New 4345 L pad wiring

[Ian Mackenzie]

Given the recent apparent confusion over the polarity of the woofer relative to the mid, horn and slot its worth spending some time understanding these diagrams.

Referring to the equivalent 3145 schematic you will note the polarity of the terminations to the mid/horn and slot are inverted after the L Pad.

What does this mean? Inverting the polarity will result in the driver voice coil pushing the cone outward rather then inward per JBL convention. This applies to the positive swing on an a/c sine wave as well as the simple 1.5 volt battery test.

http://www.jblpro.com/catalog/support/FAQJBLSpecific.aspx


JBL did this in the4345 design due to the way the passive woofer to midrange filter works and results in a smoother response transition at the woofer / mid range crossover point. It is important to note the mid, horn and slot must all have the same wiring polarity to the crossover.

For how to wire up the 4345 clones floating around recently please find below some pics and graphs.

I will post a pic over the weekend of a correctly wired L pad

[JBLCanuck]

Nostravia!
LOL! It all looks like Russian to me.
I think I need you to draw that up with crayons & then maybe I'll be able to understand it. :D:D

[Ian Mackenzie]

Okay,

While the camera battery charges let talk about the way these L pads work.

They are not a conventional Pot in that there are two wire wound elements, one is about 0-8 ohms measured from tabs 3 & 2, and the other is about 0- 40ohms measured from tabs 1 & 2.

This is known as a constant impedance attenuator for a know load, in the case 8 ohms.

Its important therefore that it be wired up the right way (it can only be wired up one way..more on that later).

If you go crossed eye looking at the schemtic and then the graphic of the L pad don't worry.

What bis important is that the earth (ground side) of the circuit always goes to Tab 1, and the active signal size goes to tab 3. The output to the load is taken again from tab 1 and the active signal from tab 2.

Fortunately most L pads have the numbers engraved on the tabs.

In the mid position the resistance between tabs 2 & 3 is about 4 ohms while being 19 ohms between tabs 1 & 2. The net result is about an 9 ohm impediance as seen by the crossover using a known load of 8 ohms

Below is an image (enhanced) of a 4345 clone L pad.

This is not wired correctly in consideration of Back should be ground (-) and should go to tab 1.

The Red wire is shown going to tab 3.

The output to the drive is taken from Tabs 1 & 2 where tab 1 is red (+)and tab 2 is black (-).

The output wiring is correct. But unless the constructor was calling the active (hot) signal from the crossover black the L Pad may not work properly because of the series resistance in the hot side of the circuit.

In this circuit the postive or red from the amplifier is the red wire (hot) all the way to the L pad connections. The polarity is reversed only on the output of the L pad. This also makes it hard fior anyone else to work out how the drivers should be phased but shit happens. (There also a resister on the Horn L pad output)

The bottom image is the correct wiring looking at the L pad from the rear.

The red wire (hot signal) from the crossover goes to tab 3 and the back (earth) wire goes to tab 1. The wire from tab 2 is black to the black terminal of the driver and the red wire from tab 1 goes to the red terminal of the driver.

[Ian Mackenzie]

On enlarging the image of the incorrectly wired L pad above it can be seen the horn L pad is also wired incorrectly.

The output to the driver is taken from tab 1 & 3 while the signal from the crossover is connected to tabs 1 & 2.

I guess its been like that for the past three owners and will probably stay that way based on recent events.

[Robh3606]

I guess its been like that for the past three owners and will probably stay that way based on recent events.

Good attention to detail.

Rob:)

[Ian Mackenzie]

CSI...JBL!!

So much for the criminal minds to mess with this stuff.(only kidding)

The fix is actually straight forward and I would suggest the constructor got confused with the wiring to and from the L pad.

[BMWCCA]

The fix is actually straight forward and I would suggest the constructor got confused with the wiring to and from the L pad.
And I would suggest nearly everyone gets confused by these "contributions". You need to either become a better photographer or get a better caption editor. ;)
In the photo of your "correctly" wired L-pad, I can't see the shaft so if you're really looking at it from "the back" your example is reversed from the schematic you posted in post #1. So why are you so smug about finding what may not even be a flaw in "my" 4345 wiring? According to the diagram you drew, from the back terminal "1" would be the first of the three going in a clockwise direction and terminal "1" gets the tandem (-) connectors continuing to the speaker (-) terminal. Of course Giskard's schematic shows the (-) from the amplifier going to L-pad terminal #1 and the wires double-up at that terminal and the second wire goes to (+ red) at the speaker terminals—just like mine (the "bad example") are wired. Your drawing shows the (-) going to (-) at the speaker. Ummm . . .

So, if I could ask you all for a rare moment of clarity, is your "correct" photo really taken from the "back" (not shaft side), or is your drawing (diagram) of the correct wiring wrong?

You all seem to be having a good time poking fun at those you've booted from this site who aren't even here to defend themselves—or their work—against your accusations. You can't determine if "my" wiring TO the L-pads is simply done so colors would be matching from the box terminals to the speaker terminals, or not. I can, and I've done the "battery test". But if even a dumb-ass like me can tell your wiring protocol doesn't match from one post to another, why do you think there's so much confusion on this issue? And to whom should we attribute the cause of that confusion?

If I'm wrong, I'm humble enough to admit it. Are you?

If you quit spending so much time ridiculing others you might be able to post something us dummies can understand. And you all are supposedly the smart people here! I'm told the newbies like me are the ones who demonstrate the poor decorum.

For posterity, unless it gets changed or deleted:
http://audioheritage.org/vbulletin/attachment.php?attachmentid=37365&stc=1&d=1235069195

[Ian Mackenzie]

I have edited this post to add new pics for clarity athough it as quite obvious in the prior images.

For those who may wish to compare this to stock 3145 crossovers and the wiring please refer to the 3145 pictorial thread.
The stock crossovers the output of the L pads was looped back to the crossover boards and the polarity reversed on the board then looped back to the drivers. see here for details: http://www.audioheritage.org/vbulletin/showpost.php?p=142747&postcount=5

Go to this thread and refer to all the codes for what wire goes where:

http://www.audioheritage.org/vbulletin/showthread.php?t=13930&highlight=3145+pictorial


To avoid all the extra cabling with diy networks I simply reverse the polarity at the L pad tabs (as can be seen) and send the signal direct to the drivers. As I stated earlier to ensure polarity continuity with the rear binding posts on the back of the enclosures its important to maintain color coding of the wiring right through the crossovers to the L pads. The reverse the polarity after the L pad and only at that point. It is important that Tab (1) is always referenced to the input (-) or Black terminal to ensure correct operation of the L pad (no series resistance back to the amp).

This will make it less confusing and ensure the Lpads are wired up correctly and that the drivers have the correct polarity continuity overall.

Ian

(The Cape Cod coffee mug is my authentification cc2004)

[Ian Mackenzie]

Based on the arse about / backwards wiring scheme in the clone above I did some measurements (std 8 ohm load test jig) and compared it to the correct wiring per the schematic.

Depending on the positon of the Horn L pad the horn will run about 2.5 DB hotter then it should render ing the foil cal markers useless.:banghead:

Under the actual real load impediance of the driver there maybe other issues relating to accuracy of the voltage drive for the horn.:blink:

[BMWCCA]

No need to worry about it any longer. I know Dave admitted to you that he made the mistake at that L-pad. I have corrected it. I've also mounted the CC crossovers inside the cabinet on the "floor" and switched-ouy the Neutrik plug for two pairs of dual-banana binding posts on a plate that allow for removal with four screws from the outside for access to the 9v battery. And yeah, I still have some Krylon Semi-Flat black.

I learn something new every day, on a good day. I said if I was wrong I was humble enough to admit it. Now that I know the terminal numbering system for the L-pad, I can see Ian was right about the wiring being backward on that L-pad. Robert did mention the adjustment was a bit touchy, and I wasn't aware that swapping wires at T1 and T3 made any difference on a constant-impedance L-pad. I do now, thanks to Ian. It seems to be working fine for me now. (There is/was no change in polarity or phase. ). It was actually an easy fix since Dave mounted the L-pads on a board attached to the baffle with fixed studs so the foilcal doesn't need to be removed. He thoght that one out well!

I still don't believe the question was ever answered concerning whether or not the polarity is reversed in the schematic simply because of the slope in the LF circuit when not bi-amping, or if it is still necessary to reverse it with the Ashly XR1001 and its 24dB slope when bi-amping. I'm not opening that can of worms again since there seems not to be a consensus and everyone gets all pissy about it. My drivers are all in phase . . . unless I don't want them to be. ;)

If anyone cares, my much-maligned 4345 reproductions are working great and making their owner very happy. Having them apart in the living room today was just another chance for them to impress me with the quality of construction in the cabinets and the pristine condition of the drivers. :thmbsup:

[subwoof]

And if they are working correctly and make the owner happy is that not the end result ( desired ) ?

yes.

And reading the many posts by ian I find his many small typo's and english ( kings, criminals and colonies ) grammer mistakes that are not caught / corrected by his browser somewhat like speedbumps in the dialog. Hey dude - work on it OK ?

In the *hundreds and hundreds* of cabinets I made for the install / SR / club customers my rule of thumb is ALWAYS reverse the phase / polarity / convention ( whatever the PC word is this month ) at the actual components terminals *if needed*.

That way there is NO guessing where it was / not was reversed anywhere else. Because so many cabinets went to SR companies that used a mix of manufacturers ( yes diehards, there are others ) it was understood that with JBL components the rule was black NEVER went to black.

"top to bottom, left to right, alphebetical order, dark to light, low to high, black never to black with JBL" repeat it back. again.

I used twisted pairs that always had a black lead ( like jbl with their black stripe ) so it made sense. Keeping a standard meant repeat sales and NO TECH SUPPORT CALLS at all hours.

And this was way before internet / cell phones / etc...:)

sub

[Robh3606]

My drivers are all in phase . . . unless I don't want them to be. ;)


That is the correct phase on the woofer when bi-amping with the Ashly. The drivers will sum properly that way using the Ashly or any other 24db network.

Glad you are enjoying them.

Rob:)

[Ian Mackenzie]

I am glad you are enjoying them and that is worked out:)

Ian

[BMWCCA]

As Subwoof wrote, black doesn't go to black.

I mentioned this in another thread but I've moved the CC crossover to inside the cabinet, mounting it in rubber shock-mounts to the cabinet floor. I'm using a bi-amp-style twin dual-banana binding post input cup mounted to a board on the "original" crossover T-nuts and retained the original JBL input "hole" in the back of the cabinet. Four screws gets me access to the 9v battery on the CC boards. I did have to put "black to anywhere-but-black" on the 2245, as Sub says, but at least now it's all internal and the binding posts can be connected to the amps red-to-red, black-to-black. I now have 1.5v battery + to red binding post at input cup giving outward cone extension on both cone drivers. Now all I need for posterity is Giskard's foilcal to point out LF and HF connections with the correct 290Hz crossover point. Hopefully the end to much confusion that might even help our Canuck friend as he nears the point of making noise.

[subwoof]

The "Black to Black" issue was for my own wiring convention and did not always relate to similar JBL factory boxes that started then ( cabaret for example ). I bought a handful of 1000 foot rolls of 14 and 16ga twisted pair wire at an auction and used them for many years.

JBL played this internal wiring convention game at the beginning of the cabaret, thru the early install boxes and the first cheapo MI ( later MR ) cabinets. Every revision had different crossovers and different wiring colors like JBL was using different vendors yet again. ( they did with the cabaret wood boxes - some fell apart ) With no internet or tech print sheets available ( we were not service dealers then ) it was confusing at best.

Of course now that the "revised" transducer convention is used by JBL for the new generation Nd magnets ( but only some! ) and some other install ferrites, it's another can of worms...

Read the label and use your trusty battery or phase checker...

sub

[Ian Mackenzie]

I now have 1.5v battery + to red binding post at input cup giving outward cone extension on both cone drivers. Now all I need for posterity is Giskard's foilcal to point out LF and HF connections with the correct 290Hz crossover point.

Have look at the JBL link I posted in the other thread about their wiring convention. If you connect a 1.5 volt battery directly to the transducer with the negative battery terminal to the black terminal of the transducer and the positive battery terminal to the red terminal of the transducer the cone will move inwards and NOT outwards.

Try it and see for yourself. Clear as Mud right.

Meanwhile back at the ranch the polarity of the wiring in the stock factory 4345 was reversed after the L pads on the mid, horn and UHF for the purposes of the ensuring the correct crossover transfer function of the woofer and mid cone in full passive mode.

If someone decides to clone their own 4345 and use other than the JBL specified wiring and alternative biamp filters (other than specified) there will no doubt be confusion.

Unless someone else is able to examine and confirm what has been done on site or well documented images posted in a thread its a waste of time discussing it in terms of arriving at a definitive answer.

I would point out the standard of literacy per population in the USA is the lowest of any developed country( meaning a lot cannot read) . You mix this up with reversed conventions that are borrowed or should I say stolen from elsewhere and this makes reading a schematic awkward at best!

[Robh3606]

One last time or I am going to find a pig to kill. Where's that leg bone??

There is no ulterior motive here. The point is to hook them up correctly to get the most out of them.

This is really pretty simple. The top of the cabinet is all run in phase. That doesn't change.

The woofer can be wired the same or opposite of the rest of the drivers. How that is wired is determined by the crossover used. Using the original network as referenced, wired with a Positive of the Amp on the Positive of the speaker. The correct wiring on the woofer is:

Standard passive network is +

Standard JBL Active using a 5234/35 with the correct cards +

DIY with a 24db network - wiring opposite the previous 2


You have to remember phase to the speakers is relative. You can switch it either way and it doesn't matter as long as it's the same to the pair in a 2 channel set-up. What's really important is to get the driver phasing correct in the cabinet. If you don't the drivers will not sum properly through the crossover region. There is a reason you switch the woofer phase in the DIY set up using the 24db network. That is so the woofer sums properly with the 2122 using a 24db network. That driver to driver phase is not arbitrary. There is only one way for it to be correct.

Rob:)