PDA

View Full Version : JBL Polarity Convention



boputnam
04-18-2003, 12:00 PM
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.

boputnam
04-18-2003, 12:23 PM
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

boputnam
04-18-2003, 12:29 PM
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.

boputnam
04-18-2003, 12:36 PM
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.

boputnam
04-18-2003, 12:49 PM
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/

boputnam
04-21-2003, 09:25 PM
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/Products4.html#TEST%20EQUIP - check with ElaineC there...

And, the folks at Northern Sound and Light (http://www.northernsound.net/Sales/testequipment/galaxyaudio/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.

4313B
04-21-2003, 11:59 PM
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)

boputnam
04-22-2003, 09:15 AM
Looking at the 3113B network schematic from the 4313B, answers the question, I think.
http://www.jblproservice.com/pdf/Network%20Schematics/3113B%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..."

boputnam
04-22-2003, 10:12 AM
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.

4313B
04-22-2003, 10:13 AM
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". :p

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!!!:p

4313B
04-22-2003, 10:16 AM
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.....

boputnam
04-22-2003, 10:35 AM
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...

Mr. Widget
04-22-2003, 10:45 AM
"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:D

4313B
04-22-2003, 10:47 AM
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...

boputnam
04-22-2003, 11:16 AM
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 ! :eek:

I'm almost there, too...

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

Mr. Widget
04-22-2003, 11:33 AM
Not all systems are as revealing, but in any good system correct phasing is huge. I remember 30 years ago when I mis-wired a mid driver and heard the improvement first hand from reversing it's polarity. Years later I found out why!

Unfortunately crossovers shift phase and there is nothing we can do about it. A first order network shifts phase the least, but they don't always work well, especially with JBLs.

4313B
04-22-2003, 11:48 AM
My first "known" polarity "issue" occured when I was building a custom LE14H/LE5-9/044 system. Once completed I A/B'd it with a pair of L96's and a pair of L112's. My "creation" sounded weird, bizarre, even frightening! A call to Northridge resulted in the "fessing up" concerning the incorrectly stamped + on the 044 frame :p

I changed the leads to the 044 and all was good.

In the Loudspeaker Components Series Instruction Manual from the late 70's JBL actually detailed the wiring of a phase reversal switch for use when wiring systems to facilitate A/B comparison of phase response.

boputnam
04-22-2003, 12:10 PM
My "first" was pairing some strongly recommended 4313B's with other cabinets - the result was awful. I almost turned the 4313B's away.

Instead I got the network schematic and after a few hours of dissection and testing, I grokked what was going on. Some quick Polarity Triage remedied the acoustic malady (for this install).

Now I know that "Negative is Good".

Jakob
04-23-2003, 03:26 AM
Geeeh! Now I'm really confused. I started out by wondering if the 2405 J is negative. It's not on JBL Pro's negative list, but so are the 2405H, and some of You clames it's the same speaker?! And what about when I use it with a 18 dB network, how do I connect it correctly? hmmm...
I'm also confused about the phase of the mid's in my L150's Should they be connected in, or out of phase?
Any help appreciated!

4313B
04-23-2003, 07:18 AM
Hi Jakob,

The LE5 in the L150/L150A is wired out of phase with the rest of the system. The female terminal on the LE5 is RED.

As for connecting the 2405 correctly, according to JBL, phase doesn't count for much up in the range the 2405 operates but you can always use their fancy little phase reversal toggle switch to A/B and get it right.

boputnam
04-23-2003, 09:21 AM
Hey, Jakob...

I read on one other of the JBL .pdf's that the "H" designation signified 8-ohm, the "J" 16-ohm. I have seen that borne out on the few tranducers I have of like number and have H and J of them, but don't personally know the 2405.

You can see on that JBL Tech. Bull 12B partial listing of transducers that most H, and J of the same model are the same polarity. So, if it is only the question of impedence, my guess is the 2405"J" is negative, like the "H".

I've been warned about doing the 9-volt "click" test to compression drivers - it may overdrive it. Maybe someone (Giskard...?) knows if this warning need be heeded, or not.


"Negative is Good"

4313B
04-23-2003, 09:45 AM
Well I was going to "recommend getting a dedicated 12 volt dry cell battery to test your polarity. It has to be a dry cell, they dump the necessary current required to clean out all the electrons that routinely hide out in voice coils." but then I realized someone might actually take me seriously...

9V is a bit much for smaller coils. It's "fun" and "ok" for abusing the 3 and 4 inch coiled LF transducers. 1.5V to 3V should be more than enough, and don't use dry cells at all.

Mr. Widget
04-23-2003, 10:28 AM
I've always used a weak 1.5V battery and it never fails to move the coil.

As far as cleaning out those pesky stuck electrons, DC only works to a point. I find it is better to use a good clean 60Hz signal directly out of the wall.:D

Tom Loizeaux
06-23-2003, 08:15 PM
At the risk of beating this in to the ground, I would like a confirmation on this polarity question.

My take on the JBL schematics is that the red input terminals send the + voltage to the crossovers, showing the signal the caps/inductors before it sees the drivers. This "crossover first/driver second" seems to be the recommended "direction" for proper results. So, to bring my JBL speakers (vintage) in to modern polarity convention, (+ voltage to red input terminal on the input board or crossover moves speaker forward), I would only have to switch the wires at each driver. Correct?
Thanks,

Tom

boputnam
06-23-2003, 08:29 PM
Correcto-al-mundo! Loosly translated that means correct all over the world... ;)

ONLY at the drivers. And, by doing EACH transducer opposite of it's factory wiring, you'll be honoring the phasing between the transducers as intended by JBL engineers.

Think of the route of an active crossover - signal leaves preamp/EQ and courses through the active crossover then to the transducers. You could wire the transducers any way you want, but the networks need "see" the signal before the transducers.

But - again, unless you're pairing those gorgeous 4343's with a positive cabinet, it won't matter one Hz. But you will be in-phase with hearing aids! Ha!

boputnam
01-22-2004, 03:57 PM
from one of our International Correpsondents... ;)

MJC
01-25-2004, 08:44 PM
Originally posted by Giskard
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.
That is what I came up with when I checked a spare 066, and 2105

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.
After reading this, I changed the leads on the (3) 2105s I have in the 3 L212s I built a 1 1/2 years ago so the mid range would be out of phase with the 112a and the 066. But when I checked the original pair of L212s that have the LE5-9s(that have male/female connects) the yellow/black leads, (-) according to the schematic, were connected to the male terminal. So If red is the same as female, then black is the same as male. So, the LE5-9s were wired in phase with the LF and HF, just the opposite of the above statement. So what gives?

boputnam
01-25-2004, 09:28 PM
Ahhhh....

JBl would not make it so obvious as that! :scold: And, I need to approach this non-sexist... :o , using only Red and Black.

We need to decipher the impacts of the network schematic. Funny things go on between the cabinet connection posts and the transducer binding posts...

The one Giskard knows this network better than I - and perhaps better that it's design team! :rotfl: I'll have a look at it tomorrow, but (at great personal risk!!! :duck: ) the HF is connected opposite polarity the rest of the "team". According to my read of this schematic (posted by Giskard) the MF is phased with the UHF. It's the HF that's on it's own... :hmm:

4313B
01-25-2004, 10:04 PM
Ok, let me think about this again.

RED input terminal to RED wire to #1

RED #1 to #3 to WHITE wire to RED post on 112 driver. Cone would move in.

RED #1 to #6 to YELLOW/BLACK wire with FEMALE end to BLACK/MALE tab connector on LE5 driver. Cone would move out.

RED #1 to ORANGE wire to RED post on 066. Dome would move in.

Guido
01-26-2004, 04:49 AM
Originally posted by boputnam
Ahhhh....


Nice to have you back :duck:

boputnam
01-26-2004, 08:12 AM
That is my read, exactly.

I last night thought of annotating the schematic, as follows...

4313B
01-26-2004, 08:45 AM
Ok, so is there still a problem with my initial statement?

boputnam
01-26-2004, 09:12 AM
I sure don't think so.

This whole issue makes me :nutz: sometimes...

4313B
01-26-2004, 09:15 AM
Alrighty then! :nutz:

You guys sure had me going late last night. I was so tired I couldn't see straight. :p

boputnam
01-26-2004, 09:32 AM
Originally posted by boputnam
I'll have a look at it tomorrow... :hmm: I seem to have been feeling the same way. :rotfl:

MJC
01-26-2004, 08:50 PM
Originally posted by Giskard
Ok, let me think about this again.

RED input terminal to RED wire to #1

RED #1 to #3 to WHITE wire to RED post on 112 driver. Cone would move in.

RED #1 to #6 to YELLOW/BLACK wire with FEMALE end to BLACK/MALE tab connector on LE5 driver. Cone would move out.

RED #1 to ORANGE wire to RED post on 066. Dome would move in.


I can see now that I temp. confused myself with this entire thread. I HAD the "new" L212s wired correctly. Then I changed the connections on the 2105s and then had to change them back after reading your statememts above.

4313B
01-26-2004, 08:56 PM
Ok, so nothing was wrong with my initial post then right? It's just a bit confusing.

How is the system sounding these days?

boputnam
01-26-2004, 09:12 PM
Originally posted by Giskard
How is the system sounding these days? Ahh, the soothing wisdom of the Giskard. :coolness:

At the "end of the day", the sound (to your ears, MJC) is really all that matters... :yes:

But "where" in Nevada? Pahrump? :rotfl: I spent nearly a decade in ol' Elko, and loved the place. But that was before Clark County stole the 702 Area Code... :mad:

*****

Oh, and...

Originally posted by MJC
I ... confused myself with this entire thread. ...troubles me a great deal. I stumbled into this near netherworld unknowing, but it explain a phasing conflct that arose from my pairing 4312's and 4313B's. :scold: No can do. It had never occurred to me there would be phasing issues within/between the same brand of cabinet, but alas, my ears told me :yes:. So, here we are, and many have/are struggling with attempting to resolve phasing issues that arise where least expected. :duck:

Don - I do promise to compile my findings on this, both by cabinet and individual transducer (even more important because networks are the final judge of active polarity). Getting closer...

MJC
01-28-2004, 08:03 AM
Originally posted by Giskard
Ok, so nothing was wrong with my initial post then right? It's just a bit confusing.

How is the system sounding these days?

The system is sounding really great, with 2 subs, put one surround box is still short a 112a. I haven't seen any 112a for sale in almost a year.
In the next couple of months I'm going to build 2 more boxes, mirrored image for the 2 main speakers. I'm curious as to how much of an improvement there will be for 2 channel play.
And add .0056uf polystyrene pypass caps to all the 066s.

MJC
01-28-2004, 08:24 AM
Originally posted by boputnam
Ahh, the soothing wisdom of the Giskard. :coolness:

At the "end of the day", the sound (to your ears, MJC) is really all that matters... :yes:

But "where" in Nevada? Pahrump? :rotfl: I spent nearly a decade in ol' Elko, and loved the place. But that was before Clark County stole the 702 Area Code... :mad:


I'm in Douglas County, 10 miles south of Carson City. I have to go to Elko next week to do an install job- replacement doors, not HT:banghead:
Although there are quite a few more people in and around Elko, especially going toward Lamoille, there is still alot of things they don't have, like a Home Depot.
I was over by your way 2 weeks ago, working at Clear Lake and in Redding.

boputnam
01-28-2004, 08:47 AM
Originally posted by MJC
Although there are quite a few more people in and around Elko, especially going toward Lamoille, there is still alot of things they don't have, like a Home Depot. Good fortune appears in the least expected ways (and places...) ;) .

4313B
01-28-2004, 09:05 AM
Originally posted by MJC
I'm curious as to how much of an improvement there will be for 2 channel play.Ok, you have two "stock" so you can A/B right? I'm currently designing new enclosures for my L212's as well.

As soon as you stop looking for 112A's they should show up ;)

boputnam
03-09-2005, 06:38 PM
Oh boys-and-girls, here it is, the post you've been thirsting for! Excerpted from a pm I received...


Hey Bo, I'm like a 40+ yr old kid in a candy store.:bouncy: Got my (L100) babies back today. OK, Here's what I found out. The earlier model, #237954A the one with the push connectors has a woofer 123A-3. This is the same for the later model #269707A with the twist connectors, 123A-3. ...my son even sent me the owners manual which came with the later speakers. It says:

"Special Note: To maintain consistent polarity with other JBL models, current L100's (commencing with serial number 47100 and easily identified by the foam ring surrounding the HF direct radiator) are reversed in polarity with respect to earlier units. If early and current L100's are utilized in the same room, the early units should be connected "out of phase" with the current L100's. Thus, if the wires from the negative terminals of the amplifier are connected to the black input terminals of early L100's, the negative wires for current L100's should be connected to the red input terminals."

So, all my tedious posts and nagging pursuits of this legacy are vetted. Vetted by the L100, dammitt!!! :banghead: We here long ago surmised polarity issues were the reason for the switch to the 123A-3 (a negative transducer) from the 123A-1 (an unlikely positive transducer) in later model L100's.

Hat's off to "invstbiker". Nice! :applaud:

And, interestingly, JBL think's it unneccesary to cross-wire AT the transducers (inside the cabinet); JBL suggest doing it at the cabinet binding posts is sufficient. Okie-dokie then. The old AC-DC thing...

Mr. Widget
03-09-2005, 06:49 PM
Bo,

It is apparent that you may now retire from the forum. Your mission accomplished. That nagging at the back of your mind finally quieted.

Congratulations! Few of us so plainly reach the end of The Path... the End of Suffering. Tell us what it is like under your Banyan Tree.

Widget

boputnam
03-09-2005, 07:32 PM
Tell us what it is like under your Banyan Tree. Thanks, friend.

It is exactly like 4345's running off some oh-so effective QSC's and a nice analogue EQ barely affected by the Adcom pre-amp...

:wave:

My best always to you, and Ms. Gadget...