No announcement yet.

Looking for help - old box, new mid range - rebuild project.

  • Filter
  • Time
  • Show
Clear All
new posts

  • #16
    I simplified the XO a bit. Besides a pr. of tweeters, you'll need:
    2 - 2.0mH coils #257-554
    2 - 0.80mH coils 257-044
    4 - 4ohm 10w resistors #016-4
    2 - 5ohm 10w resistors 016-5
    2 - 1.0uF caps #027-410
    2 - 6.8uF caps 027-424
    2 - 22uF npe caps 027-348

    I'll work up a schematic for you ...
    HP - no changes
    LP - dropped "Zobel" & changed cap values on shunt & notch

    Click image for larger version

Name:	M8N 2way.jpg
Views:	57
Size:	119.6 KB
ID:	1464455

    WOW! (that came in larger than expected)

    HP (tweeter - "negative" polarity): 6.8uF series cap, 0.80mH shunt coil, L-pad: SR / PR = 5ohm / 4ohm (series and parallel)

    LowPass: 2.0mH low DCR series coil (w/bypass "notch"), 22uF npe (cheap) shunt cap - to GrouND
    - notch filter (aka "tank") is a 4ohm resistor and a tiny 1.0uF cap

    Off you go. Have fun ...
    Last edited by Chris Roemer; 02-15-2021, 12:26 PM.


    • dwigle
      dwigle commented
      Editing a comment
      Chris, what application did you use to expand that schematic? thanks

  • #17
    Originally posted by Chris Roemer View Post
    2 - 6.8uF caps 027-424

    Thanks a lot.
    It is EXACTLY what I needed!!

    Just a tiny problem - the cap is OOS.

    I can easily place an order and wait unless you think some other would work as well.
    I will add 4 small boards to assemble the crossovers.
    Thanks again.


    • #18
      try Audyn # 027-116
      (or the Dayton 6.2uF - last resort)

      And boards are OK, but co$t money.
      Look around here.
      Most guys use a piece of hardboard, or even a chunk of old paneling (something 1/8"-1/4" thick - but NOT cardboard / or metal) works great.
      You can keep all the leads "on top", or poke the legs through and solder up on the bottom (back side). That's what I like to do.


      • #19
        Thanks again.
        Just to make sure I read the schematic properly.

        Tweeter side.
        "+" means I pull signal straight from the positive input, then it goes to the tweeter (negative side?) and it grounds there as well? Or it should have been positive?

        supply comes from the plug as well, goes through the circuit and connects to the positive of the speaker.

        Negative side is ground for all pieces (where indicated).

        Regardless - it is AC, not DC, so not really polarity there, but as long as I am consistent it is OK. So assume Red on the amplifier is positive and keep it that way.

        I may return to verify how the cores are connected (input vs output for air and Fe cores).

        Also, regular Sn solder is fine, right or Silver is a must?

        Second part.
        Could you explain me what the circuits will do?
        Correct me if I am wrong.
        I understand the tweeter crossover is to "direct" higher frequencies which cannot be handled by the woofer to tweeter.

        What is the zobel part? I read something about woofer's resistance?

        Finally, one more thing.
        When I was learning about speaker box design, I read something about filling making the apparent volume larger. Does it mean that despite physically being 0.5 ft3, with the fiber will be larger? If so, by how much? I also learnt that it can actually mess up the box if done improperly.
        So what do I do here?

        Off topic.

        Something just popped to my mind I have been wondering about.
        I have 5.1 speakers system where the sub has a switch that supposedly changes the phase of it.

        How do I know if they are in phase or not?
        The 5 speakers are connected same way, that is Red is red for each of them. Sub does not have it. It is a plug.

        Sorry for so many questions.
        I guess I am learning a lot now.


        • #20
          Oh, and in regards of the boards - I was on the verge of free shipping anyway. So their overall cost was basically shipping + 3 USD.


          • #21
            A good book to read is "SpeakerBuilding 201".
            In general, caps pass highs & block lows. Coils block highs and pass lows. Resistors impede voltage.
            GND ("ground") would get wired to your cab's "-" (usually black) term, and connected to the black term. on your amp.
            Your amp's red side ("+") goes through your cab's "+" term (on the left side of each "filter".
            It's common (in this "topology") for the tweeter to get wired "backwards" compared to the woofer.

            NONE of the XO components have a "+" or "-" side, including THESE types of caps (a.k.a. "bipolar"). Only the drivers' "polarity" matters.