Polarity, again.

[DavidF]

Looking for some confirmation (or some enlightenment) from anyone who has some JBL LE5-family mids on the bench. I thought I had picked up on JBL standards on a few things, and felt I had a handle on the black-is-sometimes-positive issue. But now I am confused about drivers that use the quick-disconnect type terminals. I recently had a LE5-12 re-coned. When a gave it a brief test, I noticed that the positive terminal was different than all others I have on hand. At first, I thought this a goof but I realized this may be hard to actually do (reverse the terminal connections). Further browsing of stock JBL networks (Tech Sheets and some networks I have on hand) that use the various 5 inch mids with terminals (LE5-6,10,12, 104H, H-2 etc) I notice that anywhere the polarity is shown on the Tech Sheet, the solid-color positive-connect wire terminates in a male connector to match with the female terminal on the driver. The re-coned driver follows this convention and would therefore match-up to the polarity checks on the Tech Sheet networks. In all other models I have on hand, which I have no reason to they are not stock, I notice that the male terminal on the drivers is the positive terminal (positive connection from battery to male terminal on driver pushes cone outward).

Please, I am missing something here?

DavidF

[4313B]

Positive voltage to female terminal on the transducer causes inward cone motion. The female terminal on the transducer is "red".

[boputnam]

In all other models ... I notice that the male terminal on the drivers is the positive terminal (positive connection from battery to male terminal on driver pushes cone outward).

I may be confused by your post (and which is male/female you refer to...), but this quote / your report cannot be correct: Positive signal to positive terminal will make the cone move in. That is JBL convention, certainly for the vintage tranducers you are asking about. But your last sentence (the above quote) makes me think otherwise.

So, either you have mis-identified the gender, are holding the battery upside down, someone has futzed around with your cabinet wiring before you, or I simply don't get it!

At first read, I thought perhaps the LE5-12 recone kit had "updated" the polarity (as Giskard has pointed out happens to the 123A on recone). Of course, my use of "updated" is horribly insensitive on my part...

Give us another report, maybe with pics of the posts, side-by-side? And (very importantly...) what cabinet and network are you working with? The 4312 L/R is positive (odd, but true, and it used the LE5-12) Just a guess.

Alternatively, ignore all this hoopla, and merely take a AA and connect the + to Positive terminal and see the cone action. That takes away all the doubt (and if you're going cabinet positive, begin the wire-cutting and re-soldering to swap gender on them dang "quick" terminals... )

[Robh3606]

Well this will really mess with your head.

I have an original 123A not reconned and it is cone goes out with a positve voltage on the red terminal. Standard polarity.


104H-3 Positive voltage to the male is cone out like Rob says.

LE5-5 Same as 104H-3

2105H Positive Voltage on red terminal cone goes in JBL standard polarity.

Ain't this Fun

Rob

[DavidF]

OK, here is clarification of my issues… somewhat.

Assumed: Pro units (and spill-over into consumer) used Black to identify terminal where positive pulse would cause cone (diaphragm) to move outward. Assumed, again, that JBL would assign this with a positive (+) on schematics and would route a solid color wire to this terminal (black-striped of same color conversely assigned to Red negative (-) terminal. JBL’s bulletin reiterates this convention, a “Positive System” is that with positive pulse to red terminal resulting in outward motion. “Negative System” is that with positive pulse to Black (non-red) terminal resulting in outward motion. I am OK here.

Then I try to apply this to, for now, to two different systems and I begin to lose consistency in the process.

Consumer model L112:

System terminals Red for positive, Black for negative. OK, a concession to market convention in consumer products. Woofer 128H with Black positive terminal. Green wire feeds Black terminal as shown in the schematic below. This makes the system “positive” using a “negative” driver. Positive pulse to Red system terminal results in outward motion of woofer cone. With the Mid I begin to stray. The schematic shows White/Black wire feeding negative terminal with the signal from the circuit. OK, a common reverse connection for the bandpass circuit, or so I first thought. The female connector from the lead mates with the male connector on the driver, which is the “positive” terminal. Therefore, the signal feed from the crossover results in a “positive” connection with the Mid which is in phase with the woofer, contrary to what I thought by reading the schematic. So, I do not follow the schematic assigning the “-“ to the “positive” terminal of the LE5-12.

Pro model 4412A1

System terminal is Black for signal, Red for return. Solid green wire feeds signal to Black (positive) terminal of woofer under my assumed connection protocol. A “Negative” system feeds a “Negative” driver with the positive pulse resulting in outward motion on the woofer. However, the schematic below, as well as a factory circuit drawing I have, indicates that a positive pulse to the Red terminal will push the woofer cone outward. This means that the woofer is operating in a negative phase. Green wire to red terminal rather than Black (opposite my assumed convention)?

The schematic also shows the Mid to be a positive connection as with the woofer. This jives as the Black/White wire tapped to the Red system terminal feeds the male driver connector, or the “positive” terminal. This driver, also, is operating in a negative phase.

The schematic shows the tweeter with solid yellow wire feeding the positive terminal of the tweeter (confirmed that the 052 has two male terminals the smaller of which is the “Positive”). The yellow wire is tapped to the Red system return terminal (opposite my assumed convention) and this would follow the schematic indicating a “Positive” connection.

So, all three drivers are in phase with each other, but as a system, operating in negative phase. Really haven’t caught on to this quite yet.

I have one LE5-12 in very good shape save dimples in the dust cone that I thought I could match with a re-coned driver. That driver arrived back with a distinctly different surround (not glossy, or doped as the older surround appears) and, as mentioned, different polarity. A brown shoe in a black wardrobe.

It would seem JBL and Microsoft both suffer the bane of legacy in their products.

DavidF

[DavidF]

Tech Sheet for L112 attached.

David F

[4313B]

Hi Rob,

All three of your transducers are the same polarity. You applied positive voltage to the male terminal which is the "black" terminal so cone will move out. You applied positive voltage to the red terminal on the 2105 so the cone will move in. All the transducers in the photo are "traditional" JBL polarity. Apply positive voltage to the RED push button terminal or female terminal and the cone will move in.

I don't know about David's recent LE5-12 recone because I just reconed two LE5-12's and they are the same old "traditional" JBL polarity.

The LE5-6, LE5-8, LE5-10 and LE5-12 take the C8RLE510 kit and the 2105H, LE5H, LE5-3, LE5-5, LE5-9, and LE5-11 take the C8RLE59 kit. The polarity doesn't change between drivers.

[4313B]

Applying positive voltage to the RED terminal of the loudspeaker system will yield the following:

128H cone will move in since positive voltage is going to the RED terminal on the transducer.

LE5-12 cone would move out since positive voltage is going to the male (BLACK) terminal on the transducer.

044 diaphragm would move in since positive voltage is going to the female (RED) terminal on the transducer.

This might be of interest to some. The 044 follows the same "traditional" "JBL polarity standard" of "positive voltage to female (RED) terminal causes inward cone/diaphragm motion". However, the male terminal has a (+) mark stamped into the aluminum frame. If you hook up positive voltage to the male terminal with the (+) stamp next to it you will get outward diaphragm motion. For those of you with L96/L112/L150A systems you may want to try reversing the polarity on your 044 transducers so they follow the 4313 phase convention. See if you prefer the sound. The reversal can be easily done at the point where the leads to the 044 connect to the PC Board. For those with 4313 systems, you may want to reverse the leads going to the 066 to see if you prefer the L96/L112/L150A phase.

Anyway... it's all fun and games until someone loses an eye, then it's just fun...

[boputnam]

Assumed: Pro units (and spill-over into consumer) used Black to identify terminal where positive pulse would cause cone (diaphragm) to move outward.

DavidF: Thanks for taking the time to clarify your observations - very helpful. I am still reading - and re-reading - your post, but at first glance...

Your first premise is incorrect. The Red terminal on the transducers is the "positive" terminal. Positive voltage applied to the Red terminal will cause the cone to move inward (or "negative" to the industry standard). Swap your color expectations, and maybe things will be more sensical.

Bear-in-mind that it is common to cross phase transducers in the same cabinet of multi-way systems (i.e., two-, three-, four- or five-way). That is, in a three-way cabinet it is not uncommon that the engineers decided the LF and HF would be (say...) running "negative", and the MF would be out-of-phase with them and run "positive". Using the phase cancelling effects in areas of slope overlap between the transducers can improve imaging.

I'm going to just grab the schematics and try and decipher them for you...

OK got 'em now, and I agree with Giskard (to do otherwise, I might lose an eye... ). Looking at the L112 schematic, be very aware that the network switches signal path, and uses colored wire for convenience at the transducer end, to wit:

L112
LF: the 128H is negative, and is RED INPUT to GRN to (+) Red terminal = running negative

MF: LE5-12 is negative, and is WHT to Red terminal, HOWEVER the positive signal is pathing from the RED INPUT to the WHT/BLK lead to the (-) Negative terminal = running positive. Look carefully at the schematic and you will see what I mean.

HF: 044 is negative, and RED INPUT paths to YEL to (+) Positive terminal = running negative.

In my self-accused parlance, I refer to this as a "negative" cabinet - referring to the how the LF is running.

4412
Interesting - doing the same exercise, you can see the 128H here is running Positive (RED INPUT paths to GRN/BLK lead to Negative terminal). So, the 4412 cabinet is running "positive", just like it's predecessor the 4312 L/R which I have a pair of, and got me into this mess to begin with!

Time for the good ol' warning: If you're paring the 4412 cabinet most other JBL cabinets, you may have phasing issues.

[DavidF]

OK guys, one more shot and maybe I will shut up. Rather than try to overthink this matter, which is my problem to date, maybe I can shoot this comment out for rebutts. I now think my problem is not recognizing the use by JBL of negative phase as the "norm". I am assuming that since the Black terminal is, in negative mode, is the "positive" terminal which typically accepts the signal leg of the circuit. What I interpret from your responses (thank you by the way) is that signal path follows with red as hot, black as ground/return. JBL, in normal configurations, feeds the signal through the red terminal. As such a positive pulse will cause the driver to move inward. Therefore, all drivers operate in negative phase (the drum kicks, the woofer sucks, si?) The exception would be operating in positive phase for crossover summation effects or phase correction.

Am I getting warmer?

DavidF

[4313B]

Don has a response here that relates to this thread as well.

http://www.audioheritage.org/vbullet...p?threadid=477

"Therefore, all drivers operate in negative phase (the drum kicks, the woofer sucks, si?)"

Yes. In multi-way systems the phase of the transducers is adjusted accordingly by simply reversing polarity. From Don's post, JBL transducers were designed so that positive voltage to the RED or + terminal resulted in a rarefaction. If you want your older JBL's to match current standards simply switch the polarity on all the transducers. Bo and others have talked about having to do this when mixing JBL systems with other systems.

[martinleewin]

If JBL (and I suspect all Lansing products) from the vintage in question are phased to each other corectly, but "opposite" to the otherwise conventional and/or modern world... why should we go to the trouble of reversing all the wires inside the cabinet???
When it would be so much easier to stick a label on the cabinet termination indicating "Opposite of Conventional Polarity" and keep the vintage unit in 'stock' configuration to boot?
Understood; that combining multiple multidriver cabinets with some drivers employing switched phase will cause inter-cabinet cancellations and image-shifting if they are close enough to each other. Those who switch back such out of phase drivers for intercab compatibility should also note this change on the cab termination panel so that others will understand (and as a reminder to themselves) what the heck is going on.
I would inquire as to whether it is the voice coil termination or the magnet (or both) polarities which is "opposed" to the popular/modern convention just as a trivia question-- in case I am on Jeopardy and one of those answers come up under the category of "Unconventional Geniuses".
Notice how I avoided the words "positive" and "negative" so far in this message. The words are confusing, and thus counterproductive, if they mean different things to different people. Neither is there "right" nor "wrong". Only what works for them; and then what works best in a larger group situation. I hate to be politically correct-- it just worked out that way for this topic.
To make things worse!!! The electrical polarity conventions are "WRONG". . . at least if you ask a physicist-- who swears that ELECTRONS HAVE A "NEGATIVE" CHARGE... and your battery's (+) terminal is from where the electrons flow (on that last part we have agreed).
That is why I only tell customers things make them go "BATTERY(+) = OUT" {as the basic goal} and how to make that happen in the least problematic and most harmonious way. Then mark wires with a black pen accordingly.
Anything different {from historical or acoustic design origins} is "opposite" to the majority convention. LABEL it as "OPPOSITE" because it may not work best in combinations. Now feel free to experiment for what sounds best to your ear or test apparatus. I might end buying pieces of your customized array and should not have to trust your memory. All I ask is that you DOCUMENT your results for future clarity.
The only exception being dual series-facing subwoofers phased opposite to each other; then in or out becomes up or down?... east or west? I give up... how many subs do you really need, anyway?
Martin W.

[boputnam]

...that combining multiple multidriver cabinets with some drivers (and cabinets) employing switched phase will cause inter-cabinet cancellations and image-shifting if they are close enough to each other. Those who switch ... such out of phase drivers for intercab compatibility should also note this change on the cab termination panel so that others will understand (and as a reminder to themselves) what the heck is going on.

That's what I'm talking about

The rest has my head

[boputnam]

The only exception being dual series-facing subwoofers phased opposite to each other; then in or out becomes up or down?... east or west? I give up... how many subs do you really need, anyway?

Hilarious!

[martinleewin]

Well, Bo,
I didn't think I had to add AND CABINETS to "...some drivers employing switched phase will cause inter-cabinet cancellations..." because that is really a Duh! that everyone should know if they can pronounce the word "faze" in passing. Whole cabinet phazing is readily accomplished with the AA when you can see the cones move. A compression driver out of phase, especially one behind a lens, is a dirty lowdown sneaky trick by comparison. Because if, say a mid horn in 1 of 3 opposite phase, sounds good with that cab, a fully in phase parallel cab right next to it will shunt the overlapping mids in an undesireable east-west fashion.
I would expect Microsoft to design that "feature" into computer monitors they sell to specifically interfere with competitive side-by-side comparisons. But I'll bet all Bill's home speakers ARE ALL in the same phase.
Sure, it WOOD be nice if the manufacturer put a correct schematic on the termination panel. But they will just say "you should not buy any other company's speakers but ours" and slap a "no user serviceable parts inside" sticker on the front (if that is the access point) if too many users complained. Product liability risk issue solved. Hey, they put red AND black terminals on the panel... what more would you want? Did you read the manual? It tells you all you NEED TO KNOW to install THEIR speakers in YOUR home, doesn't it?
We who know better should not be guilty of the same disregard for proper labelling. We don't even have a 976-WHOCARES? hotline to handle the complaints.
What REALLY fazes me out is that I can't get my Mac with Internet Explorer and VB to get these silly smilies to work!
Martin W.
Wizard Labs