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Different Leslie Crossover Designs

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  • Different Leslie Crossover Designs

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ID:	783510Click image for larger version

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ID:	783509 Hi folks. I’ve seen two different crossover designs and wonder if there are any fundamental differences between them. Example, would there be any advantage to one or the other given the placement of the inductors to each other, etc? Or are they essentially the same?

  • #2
    Purely by intuition , and because of how it looks , the right one must be the most exquisite.

    Comment


    • Dik van der Noot
      Dik van der Noot commented
      Editing a comment
      Is there any factory specification , how long the Leslie needs to warm up , before this right crossover reaches its full bouquet ? Just curious.
      https://youtu.be/ZMP8AuB__as

  • #3
    The style on the right above, built on masonite, was used by Leslie from ~1958 until some point in the mid/late 1970s. They were enclosed in a cardboard cylinder. Close to 1980 or so, Leslie started building them on a piece of wood. This may have been when construction moved to Illinois, but I'm not sure. The film caps shown on the left would not be original to that crossover. I would say that those two are basically the same except that the one on the right still has its original dual section capacitor.

    However, there were actually four styles of Leslie crossovers. The earliest were potted in tar in a wooden box and had a harness attached that plugged into the amp. Both speakers also plugged into the amp. The second style used a wooden box with speaker sockets on the crossover. Both these earlier crossovers used laminated steel inductors, which are superior to the ferrite core inductors in that they do not saturate as easily. Laminated steel inductors are one reason why the 1950s cabinets sound so good, but ferrite core inductors are less expensive.

    I have copied the 1950s crossovers using the original crossover circuit and modern laminated steel inductors. I also orient the inductors so they're not parallel to one another to minimize field interaction.

    I'm David. 'Dave' is someone else's name.

    Comment


    • Rich V
      Rich V commented
      Editing a comment
      David, would the one on the right with the original cap pack have steel inductors? Or thereabouts that timeframe? Was the difference in sound significant between steel and ferrite?
      Last edited by Rich V; 10-12-2021, 05:10 PM.

  • #4
    Neither of the two photos are laminated steel inductors. I’m not certain what precisely makes laminated steel inductors sound better than ferrite core inductors, but the laminated steel inductors are much larger physically.

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    • #5
      Originally posted by muckelroy View Post
      Neither of the two photos are laminated steel inductors. I’m not certain what precisely makes laminated steel inductors sound better than ferrite core inductors, but the laminated steel inductors are much larger physically.
      Inductors are interesting components, arguably the least ideal of the LCR group since they tend to have significant DC resistance and change value with applied current. Laminated steel inductors are basically built like transformers -- just without secondary windings. In fact, the filter choke in every Leslie amp is a laminated steel inductor. All the little filters on the tone generator are laminated steel inductors. Compared to ferrite, laminated steel inductors do not saturate as easily. When an inductor saturates, its inductance value changes, so steel-core inductors remain more stable in value at larger signal levels. This keeps the crossover output stable.

      I did a blind test with some jazz organ players once, and they were able to tell the difference with no difficulty. One of the main observations was that the harmonics in bass notes were a lot more distinct.

      The 21H in Rudy Van Gelder's studio where Jimmy Smith made his famous early recordings had the laminated steel inductor crossover type. All 31H, 21H, 44W, and 46W cabinets have them.

      I'm David. 'Dave' is someone else's name.

      Comment


      • Sweet Pete
        Sweet Pete commented
        Editing a comment
        44W box can also be solid state amped and use the '330' passive crossover design.This ancient first series hand made SWR Pro sounds great powering one.EQ required so the X-over needs to be 'rounded up'.44W x-over stays!Has the B2 hangin' off it,with older preamp chugging along while '53 is on the bench,deja vu,2001.
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