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Thread: JBL Polarity Convention

  1. #1
    Senior Seņor boputnam's Avatar
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    JBL Polarity Convention

    Hey...

    I don't know if the old Thread on this will be accessible, so until then I'm going to input what I've found, and what I've discovered.

    First things first, here's the Link to the JBL "Technical Notes Volume 1 Number 12B" that talks about this. Unfortunately this is undated but is seemingly circa mid-to-late 1980's.

    Link: http://www.jblpro.com/pub/technote/tn_v1n12b.pdf

    Note that NO LE-series nor AlNiCo magnet assembly drivers are discussed.

    My testing compilation will be posted. I will also copy/paste here some experienced responses from the most recent exchanges.
    bo

    "Indeed, not!!"

  2. #2
    Senior Seņor boputnam's Avatar
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    Transducer Polarity Listing - 18/04/2003

    Here is a compilation of my testing results so-far. Luckily, I have a number of projects in process!

    Tests were the 9-volt "click" test, applying the posts of a 9-volt to the corresponding posts on the transducers. Where needed, an alligator clamp bridge wire was used.

    Negative = cone excursion "in" on positive voltage. Industry convention is "positive" (cone "out"), or reverse of convention JBL used on most - but not all - vintage components.

    If you are pairing vintage JBL cabinets with more contemporary JBL, or ANY other brand of any age, the vintage JBL will be 180 degrees out of phase, resulting in complex frequency cancellations and poor imaging.

    ----------------------------------------------------------------------------------
    The following are all NEGATIVE
    Tweeters
    LE20, LE25-4, LE26

    Mid-range
    LE5-2, LE5-9, LE5-12

    Woofers
    LE8T-2, LE8T-H, LE10A (both 8 and 16 ohm), LE10H, LE14A, LE15A
    2213H

    ----------------------------------------------------------------------------------
    The following tests POSITIVE
    Woofer
    123A-1
    Last edited by boputnam; 04-18-2003 at 11:29 AM.
    bo

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  3. #3
    Senior Seņor boputnam's Avatar
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    an archived reply from "Mr. Widget"

    This was a recent very helpful reply posted on the temporary forum, with some replys to specific questions, too.

    From "Mr. Widget" - 14/04/2003

    Basically all JBL loudspeaker components and systems have been the reverse of the standard industry practice until the very latest models and systems. JBL has continued to produce components that will be used with it's previous systems like the 2235H woofers with the reversed polarity. As they come out with completely new systems they are being introduced with the industry standard cone moves forward with a positive DC voltage, but it is very confusing as in a complete system you may use newer speakers with one polarity and an older sub with the other polarity.

    "3) Working on a pair of Flair 45's (S8), they instruct crossing the outputs from the LX5 going to the N7000 network - why is this? Is the LX5 different polarity than the (older?) N7000? In the S7 (sans the N7000) the horn is red-to-red from the LX5."

    This is another animal altogether. This is a common practice in three way systems where to get the most accurate phase response you place the mid driver 180 degrees out of phase with the rest of the system.

    "4) How do all of you JBL'ers deal with this - especially when mating a variety of components and maybe even paring cabinets side-by-side?"

    It is a pain. I always check the woofers in my finished systems with a DC test to verify that I didn't accidentally cross a wire. With compression drivers, if it is JBL I assume it is reversed, if it is someone else's I assume it is standard.
    bo

    "Indeed, not!!"

  4. #4
    Senior Seņor boputnam's Avatar
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    and likewise from Tom Loizeaux

    From "Tom Loizeaux" - 14/04/2003

    When I wire up componants, I always check the woofer phase by touching a 9 volt battery to the leads. I then try to put my head between the woofer and compression driver to see if the sound comes from a spot between the componants. If in doubt, I switch the compression driver leads to see if it improves. Since I wanted the color-coded terminals and banana connectors to match, I've had to re-solder the leads inside my JBL cabinets to correct the factory phase.

    I get all my speakers wired in phase so I can switch amps, wires and cabinets and never worry about phase problems.
    bo

    "Indeed, not!!"

  5. #5
    Senior Seņor boputnam's Avatar
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    A comment on "correcting" JBL polarity

    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/
    bo

    "Indeed, not!!"

  6. #6
    Senior Seņor boputnam's Avatar
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    Galaxy Audio "Cricket" Polarity Tester

    Humbly recommended by Mike Caldwell of VintageAudio.com (www.vintageaudiosales.com), this handy little device provides fool-proof verification of cabinet phasing. It's not cheap, but neither are JBL components and neither are the phasing questions trivial to resolve. The "Cricket" tests transducers already installed in the cabinet, more thoroughly than the 9-volt click test. It has other applications as well, to check the polarity of your entire system.

    "Cricket" can be researched at: http://www.galaxyaudio.com/galaxy/Pr...l#TEST%20EQUIP - check with ElaineC there...

    And, the folks at Northern Sound and Light (http://www.northernsound.net/Sales/t...o/cricket.html) gave the best pricing I could find. They drop-shipped it too - saved time.

    I have no commercial relationship with either entity, and only recommend "cricket" as something that solved some questions I have, and looks to be VERY handy.

    With it, I found the 066's are positive - they wouldn't test well any other way.
    bo

    "Indeed, not!!"

  7. #7
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    Did you check all your 066's? Positive voltage to the red terminal on the 066 will cause the dome to move inward.

    The 066 is wired out of phase with the LF in the 4313B (12 dB/octave filter) and in phase with the LF in the L166 and L212 (6 dB/octave filters)

  8. #8
    Senior Seņor boputnam's Avatar
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    066's

    Looking at the 3113B network schematic from the 4313B, answers the question, I think.
    http://www.jblproservice.com/pdf/Net...%20Network.pdf

    In the 4313B, the 066 is indeed cross-wired. The Red input for the cabinet is connected to the YEL/BLK (negative) wire for the 066. I had thought the 066 is cross-wired to run "negative" to match the polarity of the LE10H - a common phasing for a 3-way enclosure. But, you say the 066 was wired out-of-phase in the 4313B. If the 066 is indeed negative, the cross-wiring will have it running positive - opposite the LE10H. The LE10H is negative, and in the 4313B cabinet is wired Red input to GRN (positive) wire for the woofer - so the LE10H is wired normally and running negative. The 4313B cabinet is factory negative.

    I had trouble "click" testing the 066 - I got uncertain results. I will check it again tonight with the "Cricket" which gives less ambiguous results.

    I don't have the schematics for the L166 or L212 networks, but would like to see them. Rolloff rate/slope shouldn't affect transducer polarity, but may have influenced network wiring design.

    My grab is that in the L166 and L212 the networks are wired different (and the woofer might be positive, unless it's an LE-series, in which case it is almost surely negative). Regardless, it is the network wiring that determines cabinet polarity.

    I'll yank the 066 out tonight, redo and confirm the tests. I did the tests last nite on the cabinet, and since I've switched the polarities/phasing in the cabinet, I cannot recall with certainty which way the dang 066 is now wired (although it is now running positive as is the LE10H)!

    "stay tuned..."
    Last edited by boputnam; 04-22-2003 at 08:47 AM.
    bo

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  9. #9
    Senior Seņor boputnam's Avatar
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    066 - negative

    I've checked some notes I have with me, and comparing with the 3113B schematic, the 066 would be negative, as Giskard posted.

    Negative transducer cross-wired gives positive result.
    bo

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  10. #10
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    Positive voltage to the red/female post on the LE10, LE5, and 066 causes the cone/dome to move in. No networks, just raw transducers. These are all what you call "negative" polarity transducers.

    In the 4313B the LE10 is wired "in phase" so the cone would move in, the LE5 and 066 are wired "out of phase" so their cones/domes would move out. The 4313B network employs a 6 dB/octave filter between the LE10 and LE5 and a 12 dB/octave filter between the LE5 and 066.

    In the L166 and L212 the LF is wired "in phase" so the cone would move in. The LE5 is wired "out of phase" so the cone will move out. The 066 is wired "in phase" so the dome will move in. 6 dB/octave filters are used throughout.

    "If the 066 is indeed negative, it is cross-wired and therefore running positive - opposite the LE10H, and not the common phasing for 3-way enclosures."

    "Rolloff rate/slope shouldn't affect transducer polarity."


    The filter slopes determine what phase, or polarity, will be used. I've never heard of anything called "common phasing for 3-way enclosures".

    "I'll yank the 066 out tonight, redo and confirm the tests."

    Cool, it sould be interesting. All my 066's behave according to the JBL convention, which is opposite the tragically mixed up and terribly confused "Industry".

    We all know black is positive and anything else is negative. I personally found that out when I was 5 and touched the exposed black lead of a wall outlet while grounded. YEAH BABY!!!

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    Wow, you beat my post by a minute. I keep timing out and getting disconnected while writing posts. Thank goodness for Ctrl-A, Ctrl-C and Ctrl-V.....

  12. #12
    Senior Seņor boputnam's Avatar
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    Negative is good...

    Thanks for all that - it confirms the compilation I offered starting this thread. Then, I was pretty confused about it all and had some re-phasing to do - QUICKLY!

    You raise a question on phasing: Does a steeper slope (12 dB/octave) always pre-determine the transducers be out-of-phase?

    And, the 3-way "convention" was something I was "told" and which had been born-out by most of the 3-way enclosures I tested. But, I'm gettin' smarter...
    bo

    "Indeed, not!!"

  13. #13
    Administrator Mr. Widget's Avatar
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    "I personally found that out when I was 5 and touched the exposed black lead of a wall outlet while grounded. YEAH BABY!!!"

    Thanks for posting this, it explains so much

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    No doubt!!!

    Glad I could clear things up Mr. Widget...

    "You raise a question on phasing: Does a steeper slope (12 dB/octave) always pre-determine the transducers be out-of-phase?"

    Often but not always boputnam... there's the 120Ti for instance, all transducers are "negative", all the slopes appear to be 12 dB/octave, yet all the transducers are wired "in phase" hence all their cones/domes would move in.

    As for being confused it's kind of a perpetual state for me. There's always the 044 with it's + cast into the frame right where the - terminal is... Sounds to me like JBL has confusion issues too...
    Last edited by 4313B; 04-22-2003 at 09:56 AM.

  15. #15
    Senior Seņor boputnam's Avatar
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    I've run into more people ignorant of this issue than those that are aware of it. And every one are adamant JBL fanatics with many different cabinets, and many of whom have built their own enclosures, and have phasing conflicts throughout.

    Maybe they have decided to ignore it, and avoid the costs of psychiatric counselling !

    I'm almost there, too...

    ...except for the astonishing acoustic benefits of correct phasing in multiple component configurations. Simply mind (and ear...) blowing.
    bo

    "Indeed, not!!"

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