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2.5 way crossover mod to 2 way crossover.

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  • 2.5 way crossover mod to 2 way crossover.

    hi, i am looking to build a 2.5 way speaker, which is a floorstander, but my speaker location might change and a bookshelf would be much better. i already have all the drivers and crossover parts... is it posible to just "cut" the 0.5 portion of the crossover? and use it as a 2 way? 1 tweeter and 1 woofer. i am not interested in the lower extension, as i have a couple subwoofers. thanks in advance Sent from my ONEPLUS A3000 using Tapatalk

  • #2
    You could, but it wouldn't have much/any BSC. What drivers? There might be an existing 2 way XO

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    • #3
      Like Chris said, no BSC after that. The baffle step is probably above where the subs kick in, so you might have a dip there.
      Francis

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      • #4
        Here is the crossover:



        So, If I cut the 0.5 portion in the XO I will have a dip on the woofer's extention? I just need to apply some BSC?

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        • #5
          An interesting question, and one which had occurred to me too.

          My initial understanding about 2.5 way systems was that the second woofer is 'rolled off' earlier than the first to provide BSC.

          This will confuse things, but there may be issues apart from BSC to consider. I'm not a speaker designer and have only successfully built other peoples' designs, but here's an example of an excellent TM design which many have built, including me, which has been modified by its designer to a 2.5 way, also excellent and on my 'to build' list.

          I do hope Mr Carmody doesn't mind my using his work to illustrate a possible issue.

          https://sites.google.com/site/undefinition/classix-ii

          https://sites.google.com/site/undefi...diy/classix2-5

          The interesting thing is that the crossover networks share few parts, Paul's write up notes that as well as dealing with BSC, his crossover also serves to shape the DC160 woofers' midrange response.

          I've no idea whether the Faitals have any similar issue(s), but maybe your crossover might need a little 'tweaking' in addition to addressing BSC?

          Geoff

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          • #6
            Originally posted by mga2009 View Post
            Here is the crossover:


            So, If I cut the 0.5 portion in the XO I will have a dip on the woofer's extention? I just need to apply some BSC?
            You'd have to adjust the tweeter padding too. If that .33 ohm resistor is real, and not just the inductors resistance, i'd remove that. It's better to simulate and measure it, but you could unwind the 4.3mh inductor down to 2.5-3.5mh and swap it for the 1.3, and put a resistor across the tweeters terminals (4-10 ohms maybe?)

            How big is the bookshelf? Big enough to fit a shorter TMM cabinet with the same drivers?

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            • #7
              Originally posted by Geoff Millar View Post
              My initial understanding about 2.5 way systems was that the second woofer is 'rolled off' earlier than the first to provide BSC.
              +1. Rather than pad down response above the baffle step frequency by 6dB you use a second woofer only below the BSF to increase voltage sensitivity by 6dB in that pass band. It doesn't matter if the speaker is a floor stander or bookshelf. A larger concern would be whether a pair of these drivers would function well in a bookshelf. That would seldom be the case if they were suitable for a much larger floorstander.

              www.billfitzmaurice.com
              www.billfitzmaurice.info/forum

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              • #8
                Usually ribbons (which typically have a nearly "flat" imp. profile) can use pretty simple XOs. This one's looks atypically "complex".
                The 2nd woofer mostly just boosts the response below about 300Hz by 4-5 dB.

                I've worked out a MUCH simpler HP (for the tweeter) and an alternate LP (including BSC), but I doubt they make use of the XO parts you've already got.
                Interested?

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                • #9
                  Originally posted by Chris Roemer View Post
                  Usually ribbons (which typically have a nearly "flat" imp. profile) can use pretty simple XOs. This one's looks atypically "complex".
                  The 2nd woofer mostly just boosts the response below about 300Hz by 4-5 dB.

                  I've worked out a MUCH simpler HP (for the tweeter) and an alternate LP (including BSC), but I doubt they make use of the XO parts you've already got.
                  Interested?
                  Chris,

                  I am interested in your XO. Here is a REW measurement at 1 feet on axis 1/12 smoothed, with the Ribbon Tweeter.

                  My XO is a 6.4uf cap and a 8ohm L-Pad resistor from PE at the max setting, and reverse polarity.

                  The thing is that I can get rid of the dip at around 1500hz, but that's not tweeter problem, but woofer, correct?

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                  • #10
                    2nd order filters - w/a "tank" on the woofer. About the same BSC as the orig. (+4dB or so). This is just a TM (for a single woofer). Fc near 1.7k.

                    High Pass (ribbon), left to right (amp to driver): 6n(ohm) series resistor, 6.8uF series cap, 1.0mH shunt coil (to gnd. - can be a #20 coil), 6n shunt resistor (across ribbon).
                    LP: a 3.0mH series coil (iron core for low DCR), and a 6uF shunt cap. There's also a tiny 0.33uF cap across (in parallel w/) the coil to act as a notch near 7kHz.

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                    • #11
                      Originally posted by Chris Roemer View Post
                      2nd order filters - w/a "tank" on the woofer. About the same BSC as the orig. (+4dB or so). This is just a TM (for a single woofer). Fc near 1.7k.

                      High Pass (ribbon), left to right (amp to driver): 6n(ohm) series resistor, 6.8uF series cap, 1.0mH shunt coil (to gnd. - can be a #20 coil), 6n shunt resistor (across ribbon).
                      LP: a 3.0mH series coil (iron core for low DCR), and a 6uF shunt cap. There's also a tiny 0.33uF cap across (in parallel w/) the coil to act as a notch near 7kHz.
                      Chris,

                      Something like this?

                      UPDATE: an inverse polarity in the tweeter gives a better response, so probably made that mistake in the first image.
                      Attached Files
                      Last edited by mga2009; 12-18-2019, 11:30 AM.

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                      • #12
                        The schem. is OK, but you NEED a 0.33uF cap across the 3mH coil - upping it to a 0.68 is probably HALVing the target freq. of the notch filter (which might have something to due w/the big hole near 1-1/2kHz.

                        I THINK you could use TWO - 0.68uFs in series to essentially get 0.34uF - close enough!

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                        • #13
                          Originally posted by Chris Roemer View Post
                          The schem. is OK, but you NEED a 0.33uF cap across the 3mH coil - upping it to a 0.68 is probably HALVing the target freq. of the notch filter (which might have something to due w/the big hole near 1-1/2kHz.

                          I THINK you could use TWO - 0.68uFs in series to essentially get 0.34uF - close enough!
                          Chris,

                          Thanks for your help! I will try the XO right away.

                          Is there any chance I can remove the 6ohm series resistor in the tweeter? I do not suffer of "highs fatigue", on the contrary, I do like my higher frequencies a little hot.

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                          • #14
                            Originally posted by mga2009 View Post
                            Here is the crossover:



                            So, If I cut the 0.5 portion in the XO I will have a dip on the woofer's extention? I just need to apply some BSC?
                            we would not want 2.7 ohms to be series with a woofer. A cascaded 2.5 way would have been a much better design to avoid any phase issues between woofers and maintain the same roll-off for both.
                            Click here for Jeff Bagby's Loudspeaker Design Software

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                            • #15
                              Yup. More often than not, you can say that "generally" each ohm of series resistance cuts output by about 1 dB. If it's too hot w/it out, then try 3ohms.

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