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I could really use some help designing 3 way Crossovers

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  • #61
    This keeps over 6ohms. Power distribution between parts and speakers looks good. The XO could probably benefit from some simplification.
    Worst of all though, this doesn't account for driver timing/Z-axis, so the summation at XO points could be (and likely IS) quite different in the real-world....though I tried to compensate a little by aiming for slightly steeper slopes and lower positioning for the high-pass around 2K instead of 2.5-3K which should make the timing differences/mistakes at least a little more suble...I hope.


    Click image for larger version  Name:	3Way DC schematic.png Views:	0 Size:	9.3 KB ID:	1450746 Click image for larger version  Name:	image_87097.png Views:	6 Size:	115.2 KB ID:	1450747 Click image for larger version  Name:	image_87098.png Views:	5 Size:	18.5 KB ID:	1450748

    EDIT: Oh poop, I left one of the large inductors with a value that isn't a whole number, which means it's harder to find affordable Dayton SolidCore versions (or means you'll need to do a little manual unwinding) neither of which is a great option. :( That 5.6mh inductor on the mid could easily be 4mh or 5mh OR skipped altogether since the mid is in a nice little sealed enclosure and the first capacitor is already pretty small on it.
    Those resistor values on the inductors are just how the program shows the natural inductor resistance...they aren't additional parts. It's still 13parts though, which is more than I'd like.
    Last edited by LOUT; 09-10-2020, 12:14 PM.
    My first 2way build

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    • #62
      Okay. Simplified it a little (down to 10 parts), checked part values to make sure they're commonly available, and tried to check it against a fairly wide range of driver timings/Z-axis offsets which seems to look alright though some will want the tweeter polarity reversed (listen for a null around 2Khz).
      Still open to any criticism because I'm sure I've got a lot to learn (and I still have no idea what the real offsets for these drivers are when all of them are surface-mounted).

      Click image for larger version  Name:	3Way DC schematic.png Views:	0 Size:	8.7 KB ID:	1450754 Click image for larger version  Name:	image_87101.png Views:	6 Size:	110.8 KB ID:	1450755 Click image for larger version  Name:	image_87102.png Views:	4 Size:	17.0 KB ID:	1450756

      EDIT: For anyone super new to this, the gradual bass-bump below 500hz is a ~4db BaffleStepCompensation to help make up for some of the natural bass rolloff that'll happen when frequencies get low enough that the speaker's front-baffle is no longer large enough to reflect them. I think this is probably starting a little high for the size of this speaker-baffle (starting the slope around 250hz would be more ideal), but larger inductors get expensive pretty fast and this should still be close....and probably a little more forgiving if there ends up being poor timing alignment betweent the woofer and mid.
      Last edited by LOUT; 09-09-2020, 09:37 PM.
      My first 2way build

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      • #63
        LOUT...... Try these changes.

        On the woofer, add an impedance compensation of 50uf, and 20 ohms.

        Bump the mid high-pass cap up to 50uf. Check out the reverse null! Pretty!

        This still has a lot of BSC, which might be too much if the speakers are on the floor.

        (Continue to reduce BSC).

        The next changes get tricky. Remove the mid padding resistor. and change the 2mH coil to about 1.5mH. Gets harder after this, but you might want to try just for fun.

        2k might be too low for this tweeter.

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        • #64
          Originally posted by rpb View Post
          LOUT...... Try these changes..
          That does line up really nice (albeit still without any driver Z-axis offsets input). Let me know if I missed anything.
          I tweaked the tweeter HighPass a tiny bit to keep it from falling under 6.6ohms. Same for the mid's LowPass, though it does still fall under 6.5ohm around 600hz.
          Click image for larger version  Name:	3Way DC schematic Zobel.png Views:	0 Size:	9.1 KB ID:	1450792 Click image for larger version  Name:	3Way DC graphs Zobel.png Views:	0 Size:	113.5 KB ID:	1450793




          I tried to borrow some of that woofer zobel knee softening by just adding a small resistor to the existing capacitor instead of adding a separate, true compensation line...my woofer tweak isn't quite as effective for aligning the timing and lowering the woofer's low-mid-freq (again, without any Z-axis/offset information), but it does keep impedance at/above 6.6ohms (for whatever that's worth when the amp should be 4ohm stable).
          Click image for larger version  Name:	3Way DC schematic.png Views:	0 Size:	8.9 KB ID:	1450794 Click image for larger version  Name:	3Way DC graphs.png Views:	0 Size:	113.2 KB ID:	1450795 Click image for larger version  Name:	3Way DC Power.png Views:	0 Size:	20.9 KB ID:	1450796
          Can anyone with a current-gen DC28F comment on how low it can cleanly reach with a 3rd orderXO (or is this 4th order acoustic?) with 40-50watts peaks? I feel like it can go lower from playing around with one, but my ears are FAR from golden and I don't really trust myself to recognize a tweeter in distress.
          Last edited by LOUT; 09-10-2020, 02:27 AM.
          My first 2way build

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          • #65
            A little OT, but I think those cool midwoofer seal/boxes aren't always sold as plant pots. Pretty sure they're also bed risers.
            Just in case someone wants to use them and can't find them in a gardening section....they might also be hiding in with bedding/decorating .
            My first 2way build

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            • #66
              Originally posted by rpb View Post

              You don't see the measurements? That's all I attached.
              OK yes, I see the measurements. Thanks. I thought you may have also shared a design.

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              • #67
                Originally posted by LOUT View Post
                A little OT, but I think those cool midwoofer seal/boxes aren't always sold as plant pots. Pretty sure they're also bed risers.
                Just in case someone wants to use them and can't find them in a gardening section....they might also be hiding in with bedding/decorating .
                You might be right, they are pretty heavy duty, there is no hole in the bottom of them and they sell them in packs of 4...

                And thanks for contributing.

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                • #68
                  Hi All,

                  My apologies for not updating this thread sooner, but I've been making some tweaks and am finally happy with what I have. My final crossover is below. I also wound up packing the ports, the bass was too boomy with them open. The bass sounds tighter with the ports sealed and there is still plenty of low end impact. (Love those big woofers) It's been a fun project and I've learned a lot, including the fact that I don't know much about speaker design.

                  Thanks for everyone's help. The next project I tackle I'll ask about driver selection first.


                  Attached Files
                  Last edited by clang; 11-21-2020, 09:41 AM.

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                  • #69
                    It looks like the tweeter might benefit from a 1ohm resistor between the capacitor and amp, both to tame the 5-8khz response down a little bit and push the impedance back up around 3.5ohm....otherwise I think impedance around 5-8khz drops below 3ohm, around 2.5ohm. Most of the time it'll probably just run the amp a little hot, but I think there's a small chance it might break something eventually, particularly if you crank it up.

                    Glad to hear you got it tweaked so you're happy with the sound. Nice work!
                    My first 2way build

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