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Wondering if a Classic 2.5 clone can be made with a series crossover on the woofers

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  • Kootskid
    replied
    Thanks Wolf, also found out that Exodus anarchy woofers were 8 ohm rather than 4 ohm. I think I have used everyone's time enough on this subject, so I will try the Lout/Roemer x-over. If that does not work, then maybe a MTM in series. Next time I will buy the components needed for the build, rather than trying to re-invent the wheel.

    Thanks to all that have contributed.

    Myles

    Leave a comment:


  • Wolf
    replied
    That's a basic SXO, 3rd order electrical on both driver with a notch for impedance and a notch for breakup, and the x.5 coil (parallel style) to the second woofer. This really is not the best solution with 4 ohm woofers.

    Later,
    Wolf

    Leave a comment:


  • Kootskid
    replied
    Also, while cruising some audio websites I came across a series crossover used by CJD in his Asonica 2.5TMM build. A few more parts and complexity, but maybe some insight also. Here is the link:

    Leave a comment:


  • Kootskid
    replied
    Wolf,

    Thanks for the comments. Since this is a dark horse, I would like to build the LP circuit in an enclosure. While I am doing that, I will finish my speaker building course and hopefully acquire measuring tools to see what is happening. Then I can report back with something useful (hopefully).

    Myles

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  • Wolf
    replied
    You'll need the upstream voltage divider for it to even remotely work, so the xover is important.

    It may have had something to do with the path of least resistance as to why this does not work. The bass frequencies will be lower impedance through the woofers than the cap and pass through both. I can't guarantee the upper mid frequencies will bypass the capped-off woofer.

    Later,
    Wolf

    Leave a comment:


  • Kootskid
    replied
    Yeah, I see your point. Will slap some cheap cabs together, hopefully in the near future to give a test. Should I also wire up the tank circuit and the zobel, or is the large cap good enough for the test.

    Myles

    Leave a comment:


  • Chris Roemer
    replied
    Sure, but woofers don't sound like much in "free air". If you had measuring equip., you could maybe tell something by close mic'ing them. Will you able able to judge "by ear"? I'm not sure.

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  • Kootskid
    replied
    Chris,

    Thanks for the info. Just to test the concept, could I wire the woofers in series w/large cap on the bench, rather than building a cabinet at the present.

    Myles

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  • Chris Roemer
    replied
    1. No. the 0.68n(ohm) is NOT a resistor, it's the DCR (resistive component) of the coil (inductor) winding.
    The 16n IS a resistor that's inline w/the tiny notch cap (to prevent a "short" of high or very high frequencies from reaching the amp).
    There are only 3 physical components there: series coil, a tiny cap, and a resistor inline w/the cap.

    2. The 75uF cap passes highs around the woofer (meaning it won't play as high up as the woofer w/OUT the parallel cap).

    3. Funny thing is that both woofers are wired in series. It won't matter which one you put the cap "across" (in the schematic). The only thing that matters is that the cap is in parallel w/whichever woofer gets mounted lower (farther from the tweeter) in the box.

    3.(again) - I mentioned in a post UP^THERE how you could just run the woofer pair (w/one bypassed by a large cap) just to check the feasibility of this topology (since at least someone here, at sometime in the past, claimed that this won't work "properly" - for some reason).

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  • Kootskid
    replied
    Nice Work Lout, Chris, I have a few of questions:

    1. For the tank circuit, can I assume the .68ohm & 16ohm resistors are in parallel and replace it with one resistor wired in series with the coupled 1mH inductor and 0.47uF cap. ?

    2. What is the purpose/influence of the 75uF cap and is influence seen by both woofers or just the first one.?

    3. On the schematic, D11 is the upper woofer and D12 the lower woofer. ?

    3. Is there anymore items that need to be discussed before I give this a try. ?

    Regards,

    Myles

    Leave a comment:


  • LOUT
    replied
    Originally posted by Chris Roemer View Post
    Lout, If you drop the "notch" cap from 1.5uF down to 0.47 (which pushes the 3k breakup down another -10 to -11dB) I think we've got a winner.
    Nearly the same FR (even a bit flatter) with a Z-min of 7.4n, and THAT's on the tweeter section.
    The need for that notch to be smaller comes from your use of a larger series coil (1.0mH vs my 0.50).

    My vers. of Lout's LP topology (in MY sim) did indeed drop to 3.3n in the 300-400Hz range. (I didn't see that the OP requested/required an 8n load.)
    Interesting. With the FRD and ZMA files I'm using (from PE, not measured) it looks like shrinking the LP notch cap from 1.5uF to 0.5uF slightly boosts the top woofer's response at 3000hz (though only by ~3db) while the decreases happen closer to 5000hz and above....Is this probably a quirk from slightly different FRD/ZMA files (yours might be newer or actual measured) or am I maybe misunderstanding something?
    Not that it probably matters a large amount, since it sounds like the cap shrink is either significantly better (from what you're seeing) or mostly the same (from what I'm seeing in Vcad)....so I'm not arguing, just trying to understand why it looks different on my end.

    If it helps anything, here's what I'm seeing:
    Click image for larger version  Name:	DC160-4_DC28F-8_2.5way_series_XO-schema.png Views:	0 Size:	6.2 KB ID:	1452375 Click image for larger version  Name:	DC160-4_DC28F-8_2.5way_series_Six-pack.png Views:	0 Size:	112.1 KB ID:	1452376

    OR

    Click image for larger version  Name:	DC160-4_DC28F-8_2.5way_series_XO-schema.png Views:	0 Size:	6.3 KB ID:	1452377 Click image for larger version  Name:	DC160-4_DC28F-8_2.5way_series_Six-pack.png Views:	0 Size:	111.0 KB ID:	1452378


    This is without any Zaxis/timing offset information added, nor any box impulse or diffraction/BSC information....just FRD and ZMA.


    And, as Wolf warned earlier, there may well be something that goes wrong in a series 2.5way. The sim can't show everything, and there might be something sneaky that makes it sound wonky.
    I'm hoping that it might instead just be a "telephone-game" effect of someone getting bad results a long time ago and the results/info getting a little scrambled along the way and time. I think the current flowing through the cap and adjacent woofer should act similarly to most series XO's...just with another woofer where the tweeter would normally be in a series 2way. I do remember hearing something about woofer sharing a box having different interplay when wired series VS parallel with something interacting physically with one of the woofers..so I'm guessing something electrically interacting might cause a similar effect in some situations. Though I can't remember what this effect was nor if it was even a vetted thing or just guitar player heresay.

    Last edited by LOUT; 09-25-2020, 04:58 AM.

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  • Geoff Millar
    commented on 's reply
    Oops! Missed that mistake, thank you

    As I know next to b- - - r all about crossovers and electronics (ordered a copy of Speaker Building 201 off the Internet but never received it!) I don't understand why a 8 ohm tweeter, with two 4 ohm woofers connected in series to make an 8 ohm load, make for a 4 ohm load when incorporated with the crossover....

    Geoff

  • Chris Roemer
    replied
    Lout, If you drop the "notch" cap from 1.5uF down to 0.47 (which pushes the 3k breakup down another -10 to -11dB) I think we've got a winner.
    Nearly the same FR (even a bit flatter) with a Z-min of 7.4n, and THAT's on the tweeter section.
    The need for that notch to be smaller comes from your use of a larger series coil (1.0mH vs my 0.50).

    My vers. of Lout's LP topology (in MY sim) did indeed drop to 3.3n in the 300-400Hz range. (I didn't see that the OP requested/required an 8n load.)

    Leave a comment:


  • Kootskid
    replied
    Hi Lout, Geoff, Chris,

    I will have an amp that can handle 4 ohms. Also Lout you are correct about having between 4 ohms and 8 ohm system. 8 ohm would be great, but would be satisfied with any above 4 ohms. Following with interest even though i am just learning about x-overs. Lets hope Chris chimes in.

    Myles

    Leave a comment:


  • LOUT
    commented on 's reply
    It looks like the 25uF cap on your LP isn't connected to ground, but otherwise I was also seeing a ~4ohm load from that XO in VituixCAD, so I think that's by design. I'm guessing Chris was aiming for 4ohm because 2.5way builds are more commonly 4ohm (parallel 8/8ohm) and OP is likely aiming to avoid 2ohm moreso than actually needing 8ohm.
    Though I do think (hope?) an 8ohm version might be possible without giving up too much for it...I think the sensitivity and general sound can be kept about the same, though I'd like to hear back from Chris for his thoughts on the ~8ohm XO to make sure I didn't do anything stupid with it.
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