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Inductor DCR effect on FR - tweeter/woofer

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  • Inductor DCR effect on FR - tweeter/woofer

    So i was doing inductor tests and was wondering how to confirm the effect of DCR on both the tweeter and woofer circuits

    I have two 0.60 mH speced air core coils for the tweeter. But one is way larger with lower DCR than the other. Which one should i be using? Or is it dependent on the desired frequency shaping?
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    The original tweeter circuit design doesn't specify the DCR, but the woofer circuit does. And on both of my woofer coils the DCRs seems way off. Is this something to be concerned about?

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    other crossover values removed to respect designer's wish

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  • #2
    The way to model the effect of DCR is as a resistor of the DCR value in series with the inductor. The primary result of high DCR is resistive insertion loss.
    www.billfitzmaurice.com
    www.billfitzmaurice.info/forum

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    • #3
      The DCR will be contingent on whether it is laminate core or air core as well as the gauge of wire. Lower gauge (thicker wire) will reduce DCR and increase cost. Laminate core allows lower DCR for a given gauge and thus a more cost effective solution. However, it can effect the sound quality so air core is typically used in tweeters and for lower levels of mH but large mH inductors in woofer circuits often use laminate core for cost savings.

      This laminate core inductor (as recommended per your diagram) has DCR of 0.36 ohms.

      (Edit: I realize this was not your exact question about how it affects the response and you may already know what I posted)

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      • #4
        Ideally the least amount of resistance, Added resistance is insertion loss, which leads to attenuation. The inductor resistance should also be included into your crossover calculations. If you can model it in the software you are using and get the results you want, then don't worry about it. Some people don't have the budget for the absolute best and end up using what they can afford. Hopefully too, you know that cored inductors of the same value typically have even less resistance.

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        • #5
          The DCR of a "shunt" coil (to ground - as in your tweeter circuit) has much less of an effect on the filter's "transfer function" than the DCR of a series coil ("in-line" w/the driver, as in your woofer circuit). The series coil's DCR (woofer) ALSO has an effect on the box model (that's why there's a place in WinISD that lets you dial in your coil's "series resistance" - same as DCR).

          Ideally, you'd at LEAST use matched pairs of components (did you find your tweeter coils in your parts bin?). With upper-level drivers, in a quality designed system, that varying DCR can help muddle things like the sound stage. If your speakers are for the garage or basement, your 2 tweeter coils won't be as critical, so go ahead and use them (if you HAVE to).

          Did you order a 3mH "iron core" (laminated) coil for the woofer? That's about the only way you could expect to get a DCR near 0.3 ohms. Your woofer coils are matched well enough "to each other". Their higher DCR (approx. 0.3 ohms) most likely will cause about a -1/3dB reduction in the woofer output (it depends on the circuit and the driver, somewhat). I'd go ahead and use them. Odds are your room/room treatments and speaker placement will have a larger effect on the system's sound quality than that extra 0.3ohms of resistance.

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          • #6
            The effect is it lowers the Q. The answer to your question you will find if you put your crossover and drivers into a crossover simulator. Less is not necessarily better as it depends on the filter you are trying to achieve. Usually for the woofer, we try for the lower DCR coils. Larger gauge, sometimes iron core. On the tweeter, I am sometimes adding resistance, so no reason not to buy the cheap 20 gauge coils.
            In other words " IT DEPENDS"

            Please read Chris's last sentence carefully. ( Post #5) Read it again. Make a poster out of it.

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            • #7
              Originally posted by Chris Roemer View Post
              Did you order a 3mH "iron core" (laminated) coil for the woofer? That's about the only way you could expect to get a DCR near 0.3 ohms. Your woofer coils are matched well enough "to each other". Their higher DCR (approx. 0.3 ohms) most likely will cause about a -1/3dB reduction in the woofer output (it depends on the circuit and the driver, somewhat). I'd go ahead and use them. Odds are your room/room treatments and speaker placement will have a larger effect on the system's sound quality than that extra 0.3ohms of resistance.
              3.15 mH, .11 (point one one) Ohms! Really large gauge wire.

              Click image for larger version  Name:	DSCF0629.jpg Views:	0 Size:	840.0 KB ID:	1450326
              Last edited by AEIOU; 09-04-2020, 11:33 PM.

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