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Thinking similiar to Statement/Khanspires but ...

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  • #76
    Take a look at this. This is how I would approach it.

    Edit!.... The delay mentioned on line 10 is added to the tweeter, not to the mid. I'll fix the jpeg shortly.
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    Last edited by rpb; 10-17-2017, 06:34 PM.


    • #77
      Originally posted by Kornbread View Post

      You guys are going to say 'what in the heck is this nut job doing?" Just trying to figure this out in my own head. The mids are offset 5" from the tweeter and the woofers 8". If I did this correctly. Measuring on tweeter axis @40" (~1m) means the distance from mic to mid increases by 8mm, and the distance to the woofer increases by 53mm. This is to the front plane of the speaker = plane of the tweeter.

      When building a passive crossover in PCD, is it the distance to the back of the woofer cone, from the front plane of the speaker, that we measure to get Y offset? Then when working with something like the minidsp, where we can set delay, would we add the Y offset (depth of cone behind front plane of speaker) of the individual drivers to the difference in paths traveled for each driver to get individual driver delay settings in the ballpark?

      The distance from the front of the speaker to the back of the mid cone is 21mm, the woofer 35mm.

      Then the total excess distance from mic to mids would be 8+ 21=29mm, the woofers 53+35=88mm. On the minidsp delay for .028m. is .08ms (.08ms is the closest to .029 the setting will allow), and 88mm for the woofers translates to [email protected] (again not exact but as close as mini would allow).

      I'm really bad at transposing things ... and not that great at engineering kinda' things either, but ... the tweeter needs delayed by .26ms and the mids by .08. Theoretically this should roughly 'time align' the drivers??? What should this do to freq. response?


      But whoa ... look at the differences in rise times of the individual drivers. Can this really be time aligned? How?


      My ramblings, not trying to question anyone's logic, just trying to work things out in my head so I can understand. You guys are the teachers, I'm the student ... in the corner.

      The geometry at 1m is different than at 3m. (Your listening distance, roughly.) In PCD, you can change the distance. Much, or likely all of your thinking / concerns, are accounted for in the software.

      It would be nice to measure at 3m, but that requires a lot of space. For the tweeter crossed at 2.5k, you could measure from 2m, and gate enough to see if everything works as expected.

      For woofer x-over, it helps to get creative, or trust your ears, or both. (See my comment about adding some additional delay at the end of my list.) I'm not sure you need additional delay, but you can try it easy enough.