JBL L112 - Crossover Confusion

[scubadude]

Ok, I did a little searching on this but didn't get all my questions answered. Hopefully I won’t confuse everyone. So, to get this twisted story rolling here is part one:
I have two L112s that I’ve been sprucing up. First thing I noticed when I took them apart was that they didn’t have the same xovers in them. Since then I bought two used ones which are in great shape and the L-pads are smooth and quiet. I will replace the old ones with them. During my research to buy the new ones I saw three types of xovers for JBL L112s which don’t look exactly the same, one of which is totally different (one of my old ones that I’m replacing). I had one xover that was built on a black plastic backboard (hereinafter referred to as blacky) and had a nice pc board for all the components. The other cabinet had an xover built on a brown pressboard material (hereinafter referred to as brownie) and did not have a printed circuit board but just had components jumbled together on the board. I thought brownie was actually a patch/fix job done by someone before I got the cabinets which is why I originally wanted to replace it to be original. But, after pulling them out I saw that ole brownie was actually a factory board (it also came from a cabinet with a much higher serial number). So that covers 2 of the three. The third I’ve seen is just like the black one here but one of the chokes was much larger (the choke at the bottom of the board). So, here are some pics I took of my two old ones:

[scubadude]

So with that said, has anyone has seen this in the past? Anyone know the diffeneces if any between these 3 xover configs? More to come...

[scubadude]

A little more info to add before I call it a night. I did some wire tracing and I suspect (to the degree of around 90% positive that) these speakers have been running with polarity issues. What would be a help is if someone could verify that the black striped wire for LF,MF, and HF are in fact supposed to be on the negative terminals of their respective xover connections. Also, on the LE5-12 midrange, which wire connector is positive, the male or female? And last, on the 044, there is a + molded into the aluminum housing on the back side where the tweeters male terminal is, is the positive wire from the xover to connect to this terminal?
Sorry for all the rudimentary questions. Problem is I have 4 xovers with three diffenent wiring configs and don't know which one to trust,,, in a nutshell, I've got a clustery situation on my hands. :blink: :blink: :blink:
I'll also try to search here for some old documentation that may have schematics. Thanks.

[Zilch]

http://manuals.harman.com/JBL/HOM/Technical%20Sheet/L112%20ts.pdf

[scubadude]

Thanks Zilch. I found this link too on the JBL site. The tech sheet you linked is what I really needed though. Figured I'd post this incase someone needed it.
http://manuals.harman.com/JBL/HOM/Owner%27s%20Manual/L112om.pdf

[taro]

Hi,

the larger (bass) coil at the bottom would be an air coil with the same 2.5mH value as the smaller iron coil but preferred for lower distortion, also more costly.
I have seen both types installed in L96/L112/L150A which have the same networks.

regards taro

[DavidF]

A little more info to add before I call it a night. I did some wire tracing and I suspect (to the degree of around 90% positive that) these speakers have been running with polarity issues. What would be a help is if someone could verify that the black striped wire for LF,MF, and HF are in fact supposed to be on the negative terminals of their respective xover connections. Also, on the LE5-12 midrange, which wire connector is positive, the male or female? And last, on the 044, there is a + molded into the aluminum housing on the back side where the tweeters male terminal is, is the positive wire from the xover to connect to this terminal?
Sorry for all the rudimentary questions. Problem is I have 4 xovers with three diffenent wiring configs and don't know which one to trust,,, in a nutshell, I've got a clustery situation on my hands. :blink: :blink: :blink:
I'll also try to search here for some old documentation that may have schematics. Thanks.

The "brownie" may be a handwired version of the L112 crossover, after all. You will have to match up the component values.

Follow the schematic posted by Zilch for answers to the driver hook up. The color-with-black striped wire runs back to the black terminal (aka negative) for each leg of the xover. The driver leads shown in the schematic should be hooked as shown by the arrows. "-----<" means to hook this lead to the male terminal on the driver. "------>" to the female terminal. So, the mid driver is wired opposite phase of the low and high by design.

DavidF

[scubadude]

Using the schematic posted by Zilch I was able to get to the bottom of this. The two crossovers I bought were wired correctly as was the old brown one. For some unknown reason all of the black stripe wires were on the positive terminals of my old black crossover. So, the speakers had been running out of phase. I never considered reversing the input wires on the rear of the speaker to see if it sounded better, I assumed the inside was correct,,, never again. To give credit where credit was due, I had to spend some time on the black crossovers to tighten up all of the push on terminals which were all loose IMHO. The brown crossover was all soldered and solid. I have one speaker completely rebuilt (cleaner L-pads and new xover, reconed in 1999 128H, used but mint LE5, and a clean 044) except for replacement of the foilcal. Not sure what adhesive to use for that. Thanks again for the input on this.

[scubadude]

Zilch, just curious, how did you get to that link on the Harman site? I can navigate to the owners manuals but not the tech sheet you found. Only thing I could do was replace the "l112" with things like "l150" to get different sheet.

[4313B]

So with that said, has anyone has seen this in the past?Oh hell yes! I've seen every iteration since they first rolled off the line.
Anyone know the diffeneces if any between these 3 xover configs? More to come...Yeah, some used older 0.068 uF transcaps, some used newer 0.01 uF transcaps. Some used an IC inductor on the LE10/128 and some used an AC inductor on the LE10/128. Some were hand wired and some were PCB. I personally watched one woman hand wire one in the early days.

Zilch, just curious, how did you get to that link on the Harman site? I taught him. Technically it's nobody's business but we provide links to it anyway. After all, this is the Lansing Heritage website...

[scubadude]

LOL, thanks Giskard. Everything is clear now. :D

[4313B]

LOL, thanks Giskard. Everything is clear now. :DOh good, that means you are tossing that stuff in the trash and building your own charge coupled versions with new components right? :D

Seriously though, just find a matched pair of networks and one should be good to go. It is kind of irritating to start pulling these things apart and running into unmatched pairs. Obviously the PCB version with the large AC inductor is the most desireable stock version.

[scubadude]

That's what I was thinking. So, it was out with the old and in with the new matched set. They don't have the large inductors but they are a really clean set, the L-pads alone were worth the purchase since the old ones were fairly oxidated.

[boputnam]

...The driver leads shown in the schematic should be hooked as shown by the arrows. "-----<" means to hook this lead to the male terminal on the driver. "------>" to the female terminal. So, the mid driver is wired opposite phase of the low and high by design. Uh, no. :scold:

The BLACK striped lead (???/BLK) connects to the Black terminal of the drivers in all cases. You will note this on drivers like the LE5-XX's which have the M/F connectors - the networks are pre-wired this way.

If I read correctly, your post is exactly opposite of convention (not withstanding the specific MF comment).

Also, to scubadude, the intended "POS" terminal of vintage JBL drivers is marked with a (+) and/or a red dot (even though these are the (-) post by current industry convention).

Here we are once again... :o:

[boputnam]

...For some unknown reason all of the black stripe wires were on the positive terminals of my old black crossover. So, the speakers had been running out of phase. No, someone rewired them to reverse the electric "phase" of the drivers' response. Vintage JBL drivers are "negative polarity" - cone in on (+) signal. Your seller apparently went to the trouble of "correcting" that, in the cabinet. JBL sez you can take care of this by connecting the entire cabinet Red to Black on the terminals.

If, as you say, all the connections were reversed, then the relative driver phasing was being preserved to match JBL design - that is, the MF was opposite the LF and UHF, as is common in 3-way configurations (although the group was overall opposite what JBL designed). You can see this on the L112 tech sheet - the WHT/BLK connector for the MF comes from the RED input lead, driving the MF "reversed" so that (+) signal will give cone out movement for the MF.


I never considered reversing the input wires on the rear of the speaker to see if it sounded better, I assumed the inside was correct,,, never again. You make a VERY IMPORTANT POINT. Buyers of vintage audio gear - in-particular speakers - should thoroughly check the driver compliment, network wiring and in-cabinet connections to ensure things are as expected. This is not always so.

There actually is no right or wrong, although this is argued. To honor the music as if someone was performing at the end of your room the LF cones should move out on (+) signal. However, I've run my JBL's "backwards" from industry convention - but true to original JBL design - for decades. You can reverse the cabinet hookups, if you choose. It is really only important that each cabinet in a stereo pair are identical, AND that you do not stack/pair these with non-JBL brands (which will result in cancellations). Most SR and pro-gear documents are full of "warnings" about this, to make sure Main "stacks" and monitor wedge groupings are of consistently polarity.

[scubadude]

Thanks Boputnam, hehe, yeah here we are again :D
I think what David said was correct but misunderstood. The factory wiring had the white/black striped wires female connector on the LE5s male connector as the ---< shows. I think the misunderstanding stems from the fact that the white/black wire connects to the male/neg side of the LE5 then goes to a terminal on the crossover marked negative which is how the average joe (like me) sees it. When in fact that negative midrange terminal is routed to the positive rear input via the Lpad and PC board which isn't noticed until one starts tracing back that circuit. You don't see that swap up on the schematic, only on the actual crossover markings. The terminals aren't shown on the schematic. So, the LE5 is out of phase with the LF and HF. Of course, this is all true if the LE5 negative is indeed the male, there are no red dots or anything on the LE5s I have (four of them) compounding the confusion, I'm trusting from another thread on this site that the females are positive, males negative on the LE5s.

My big problem was that the handwired xover was in the vintage factory mode but the pc board model had been reversed as you said, so they were out of phase up to now with regard to the other speaker. I read about the mids possibly being 180 out of phase on the 112s but until you look at the schematic then the crossover it isn't all that clear, but they are. To make matters worse, the 044 has a + stamped into the casting where the negative terminal is. Still waiting on the verdict for that one. I hooked up following the schematic and JBLs original wiring and connector scheme thinking maybe the diapram was install backward and that I could trust the terminal gender to set things straight.

[DavidF]

Uh, no. :scold:

The BLACK striped lead (???/BLK) connects to the Black terminal of the drivers in all cases. You will note this on drivers like the LE5-XX's which have the M/F connectors - the networks are pre-wired this way.

If I read correctly, your post is exactly opposite of convention (not withstanding the specific MF comment).

Also, to scubadude, the intended "POS" terminal of vintage JBL drivers is marked with a (+) and/or a red dot (even though these are the (-) post by current industry convention).

Here we are once again... :o:

Thanks for the correction, Bo. Quite right. The point was meant to be that the mid driver polartiy should be opposite of the others and avoid going into the whole negative-is-positive in the JBL world again. As long as the orignal crossover-to-driver connections are respsected then you should be OK.

DavidF

[DavidF]

...To make matters worse, the 044 has a + stamped into the casting where the negative terminal is. Still waiting on the verdict for that one. I hooked up following the schematic and JBLs original wiring and connector scheme thinking maybe the diapram was install backward and that I could trust the terminal gender to set things straight.

Follow the schematic and don't try to equate the "+" indicator on the driver to how the schematic reads in terms of "+" or "-". The connection from the male terminal on the 044 follows back to the black input terminal.

David.

[scubadude]

Sigh,,,,, I think I'm suffering from bi-polarity...
I'm still not sure if I got it right. I'll get some kind of readable documentation of my wiring and post it for review. Thanks again :)

[4313B]

I guess I don't understand what the problem is.

The wht/blk wire gets the female faston and the wht wire gets the male faston. The yel wire gets the male faston and the yel/blk wire gets the female faston.

[boputnam]

So, the LE5 (MF) is out of phase with the LF and HF.Yes, by this design, and is a common topology for a three-way system.


Of course, this is all true if the LE5 negative is indeed the male...I'd worry less about "sex" and more about polarity... :rotfl: Truly, if you use the connectors pre-fitted on the crossover leads - like they do in the factory - the drivers will all get hooked-up as intended. (see Giskard's post above, and quoted here...)


To make matters worse, the 044 has a + stamped into the casting where the negative terminal is.If it is stamped (+), why are you characterizing it as "negative"...? Again, I think you might be too focused on what the pre-wired connectors are, versus where they are meant to connect.


I guess I don't understand what the problem is.

The wht/blk wire gets the female faston and the wht wire gets the male faston. The yel wire gets the male faston and the yel/blk wire gets the female faston.Yea, bingo.

JBL, as we have reminded ourselves, designed things in one room, but planned for things to be assembled in another room - call it an assembly line - where people not trained in crossover topology or acoustic theory were tasked with assembling things unformly to spec. This is called Quality Assurance / Quality Control (QA/QC). JBL could not risk things be be assembled wrongly, so the QA/QC focussed on the wiring from the crossover. So long as it was color-coded correctly, THERE WERE NO DECISIONS ON ASSEMBLY. It was truly "plug-and-ship".

[scubadude]

If it is stamped (+), why are you characterizing it as "negative"...?


Ok, I'll try to make sense of my take on this question:
As far as the 044 is concerned, I'm confused becuase the yellow/black that is connected to the xovers negative faston HF output has a female faston on the other end that connects to a male faston on the tweeter that has a "+" stamped on it. Plus is positive but it's the negative wire connected to it. In contrast, the green/black LF wire connects to the xovers negative input and the woofers negative input. So, ???/stripe is negative for the woofer but ???/stripe is positive for the tweeter. Therefore one convetion is followed for the woofey and different one for tweety, so the consistency varies among drivers in the same cabinet. I'm only talking about connections from the xover fastons to the driver, no other normally unseen criss crossing on the pc board to rear terminals. It seems that there are varying layers of inconsistency through out, I think. Inconsistency on where the polarity switch occurs, sometimes on the driver, others on the rear terminals or pc board. I think I may change my handle to "Wingnut" :screwy:
I'm going to prepare a PPT to fully illustrate my wiring, will take some time but may be a reference for future neophytes :applaud:

[scubadude]

PS: Don't get any ideas, I'm the official wingnut. That handle is officially copywrited on this site :thmbsup:

[Zilch]

Sorry, prior use:

http://audioheritage.org/vbulletin/showpost.php?p=25091&postcount=16

[License fees now due and payable.... :p ]

[boputnam]

As far as the 044 is concerned, I'm confused becuase the yellow/black that is connected to the xovers negative faston HF output has a female faston on the other end that connects to a male faston on the tweeter that has a "+" stamped on it. ...Scubadude...

Without reading the rest of your post, it occurs to me that some moron mucked around inside these cabinets, right? Surely, they switched the "faston" connectors to work with the wiring the seller needed to feel "smart". That is why I suggested ignoring the connectors, per se, and focus on the wire colors/striping, which JBL installed. RARELY are these switched at the crossover connections, but you should have a lookie and see if there is obviously redone soldering there. More commonly, the wires are clipped, stripped and different "fastons" attached at the transducer end, only.

Make sense? Follow the network schematic and trust that JBL marked the intended (+) terminal on the transducers with either a RED dot, or a "+"...

[boputnam]

Follow the network schematic and trust that JBL marked the intended (+) terminal on the transducers with either a RED dot, or a "+"...IGNORE what the present connectors are, and see if you can achieve the connections as JBL designed.

Looking at the schematic, starting bottom of cabinet to top:

LF (+) = GRN wire
LF (-) = GRN/BLK wire

MF (+) = WHT
MF (-) = WHT/BLK

HF (+) = YEL
HF (-) = TEL/BLK

Anything with a BLK strip or BLK solid goes to a (-) transducer terminal. Solid non-black colors go to (+) terminals.

Are we helping you...? :o:

[scubadude]

Yes, you guys are definitely helping, thanks for sticking with me on all of this and sorry to be so confusing. The fact that we are dealing with the physical (the actual xover), the virtual (the schematic), the oddities (multiple versions of the xover some of which had been rewired), and this darn 044 with the + on the negative side,,,,,,. I'm thinking I need some vintage of another sort at this point, now I know you west coast guys can relate to that, 01' Sin Zin it is :)
Seriously, I am putting together a quick powerpoint to show what I've got, will post when done. Good news is my next two projects are simple (famous last words...). My sister's L60ts rotted surronds and one of my 4408s which a cat attacked. The 4408s still live here, that cat has been exported.

[edgewound]

I'll add to the confusion here.

The 128H woofer in the L112 is a "positive to black" terminal woofer. As JBL often stated in lit, "positive voltage to the black terminal will result in outward cone movement...



Anything with a BLK strip or BLK solid goes to a (-) transducer terminal. Solid non-black colors go to (+) terminals


So that preceding quote is, unfortunately...incorrect....Sorry Bo:o:

Therefore, on the crossover schematic the black/grn wire goes to the black terminal on the woofer; solid green wire goes to the red woofer terminal.

The other drivers are pre-polarized with the crossover wire connectors as Giskard pointed out...with the polarity of the mid driver reversed for phase of the crossover....just hook'em up how they are, provided they havent' been tampered with. The negative terminal on each driver should be treated as if it were red...and would receive the solid color wire. Notice on the schematic that midrange "wht/blk (-)" wire traces back to the red input, and the "wht(+)" wire traces back to the black input. The wiring in this case takes into consideration the crossover phase relationship.

On the input terminals of the speaker system, positive voltage to the black terminal will result in outward cone movement. I know it's wierd....but that's the way JBL did things with the exception of a very few models.

This decades long confusion is the reason JBL has phased in the "positive to red" convention over the last two decades with their newer driver and system models.

[boputnam]

I'll add to the confusion here.:yes:


The 128H woofer in the L112 is a "positive to black" terminal woofer. As JBL often stated in lit, "positive voltage to the black terminal will result in outward cone movement...That is completely true.

But edge...

Almost all the vintage JBL tranducers are as you describe - i.e., of negative polarity (+ signal to red = inward cone movement; the 123A-1 is perhaps the sole exception in this vintage, as it is a "positive" driver).

When you open a vintage JBL cabinet the woof is connected non-BLK to Red terminal, that is, solid color (non-BLK) to Red - always. I don't work on raw drivers like you do, but I have opened dozens of un-tampered cabinets and it's always the same - absolutely consistent. The scheme is steadfast. Any wire with anything "BLK" goes to the black terminal.

These vintage cabinets "sucked", if you will, which is why JBL issued that Tech note suggesting users might reverse connections to the back of the cabinet, so the cabinet performance will conform to "revised" ;) industry practice.

Connecting a 128H as you recommend will absolutely do what you say - but that was not the original build.

[edgewound]

:yes:

That is completely true.

But edge...

When you open a vintage JBL cabinet the woof is connected non-BLK to Red terminal, that is, solid color (non-BLK) to Red - always. I don't work on raw drivers like you do, but I have opened dozens of un-tampered cabinets and it's always the same - absolutely consistent. The scheme is steadfast. Any wire with anything "BLK" goes to the black terminal.



Bo.....that's what I said too....at least I thought I did.

[boputnam]

Bo.....that's what I said too....at least I thought I did.OK. Whew...

This:
The 128H woofer in the L112 is a "positive to black" terminal woofer.

So that preceding quote is, unfortunately...incorrect....Sorry Bo:o:

was at-odds with:


Therefore, on the crossover schematic the black/grn wire goes to the black terminal on the woofer; solid green wire goes to the red woofer terminal. this last quote, being a correct statement.

As designed, the cabinet would be connected with amp output (+) connected to the Red cabinet terminal, which traces to the GRN wire to the 128H (+). Thus, the woof is going to have cone "in" movement on (+) signal (i.e., it is a negative polarity transducer as you noted).

As we know from later dated JBL Tech Notes on JBL's (unique) polarity convention, JBL has since recommended that this vintage of cabinet be connected with amp (+) connected to Black cabinet terminal so that the woof will have cone "out" movement on (+), as is current industry convention. This "reversed" cabinet connection will reverse the absolute motion of all the transducers, while maintaining their relative polarity (crucial for matching the crossover design).

The most important thing here, faithful readers, is to follow the wiring color code on the network schematic - only by these connections will you maintain the crossover (and cabinet) design characteristics.

[opimax]

OT a little, pardon me

I got a little confused when changing XO on my 250

What about on a 4 way XO ? maybe another day :)

Someday I need to verify (understand) the original 250 and the ones Guido built to make sure I do have them hooked up properly...

I understand enough to keep my woofers all firing out at the same time but not checking individual connections at the XO

Mark

[brudha]

:yes:

When you open a vintage JBL cabinet the woof is connected non-BLK to Red terminal, that is, solid color (non-BLK) to Red - always. I don't work on raw drivers like you do, but I have opened dozens of un-tampered cabinets and it's always the same - absolutely consistent. The scheme is steadfast. Any wire with anything "BLK" goes to the black terminal.

This wiring diagram of the L220 woofer (LE14H) (http://www.audioheritage.org/vbulletin/showpost.php?p=51342&postcount=5) looks to be the opposite of your statement. It shows the Green/Black going to the RED post and the solid Green going to the BLACK post. I could have sworn when I took them out that the Green/Black was on the Black post. Now I'm all confused........

[4313B]

Here's a couple more to add to the fun:

L112 and L220 (alnico)

[brudha]

Here's a couple more to add to the fun:

L112 and L220 (alnico)

Those pics still show the black-striped wire going to the black post though.

What's the deal with the L220 LE14H being the reverse, in that, the green/black goes to the RED post? Is it possible it's a typo in the original manual? Like I said, I'm reasonably certain the green/black was on the black when I removed them. Now, upon reinstall I'm not sure how to proceed..........

[4313B]

Is it possible it's a typo in the original manual?Absolutely.

In any case, you should be able to tell which way sounds correct.

I'd start with solid green to the red terminal on the LE14H.