10   07/17/10   07/17/10

  • IM distortion - mäç 13:28:23 07/17/10 (1)
    In Reply to: RE: Series vs Parallel XO & Maggie Physics. posted by Davey on July 17, 2010 at 12:29:38

    What you've measured is the IM distortion induced by the driven woofer panel. Can you translate your yellow curve into a precentage?
    

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    • RE: IM distortion - Davey 14:55:01 07/17/10 (0)
      In Reply to: RE: IM distortion posted by mäç on July 17, 2010 at 13:28:23

      You can visually translate it. -20db = 10%, -40db = 1%, -60db = 0.1%, -80db = 0.01%, etc, etc.
      
      I did this about three years ago. I need to repeat the test using ARTA and a different excitation. A shaped tone burst vice the pink noise would better illustrate.
      
      There's a certain amount of mutual (electrical) coupling contained in that measurement as well. The only way to separate that out to yield the actual distortion caused by the mylar movement would be to remove the mylar from the frame or to constrain the mylar movement somehow. Neither easy to do. :)
      
      Anyways, what it shows (in my opinion) is that the "coupling" (electrically and physically) between drivers co-located on a single mylar membrane is not all that great.
      
      Cheers,
      
      Dave.
      

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