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Simple crossover Series resistor question..

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  • Simple crossover Series resistor question..

    Putting a padding resistor "After" the crossover (assuming 2nd order) will attenuate tweeter evenly or not?
    I have read it both ways, I realize before crossover will be fine and will attenuate all tweeter frequencies.

    Just a theoretical question, I realize L-Pad keeps impedance same....

  • #2
    Both before and after will essentially change the dcr of the circuit (think of it as a loop anything in the path affects impedance)
    Although before the filter affects it differently than after, the best way to see how it changes your filter is with measurements.
    I will try to post something later showing the results of both. Do you have measurement gear or crossover simulation?
    just adding the resistance into the dcr of the voice coil will show you roughly what it will change with your filter,
    One thing you can count on is it lowering the frequency of the filter as you raise the impedance.
    Guess xmax's age.

    My guess: 15. His grammar is passable. His trolling is good.

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    • #3
      Kevin, it is easy to view the effects yourself by playing around in PCD, WinPCD, Xsim, etc. Just load up a tweeter, add a 2nd order filter, then start adding resistors in various places. A single resistor will not attenuate evenly over frequency, because the driver is a complex impedance, not purely resistive unless we are looking at an AMT, ribbon, planar. Often the non-linear attenuation is advantageous if the response is non-linear to begin with.

      If you have the LCD cookbook, look under the driver attenuation section, it is well explained there as well.
      "I just use off the shelf textbook filters designed for a resistor of 8 ohms with
      exactly a Fc 3K for both drivers, anybody can do it." -Xmax

      Comment


      • #4
        Resistance post-filter will mess up the transfer function, so don't do that. Figure out what you need for attenuation, then calculate the resistor values required for a post-filter LPad.
        www.billfitzmaurice.com
        www.billfitzmaurice.info/forum

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        • #5
          http://www.erseaudio.com/CrossoverCalculators
          Guess xmax's age.

          My guess: 15. His grammar is passable. His trolling is good.

          Comment


          • #6
            Originally posted by dcibel View Post
            Kevin, it is easy to view the effects yourself by playing around in PCD, WinPCD, Xsim, etc. Just load up a tweeter, add a 2nd order filter, then start adding resistors in various places. A single resistor will not attenuate evenly over frequency, because the driver is a complex impedance, not purely resistive unless we are looking at an AMT, ribbon, planar. Often the non-linear attenuation is advantageous if the response is non-linear to begin with..
            Yes, every crossover topology/tweeter combination is different. It's a simple task to investigate the impact with software.

            dlr
            WinPCD - Windows .NET Passive Crossover Designer

            Dave's Speaker Pages

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            • #7
              Do you really think anyone here that has more than a rudimentary understanding of crossover design would bother with this? Are you trying to insult us?
              https://www.facebook.com/Mosaic-Audi...7373763888294/

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              • #8
                Yes I am trying to insult you. Actually I am trying to help the Kevintomb I'm guessing he has not seen the L-pad
                calculator... Chill bro.
                Guess xmax's age.

                My guess: 15. His grammar is passable. His trolling is good.

                Comment


                • #9
                  Thge lpad calculator is just as useless unless assuming a flat impedance.
                  https://www.facebook.com/Mosaic-Audi...7373763888294/

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                  • #10
                    Use the zobel calculator while you are at it...
                    Guess xmax's age.

                    My guess: 15. His grammar is passable. His trolling is good.

                    Comment


                    • #11
                      Originally posted by xmax View Post
                      Use the zobel calculator while you are at it...
                      And what function would I need that for? Another function that is rolled into the components already in place, if in fact it is actually necessary. And it RARELY is.

                      As per the other thread, we are still waiting to even see ONE speaker you have designed.
                      https://www.facebook.com/Mosaic-Audi...7373763888294/

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                      • #12
                        Hey kevin t., and the answer is . . .

                        in ONE particular example (using a fairly "heavy" 8n resistor), compared to the 8n "out front", the 8n of series resistance "in back" (just before the tweeter) keeps the output at the top end (16k-20kHz) about the same, but actually "lifts" (gives less attenuation to) the output near the Fc by around +2-1/2 dB. The effect is less pronounced w/smaller resistance values.

                        So, compared to "out front", moving the resistance to the rear will tilt the output down (at the top end).

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                        • #13
                          Originally posted by billfitzmaurice View Post
                          Resistance post-filter will mess up the transfer function, so don't do that. Figure out what you need for attenuation, then calculate the resistor values required for a post-filter LPad.
                          I've done that intentionally a couple times, finding that it moves the phase while adjusting attenuation a bit. For example I'll adjust the resistance while watching the reverse null in WinPCD to help improve the phase alignment, flipping polarity often to watch for the best compromise between level and phase alignment.
                          Electronics engineer, woofer enthusiast, and musician.
                          Wogg Music

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                          • #14
                            Such a joker xmax, at least we know how you design your crossovers now!
                            "I just use off the shelf textbook filters designed for a resistor of 8 ohms with
                            exactly a Fc 3K for both drivers, anybody can do it." -Xmax

                            Comment


                            • #15
                              Originally posted by billfitzmaurice View Post
                              Resistance post-filter will mess up the transfer function, so don't do that. Figure out what you need for attenuation, then calculate the resistor values required for a post-filter LPad.
                              Sometimes a "messed up" transfer function is a good thing, to correct a messed up frequency response. I really wouldn't have expected a response like this from you, Bill.
                              "I just use off the shelf textbook filters designed for a resistor of 8 ohms with
                              exactly a Fc 3K for both drivers, anybody can do it." -Xmax

                              Comment

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