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Inductor placement - Overnight Sensation TMM crossover

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  • Inductor placement - Overnight Sensation TMM crossover

    Click image for larger version  Name:	image_90624.jpg Views:	3 Size:	499.2 KB ID:	1469972
    I was hoping somebody could cast an eye over this crossover layout for me. The board will be about 8" x 4", the two larger coils are about 3" apart and they are each about 1.5" from the center coil. Does this look ok? Sorry I couldn't get the image horizontal.

  • #2
    I think that's okay.
    It might work a little better if you rotated the small coil CCW about 45* (so you see the BIG coil when looking through the "hole") AND the Med size coil as well (so its "hole" pointed at the small coil). Of course, the layout wouldn't look as nice then. ;-)


    • #3
      Thanks Chris. I was trying to get the woofer and tweeter circuits on one board which can lay on the bottom of the cabinet.

      Might investigate separate boards mounted on cabinet sides to get better separation of the coils just to be safe.


      • #4
        The distances you stated between the inductors, is that center to center or perimeter to perimeter? The reason I ask is that quite a few years ago (2013) I made measurements of mutual coupling and crosstalk between inductors to determine to my satisfaction how much distance was needed from perimeter to perimeter of air-core inductors laid down flat like the pair on your proposed board. I found that as long as that distance was no less than 2 inches, there would be no problems. So the two coils you show laid down flat will be perfectly fine if the 3" distance you stated is between perimeters. And, since the other coil is turned up and rotated as shown that should be okay, too, with a 1.5" distance (although I did not make measurements for that arrangement in my tests). I assume if you want to dig it up, you might be able to find the thread from 2013 to get the details.
        Edit: I found that thread here:

        Edit 2: I also did a follow-up thread regarding voltage crosstalk between inductors. I did find that thread but my opening post is blank and it was this: Inductor crosstalk.doc

        Edit 3: Here's the link to the crosstalk thread:

        Attached Files


        • #5
          Thanks Paul,

          I had read your threads on crosstalk before posting but the small coil was a spanner in the works as it was less than 2" from the other two coils (diagonally between perimeters). That is why I placed it upright and rotated 90°. Most references I have seen show a coil like this as being postitioned upright, rotated 90° and in line with the center of an adjacent coil. If I move the small coil to the right (down in my pic) to line up with the center of the largest coil they would only be around 0.5" from each other, so I opted to position the small coil between the other two as I figured the greater the distance between the coils the better. I could not find any references for this arrangement however.

          The two larger coils are 3" betweeen perimeters but in my pic only one is laid down flat, I am guessing having one upright won't hurt given the 3" spacing.

          It was a pic you posted of a crossover in the base of one of your speakers which lead me to wanting to position the crosssover on the cabinet floor but with only 8" x 4.5" things got a little tight re inductor placement.

          Thanks again, John.
          Last edited by 01-0077; 05-23-2021, 08:12 AM.


          • Paul K.
            Paul K. commented
            Editing a comment
            Yep, the fact that one of the larger coils is stood up is fine and the 3" spacing is a bonus. Other than a pair of large bookshelf speakers I built for my workshop, I only build floor-standers for personal use, so I usually have lots of room for a single crossover assembly with all of the air-core inductors laid down flat and at least 2" spacing between perimeters.