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Thread: A toddler and his JBL 4343B battling polarity

  1. #1
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    A toddler and his JBL 4343B battling polarity

    Imagine for a second that you're teaching a toddler to work out this puzzle box



    Now replace the toddler with me, the box with JBL 4343B and the pieces with wires and polarity but keep the same mindset, we good?

    Ok, so on to the issue here. I own a pair of 4343B with charge coupled network and passive xover between (mid, hf and uhf). The lf driver (2235h) and the rest requires active xover. The rear of the speakers has two sets of terminals, one pair for the lf and one pair for the mid, hf and uhf drivers.

    1) I'm going over the polarity of the system and I hooked up a 9V battery to check the polarity of the woofer. Connecting the speaker terminals to a 9V battery, Red to + and Black to - made the cone go inwards. Since the speakers will be used together with subs where Red to + and Black to - made the cone move outwards I need to make some adjustments.

    2) I did not do a polarity check on the (mid, hf and uhf) wired to the network as I was afraid I might damage something, and I wouldn't know how to see the polarity of the hf and uhf drivers anyways.

    3) Since the speakers require an active crossover they also require four channels.

    4) I assumed it would be as easy as (Amplifier Red to Speaker Black) and (Amplifier Black to Speaker Red) but then I came across this post in the forums http://www.audioheritage.org/vbullet...wfull=1#post30

    Quote Originally Posted by boputnam View Post
    If you are going to reverse the polarity of a JBL cabinet, it must be done AT EACH COMPONENT in the cabinet. You should not simply hook-up the cabinet red-to-black. That will not have the proper effect, because that will result in the signal being pathed through the transducer before the capacitor(s) - this is a DC circuit, and that is backwards. For the crossover network to work properly, the capacitor(s) must see the signal BEFORE the transducer, regardless of cabinet (and transducer) polarity.

    To "correct" or re-phase a vintage JBL cabinet, you need to reverse-wire at each component. Simply alter the signal path AFTER the crossover and before the transducer, at each component binding posts.

    As example, if your cabinet is out-of-phase (negative), and woofer is wired GRN-to-red post, switch the woofer to GRN/BLK-to-red post. Reverse the wiring for EACH component (this will ensure the mid-range stays 180-degrees out-of-phase in 3-way cabinets). The woofer - and cabinet - will then be positive, and industry standard.

    It is handy - but not necessary - to review the network schematics, if you're so inclined, and yours is available:

    Link: http://www.jblproservice.com/pdf/Network%20Schematics/
    A) So now I'm not sure what to do? I can't do as I assumed in point #4?

    B) Should I and how would I go about making the speakers adhere to the current industry standard, please?

    PS: I did read the polarity convention of JBL transducers and systems pdf, but again, refer to the puzzle box, please.

  2. #2
    Senior Member macaroonie's Avatar
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    Be aware that some amplifiers invert the signal. Hence if you are using different amps where one inverts then you have to allow for this also

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    My life just got harder. I'm using a vintage Denon POA 1500 for mid, hf & uhf and a QSC GX5 for the 2235's.

    How can I check if those amps does that, and if they do, then what can I do to diddelido? ....

    Sorry, I mean, if they invert, does that mean that the poles are switched at the amplifier's binding posts? If yes, then I can check the voltage with a multimeter.

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    Senior Member grumpy's Avatar
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    If you have the biamped 4343 working right as a system, just make sure the sub
    is phased appropriately (e.g. if you intentionally overlap the 4343 and sub
    and they're out of phase, you'll get a hole in response that should be easy
    to spot).

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    Grumpy, yes, that's what I've been doing up until now. I'm using DIY subs and midbass modules and these are managed by miniDSP 4x10. I can invert using that (which is what I have done in the past), but I'd like everything to adhere to present standards. Now everything except the speakers are physically wired so that + from battery to red/(+) on subwoofers & midbass modules (SpeakOn) connectors make the cones move outwards, ie positive polarity.

    For the speakers the cone moves inwards when doing the 9V battery test, ie negative polarity.

    The goal is that the speakers are also wired for positive polarity to have a uniform standard across the system.

    I'm not sure what to do to make that happen.

  6. #6
    Senior Member grumpy's Avatar
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    I'm afraid I don't understand the point of your goal.

    The drivers are operating with -intended- phase/polarity with each other, or they are not.
    This is important to get right. It sounds like you have done this.

    If the slope of the electrical crossover has been changed from the original design,
    the necessary phase/polarity of a particular driver -may- also require a change as
    well as some EQ.

    The system is operating with a positive signal providing positive displacement (out) of the
    bass drivers (not necessarily true for other drivers) with red amp terminals connected
    to red speaker terminals, or it is not.

    I won't argue whether this is important or not.

    If it is important to you, make it so. If the bass driver in the 4343 needs to be flipped
    in polarity to accomplish this, then it is important to flip the rest (vs. the factory wired polarity).

  7. #7
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    The only real way to do it right is to use a real time analyzer and see what combination of polarities give you the smoothest room response in the seating area.

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    Ok, thank you guys. I've been using REW to measure and make sure that there is no cancellations in the system that shouldn't be there earlier, but I wanted to make the speakers adhere to today's standard wiring convention so everything had the same starting point just to make things easier on my peanut. The system has 4x2226 (which is also negative polarity) and 4xLMS Ultra 5400 in separate enclosures and with separate DSP channels, so it's frustrating to factor in the negative and positive polarity every time I reset the system to start fresh. Would be nice if everything was in polarity from the get go so to speak.

    After having read through a lot of material on these forums as well as JBL's Bullitin on the matter + talking with Odd, it looks like 4343B with the charge coupled network are not negative polarity but a mix where the woofer is negative polarity while the rest of the drivers are positive polarity seen from outside the cabinet (meaning red on driver to black on speaker). Looking at the schematics he sent me all other drivers red terminals go to the black terminal of the cabinet, while the woofer is wired red to red and black to black.

    For others who might stumble upon this thread in the future:
    negative polarity = cone moves inward when a positive signal is applied to the red terminal
    positive polarity = cone moves outward when a positive signal is applied to the red terminal

  9. #9
    Senior Member grumpy's Avatar
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    For others who might stumble upon this thread in the future:
    negative polarity = cone moves inward when a positive signal is applied to the red terminal
    positive polarity = cone moves outward when a positive signal is applied to the black terminal
    might want to give that last line another look...

  10. #10
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    Done!

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