4333/L300 Network/Driver Polarity Question

[Chas]

Hi everybody,
I am in the process of breaking in my DIY 3 way system and have reached a point where I need some help.

If I interpret JBL polarity conventions correctly, I think that all three drivers are considered to be negative, the 2231A, 2420/2312/2308 and the 2405H.

Okay, so assuming this is right, if I interpret the 3133 network schematic correctly, it appears that the 2420 is wired with the same polarity as the 2231A, despite the fact that there is a second order filter (i.e. 270 degree shift) in there. Maybe because of horn length?

The 2405H looks like it's polarity is wired in opposite to the other two drivers.

Have I got this right? I have tried listening to various polarity combinations and I think I have got it right. :confused:
Charles.

[boputnam]

You got the network schematic transducer polarity read correctly, and each of those are negative.

Got any pic's...? :yes:

[Chas]

Thanks Bo, no pics yet, I have to borrow a digital camera. Another question: to those who use mirror image JBL 3 ways with the offset side mounted 077/2405. Do you have your tweets inside or out?

[Tom Loizeaux]

I believe 2nd order crossovers (12dB/ octave) produce a 180 degree shift.
In any case, JBL figured this all out and the wiring diagrams indicate the proper wiring...UNLESS you want the cabinet to "play forward". The only reason to want this is if you may be hooking these up with any other drivers that follow the other polarity convention. (most others, as well as most modern JBLs)
The right way to do this is to follow the polarity on the wiring diagrams up to the actual drivers. Then vreverse the leads so the black wires go to the red binding posts and the colored wires go to the black posts. You can check th polarity, at least with the woofers by briefly touching a 9 volt battery to the speaker inputs. Touch the + of the battery to a wire that connects to the red input post...the woofer cone should move outward.

Tom

[Chas]

Tom, of course you are correct, I had third order on my mind....I must have been under the influence from listening to some terrifyingly high SPL's on some Telarc CD's! I was physically shaking....! Scary stuff how transients are reproduced by these things.
Charles.

[boputnam]

Originally posted by Chas
...to those who use mirror image JBL 3 ways with the offset side mounted 077/2405. Do you have your tweets inside or out? The greatest (apparent) spatial separation would be for the UHF to be toward the outside of each cabinet. It isn't much, but you can convince yourself it improves imaging.

And, thanks, Tom. I was frequently puzzled by that 270-degree comment while mixing last night - I figured Chas meant 180. Had to be. So as Giskard might point out, the 2420 is acoustically out-of-phase with the 2231. But, we really don't need to get into all this again, do we? :slink:

[Chas]

And, thanks, Tom. I was frequently puzzled by that 270-degree comment while mixing last night - I figured Chas meant 180. Had to be. So as Giskard might point out, the 2420 is acoustically out-of-phase with the 2231.

I'm glad to help fill your time with my mental seizure....:)

Acoustically out of phase? Are you referring to phase or polarity?
I might be s*** disturbing here and being a JBL rookie, I don't want to rock the boat:wtf:
Charles

[boputnam]

Originally posted by Chas
I'm glad to help fill your time with my mental seizure....:) No, sweat. At times, I find myself thinking the oddest things whilst sitting out at the FOH board...

Oh - it's only that there's electrical polarity (i.e., both as designed in the transducers and as imposed by the network wiring) and then acoustic phasing, as you alluded to by the 270-degree comment, in your initial post.

[Tom Loizeaux]

In terms of 2405 positioning, I chose to put the 2405s to the inside of my speaker positions partly because I have them so far apart, there are hard walls just outside the speakers and I wanted to reduce wall reflections, and I didn't want the lenses interfering with the direct "line-of-sight" to the 2405 slots from my sitting position.
Just my thoughts.

Tom

[herve M]

I have just gone up an old pair of 4333a. I am always skeptic also on the polarity of the cables. If the diagram of jbl is read, the cables of colors go on + and the black cables on -? It is thus well the color on the black terminals of the HP and the black cables on the red terminals?

[boputnam]

herve...

I'm confused... :spin:

Red -> (+)
Black -> (-)

But, what do you mean by "HP"...? :confused:

[herve M]

Sorry, HP= transducer in french.

for jbl, terminal of the transducer: black=+ and red=-
And for cables ?

[boputnam]

Originally posted by herve M
HP= transducer in french. Ha! I thought you meant HansPeter... ;)

Herve, you're about to get confused, or confuse me! :eek:

JBL transducers are designed to be connected:

Red = (+)
Black = (-)

However, since many/most JBL transducers are reverse polarity, this will give a negative cone movement (cone in on positive signal).

Please explain more - what are you trying to do?

*****

NB: I noticed this in the manual from the Ashly XR1001, a wonderful crossover I've lately been using - first time I've seen a manufacturer aware of JBL's polarity convention... :thmbsup:

[herve M]

If the colors are respected, then the membrane of the low register is inward. I suppose then, as on the series 4400, which should then be reversed the polarities with the connector block of the enclosure.

[boputnam]

Originally posted by herve M
I suppose then, as on the series 4400, which should then be reversed the polarities with the connector block of the enclosure. My broken english is not this good... :rotfl:

I may still be confused - but attached is the 4412 network (excerpt) as example.

The LF 128H-1 is at top-right, and connected GREEN wire to Red post. However, look on the top-left and the GREEN wire is connected to the BLK input. Through the network the 128H-1 is "cross-wired" and runs positive in this cabinet. So, if you connect the 128H in any JBL cabinet, connect the GRN or GREEN wire to the Red post, and you are fine.

Any help?

[herve M]

OK, the 4333 is negative system .
amplifier red =black 4333
amplifier black= red 4333

[boputnam]

Originally posted by herve M
OK, the 4333 is negative system. :yes:

amplifier red =black 4333
amplifier black= red 4333 :no:

Unless you want that...??


JBL design is:

amplifier red = red 4333 :yes:
amplifier black = black 4333 :yes:

[Hofmannhp]

Originally posted by herve M
...................the color on the black terminals of (the) HP ..........

:smsex: .....try to find my black terminals.........negative.....or is it posible......no......also negative.

HP

(sorry Herve :) ...of cause haute parleur )

[DavidF]

I had trouble with understanding the 4412A netword design before (I use it in a 3-way design at home). Initially I thought the schematic had a typo for the enclosure connections, mixing red with black on the input terminals. I’ll take Bo’s comment a little further because the 4412A network is not the best example to compare to the older JBL models such as the 4333.

In the older models, I found a consistent pattern where you can follow the positive connection from the amplifier (Red or +) through to the the Red (+) terminal on the system box, which then flows through the crossover network to the Red (+) terminal on the JBL driver, or the to the female connection on drivers that use quick-connect type terminals. As Bo indicates, once the signal gets to the driver, earlier JBL convention had the positive signal to the Red (+) terminal on the driver cause the cone/driver to move inward towards the magnet, different from most other conventions that had the cone move outward.

The crossover connections from the network assembly to the individual drivers also follow a general convention with the solid-colored wire (green to low, white to middle, yellow to high, etc) to the Red (+) terminal of each driver; the black or black-stripped wire to the Black (-) terminal of each driver (green w/black stripe to low, white w/black stripe to middle, etc). These connections remain fixed at the driver-side connection regardless of intended polarity inversions for any particular driver within the crossover network.

There is an exception with more recent 4400 models, one example being the “A” model of the 4412 series of monitors. The original 4400 series are designated Negative Systems by JBL, meaning a Positive signal to the Red system input terminal will cause inward motion by the driver(s). On the “A” models, JBL seems to have intended to conform to the positive-to-red-outward-motion format. With the "A" model, the Red (+) system input leads to the Black (-) driver terminals and this is how they accomplish the "Positive System" format.

DavidF

[boputnam]

Originally posted by DavidF
... the 4412A network is not the best example to compare to the older JBL models such as the 4333. A very succinct offering, DavidF.

The only reason I used the 4412A - an otherwise random choice of the 4400-series - was that herve indicated he was doing someingthing with a 4400 series. We don't yet know what, or which one.

Recall something the long missing EarlK said "once a thread get's to page two, it usually sufficiently off topic..." (paraphrased, apologies to the originator...).

Continuing off topic, I've noticed another "convention" that is usually honoured on the older JBL networks schematics: On each pair of transducer leads, when the top wire of the pair is positive (i.e., "GRN", or WHT, or "YEL") the transducer is wired to run negative. When the top lead is negative (GRN/BLK, WHT/BLK or YEL/BLK) the transducer is wired to run positive.

Of course there are exceptions!! That's why it's a RULE!!

:nutz:

[herve M]

Originally posted by boputnam

JBL design is:

amplifier red = red 4333 :yes:
amplifier black = black 4333 :yes: [/B]

Boputmam, for my 4333:

amp red= 4333 red = inward woofer
amp red = 4333 black = outward woofer

Better choice ?

[boputnam]

herve...

The networks for both the 4333 and 4333A have the LF wired:

amp RED = network GRN = LF Red = inward woofer

That's how JBL designed it. :yes:

[herve M]

Everyone says that a woofer must always function "outward"?!

extrait from " JBL technical notes vol1 number 12B"
"Polarity conventions of JBL Trnsducers and systems"

"
If JBL negative convention loudspeakers are used, the required polarity inversion should be made at the loudspeaker's input terminals themselves"

[boputnam]

Originally posted by herve M
Everyone says that a woofer must always function "outward"?! :no:

Only what matters is that like-kind transducers all be phased the same.

All LF's - either negative or positive
All MF's - either negative or positive
All HF's - either negative or positive

Having one transducer out-of-phase with others of it's kind results in erratic cancellations / interferance patterns.

The design of the 4333, like many/most vintage JBL's, has the woofer NEGATIVE, and is designed to be:

HF - positive
MF - negative
LF - negative

If you decide to change the LF wiring, you need to change MF and HF, too, to maintain the cabinet phasing of JBL's design.

The excerpt from Tech Note vol 1 No. 12b refers specifically to applications in PA systems, where JBL advises cross-wiring for LIVE applications (where Pin2 is hot).

[herve M]

Thank you, boputman .:)

[herve M]

Thank you, boputnam .:)
You merites of the holidays for your patience.

:smthsail: :smthsail: