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Thread: Basic questions about schematics

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    Senior Member evans224's Avatar
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    Basic questions about schematics

    I'm looking at the x-over schematics for the L56 and L56A. I can physically see the difference, as I have both. I'm unsure how to wire the drivers so that they are in phase. On the N65, which wire goes to the positive terminals? Black is usually negative, but the black input wire becomes green to the LF, and the red becomes black.

    Looking at the N65A, the same questions apply, but the added twist is that the black input wire and the wht/black wire are shown as input, and the red wire is output? Is there a schematics for dummies guide out there?
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    RIP 2011 Zilch's Avatar
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    That's the phase inversion. The low and mid are out of phase with the HF in N65.

    In N65A, it's the mid that's out of phase with the other two.

    N65B, the mid's out of phase electrically as well.

    Assuming all of the drivers follow the same phase convention, of course.

    [I'll look a FOURTH time to be sure, now....]

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    Senior Seņor boputnam's Avatar
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    Hey, evans...

    For the most part, ignore the speaker binding posts, and only pay attention to the colors of the leads in the crossover. JBL wanted it that way...
    • GRN --> Red terminal on LF transducer
    • WHT --> Red terminal on MF transducer
    • RED or YEL --> Red terminal on HF transducer
    Any lead with BLK goes to the Black terminal on the transducers.

    Keep it simple.

    JBL went through some iterations with the L65 - that's what you are seeing. Overall rule, keep like components like-phased. If that confuses, post again - otherwise follow the above scheme.
    bo

    "Indeed, not!!"

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    Senior Member evans224's Avatar
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    ok, clear as mud.

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    Senior Seņor boputnam's Avatar
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    Quote Originally Posted by evans224
    ok, clear as mud.
    Truly...? If not clear, man, come back and we'll try and walk you through the JBL polarity "legacy".

    As well, you can SEAERCH for "polarity convention" and other, and you'll find yards of observations on this. The "muddiness" is only new to you - we've been through it a bunch of times.

    We are here to help...
    bo

    "Indeed, not!!"

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    Senior Seņor boputnam's Avatar
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    Quote Originally Posted by evans224
    I'm looking at the x-over schematics for the L56 and L56A. I can physically see the difference, as I have both. I'm unsure how to wire the drivers so that they are in phase.
    Hey, evans...

    Re-reading this, I wonder - do you have two pair of L65's? Or, are you using a differrent network in each cabinet? Either way, what you need to do is the same:

    L65
    LF: The 126A is negative, and here wired reverse (through the network) = (+)
    MF: same as LF, negative wired reserve = (+)
    HF: negative wired normal (Red to RED) = (-)

    L65A
    LF: 122A is negative, here wired normal (Red to GRN) so is running (-)
    MF: negative, wired reverse = (+)
    HF: negative, wired normal = (-)

    So, if using both these networks together, your LF's are out-of-phase if connected GRN to Red LF terminal. Pick one and reverse the wires AT the LF. You should notice an increased LF response. Note, this will put the cabinets in-phase with each other.

    However...

    Quote Originally Posted by evans224
    I'm unsure how to wire the drivers so that they are in phase.
    Do you WANT each element like-phased? That was not JBL's design, and doing this will yield a very different response.

    What is it you are trying to do...?
    bo

    "Indeed, not!!"

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    Senior Member evans224's Avatar
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    I have one pair of original Jubals, and I'm attempting to get wiring correct. I bought the cabinets, x-overs and drivers separately. I was confused when looking at the diagrams (what's new). I found the correct x-over for my drivers, the N65's, and installed them. I was not all that impressed with what I heard. I came across a second set of x-overs, which are N65A's and was going to put them in. I know they were made for a different woofer, but everything else is the same. Also, I saw some specs on the L65's, and the 077 is shown to have a 16 ohm impendence, everything else is 8. I am using 2405's with 8 ohms. Is this going to make a huge difference?

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    Senior Seņor boputnam's Avatar
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    No. Should be fine.

    When installing the N65A's, just honor the colored wiring instructions in my first post, here.

    As well, for those that are panting patiently, here is the complete L65 series techsheets (again...).
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    bo

    "Indeed, not!!"

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    Senior Member evans224's Avatar
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    Thanks, I'll give it a shot. Problem is, I always want to know the "why" of things. I guess the JBL folks figured that making some drivers out of phase with others would be a good thing. Some car audio guys do that with front and rear speakers to try to get proper "staging", which is impossible in a car.

  10. #10
    Senior Seņor boputnam's Avatar
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    Hey, evans...

    Oddly, JBL uniquely chose a polarity convention that ended-up being 180° opposite all other manufacturers. Why? No clue. Matters not, except that the world of pro-audio need remember this. And the nasty little secret that it is not universal even within JBL-land - there are a few (thankfully VERY few)variants that are of non-JBL conventional polarity...

    As to the different phasing of transducers within a cabinet, that has to do with imaging, resolution, etc., wrt network topology (I think I have this right - Giskard where am I...? :scared: ) Much of this is personal taste and the "sound of the times". The L100, for example, had a topology and phasing very compelling for it's time - maybe less so, now.

    The only thing to beware of, is having like transducers out-of-phase: keep all your LF's, MF's and HF's like-phased and you'll be rewarded. Particularly an important memory when mixing / pairing JBL's either with themselves, or with other brands (now who the heck would do that!! )
    bo

    "Indeed, not!!"

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    Senior Member DavidF's Avatar
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    Quote Originally Posted by boputnam
    The only thing to beware of, is having like transducers out-of-phase: keep all your LF's, MF's and HF's like-phased and you'll be rewarded. Particularly an important memory when mixing / pairing JBL's either with themselves, or with other brands (now who the heck would do that!! )

    I read and agree with what Bo is saying but I hope he will allow a small edit to prevent some confusion for some readers (maybe)...

    The only thing to beware of, is having like transducers out-of-phase OF ITS TWIN IN THE STEREO PAIR: keep all your STEREO PAIR LF's, MF's and HF's like-phased and you'll be rewarded...

    Thanks, DavidF

  12. #12
    Senior Seņor boputnam's Avatar
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    Yea, David - I can see where what I wrote could be mis-interpreted.

    What I was trying to say, was...

    Each set of LF's should be like-phased.
    Each set of MF's should be like-phased.
    Each set of HF's should be like-phased.

    And, however, the aggregation of components within a cabinet are typically not all phased the same - most commonly the MF is out-of-phase with the LF and HF, but there are of course variantions...
    bo

    "Indeed, not!!"

  13. #13
    Senior Member evans224's Avatar
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    I appreciate the help. I've put in the n65a's and I definitely hear a difference-but not for the better. Sounds a bit muffled on the lower end. I ve got them off the floor now, as people have suggested doing with Jubals. I'll give them a couple of more days, then put the original x-overs back in.

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