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MTM Boombox Crossover Help

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  • MTM Boombox Crossover Help

    Looking to help my brother-in-law with a science project for class. He mentioned building a boombox and explaining how everything works. I have 4 W5-1611SA woofers and a pair of BC25SC06 tweets which I believe would make a great MTM. Both drivers, I believe, look pretty managable but I dont know where to start with the crossover. I know the W5 is a "fullrange" but I have read where it benefits a tweeter, so my thougbt was to cross somewhat high (5-8khz). They will be powered from an amp delivering about 70wpc. Havent settled on an enclosure yet, but Im leaning towards vented just to get into the F3 70-80hz range. Would anyone be willing to help on the crossover design?

  • #2
    Re: MTM Boombox Crossover Help

    cross somewhat high (5-8khz)
    In a MTM config - no
    ( I'd go 2.7KHz )
    "Not a Speaker Designer - Not even on the Internet"
    “Pride is your greatest enemy, humility is your greatest friend.”
    "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

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    • #3
      Re: MTM Boombox Crossover Help

      So with it being an MTM, it should be a lower crossover point?

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      • #4
        Re: MTM Boombox Crossover Help

        Yes. The Midranges being separated necessitate this.
        "Not a Speaker Designer - Not even on the Internet"
        “Pride is your greatest enemy, humility is your greatest friend.”
        "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

        Comment


        • #5
          Re: MTM Boombox Crossover Help

          Ok, and the 2.7khz xover due to the 1.350khz fs of the tweeter?

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          • #6
            Re: MTM Boombox Crossover Help

            Yes - This a case where the old starting point ( 2x the resonance ) is also a frequency commonly used for that Vifa tweeter.
            A higher order filter could allow for a lower Fc ( an advantage of active filters ).
            Or a tweeter with a lower fs could be taken lower.
            "Not a Speaker Designer - Not even on the Internet"
            “Pride is your greatest enemy, humility is your greatest friend.”
            "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

            Comment


            • #7
              Re: MTM Boombox Crossover Help

              Could this woofer tweeter combo work? Is it too much trouble to deal with? Since this wouldnt be a critical listening setup, i dont need superb quality. Im just looking for a xover better than the online calculators

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              • #8
                Re: MTM Boombox Crossover Help

                I think so, ( have not Simulated it )
                CTC distance ( for an MTM ) is only 8.9"
                Traditionally a 3rd order is used with an MTM.
                ( I use a 4th order active ).
                Last edited by Sydney; 02-22-2016, 06:28 PM.
                "Not a Speaker Designer - Not even on the Internet"
                “Pride is your greatest enemy, humility is your greatest friend.”
                "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

                Comment


                • #9
                  Re: MTM Boombox Crossover Help

                  Ok so maybe 3rd on the tweet and 1st on the woofer possibly? Do you mind simulating it?

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                  • #10
                    Re: MTM Boombox Crossover Help

                    I'm on a device w/o sim software

                    *According to the sims ( BassBox "optimum" ) on
                    http://www.parts-express.com/resourc...election-guide
                    A sealed single W5-1611SA: 0.17cu ft (.34 for MTM ) w 109Hz F3
                    A vented single W5-1611SA: 0.44cu ft (.88 for MTM ) w 56Hz F3
                    Last edited by Sydney; 02-22-2016, 06:58 PM.
                    "Not a Speaker Designer - Not even on the Internet"
                    “Pride is your greatest enemy, humility is your greatest friend.”
                    "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

                    Comment


                    • #11
                      Re: MTM Boombox Crossover Help

                      ROT: cross no higher than SOS (speed of sound = about 13,500ips) divided by C-C distance between tweeter and mid.
                      For you: = 13,500 / 4.5" = 3000Hz. Try this:

                      2nd order HP: 6.8uF series cap, 0.40mH shunt coil (#20), L-pad: SR=3n (ohms), PR=2n. (normal polarity)
                      2nd order LP w/Zobel: 1.0mH series coil, 5uF shunt cap (to gnd), Zobel = 15n + 8uF.

                      Vented, in 0.38cf w/a 2"id x 5" long vent. Should do 60Hz. Of course, both sides together make for 3/4cu.ft. IF you ran an MTM (vented), you'd be up to 1.5cf which ain't no boom box. My XO is just for the TM version.

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                      • #12
                        Re: MTM Boombox Crossover Help

                        Wow, thanks for the help everyone! So in this case would TM be perfered for simplicity sake and size savings? I just had 4 of the mids and thought i could put them to use. But my current boombox this will replace is a TM using the same tweeter and NS6 mid and it is sufficient to say the least.

                        Just to double check the crossover I scetched it out in the attachment. Would 5w resistors and 20ga inductors be sufficient? Also, the tweeter is 4ohm and the woofer is 8ohm. I just was gonna check to see if it was accounted for.


                        Click image for larger version

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                        • #13
                          Re: MTM Boombox Crossover Help

                          yup

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                          • #14
                            So Im drawing up the box. Each driver enclosure will get closer to .4cuft. How will that effect tuning?

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                            • #15
                              Close enough.

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