Polarity and 4343 wiring

[John Nebel]

Bo,

Interesting. It can't open the directory. MS
doesn't bother with standards.

Does the complete file name work?

ftp://atlas.csd.net/jbl/JBL_pn_1.jpg

They are named 1-5.

John

[John Nebel]

Bo,

Just tested with the latest IE 6 and it works.

I'll e-mail Don and ask him if he wants them for the library. If he doesn't and you or anyone else can't get to them, I can e-mail, total size 1mb or so.

John

[boputnam]

Does the complete file name work?

ftp://atlas.csd.net/jbl/JBL_pn_1.jpg

Yea, John - perfect. Thanks very much, and I appreciate the posting of this info. Nice.



Also, I just futzed around with the ftp, and found that if entered with a closing foreslash, e.g.:

ftp://atlas.csd.net/jbl/

MS recognizes it. Bingo. I should have noticed that, but it was late (for me...) last night.

Got any more goodies? ??

[John Nebel]

Bo,

A few things and I'll put them up.

Also, Don can take them for the library if he
wants.

John

[Tom Loizeaux]

John,
Today those files opened!
Anything else on thec 4343 or studio monitor crossovers, phasing, etc. would also be appreciated!

Thanks,

Tom

[John Nebel]

Tom,

The 5235 crossover manual has a section on polarity and phasing.

http://www.jblproservice.com/pdf/Vin...5%20manual.pdf

The manual also has the RC values for the various plug-in cards so the 4343 variant may be put together easily enough.

A 5235 should be available for $100-$200 from a 'net search or on Ebay if you ever want to go that route.

John

[boputnam]

Hey, John...

This quote has been sticking with me:

Page 5 had an interesting caveat - clearly JBL thought 4-way design was hard to get right.

that is, unless, JBL do it.

JBL (or at least Margolis...) does think 4-way provides better accuracy (from page 1):

"... but because (the 4333A) only has three transducers, it is not quite as accurate as the four-ways."

That has certainly been my experience, too. But I don't think I'd try and design one.

This Pro-Note has been a real interesting read. Thanks for posting it.

[boputnam]

Hey, Tom and Rob...

Grist for the mill, here, boys! I hesitate to even post this, and restart the grind

I've not tried different slopes for different crossover points in the frequency range - never had want to do so.

- remember who wrote those words...?

Well, looking (yet again), at a very clean full-color copy of the 4345 brochure lately provided me, I note the 4345 employs two different slopes, as follows:

The active 5234A with 51-5145 card crosses over at:
290Hz using 18dB slope (versus 12dB for the internal network at same crossover point, see below).

The passive, internal four-way crossover crosses over at:
290Hz using 12dB slope
1.3kHz using 12dB slope
10kHz using 18dB slope

So, what's it all mean? Are you two right in a 18dB slope being out-of-phase from the same signal with a 12dB slope of same polarity? If so...

¿Why would the 4345 change phase of the LF when in passive mode?
¿What is the REAL polarity of the UHF?



NB: I reserve the right to delete this post until my time to do so reliquishes by natural causes...

[John Nebel]

Bo,

There was probably a lengthy trial and error process getting the placement of drivers on the baffle, the drivers, and crossover design matched up. If one had a lot of time and the right room it could be done, but it would only make sense for the cost of that process to be spread over many speaker systems.

The more I read these threads, the more I appreciate the difficulty of getting it right.

JBL did seem pretty definite that biamping 4343s and presumably the 4345s which came later was a good idea.

I've read articles to the effect that one should not try biamping at home, but the JBL situation appears different in that it
was designed that way.

There was an interview with Peter Walker of Quad an aeon ago in Audio Amateur in which I believe he counseled against biamping, but that was due to amplifier power issues which have likely been transcended by the immense power for handling transients in modern amplifiers.

John

[boputnam]

"Don't let the math get in the way"

Got it!

But "The UHF slope is actually 24 dB/octave" has me puzzled. Simply for clarity sake, howzit? Is my nifty brochure in-error, or is there something here I'm ignorant of...?

[boputnam]

Giskard...

Great post - thanks.

Gimme more... ?? I'm guessing the impedence of the transducer (2405) contributes to the increased rolloff? Close?

I am repeatedly stunned by the imaging and "accuracy" of the 4345 - I had expected much greater evidence of crossover points in the listening. Not so. The 4345 design overwhelms, and has ruint my sleep habits. As well, the TV simply ain't getting used...

But, you've been notably quiet on the "timing vs phasing" questions raised here. Let me phrase this clearly as I can:

¿Does the effective 24dB rolloff on the 2405 change the "effective" phasing so that as-heard the 2405 is actually out-of-phase with the 2421B (versus in-phase as per the schematic)?

I know, "don't let the maths...", but still curious

[GordonW]

Originally posted by boputnam
Giskard...

Great post - thanks.

Gimme more... ?? I'm guessing the impedence of the transducer (2405) contributes to the increased rolloff? Close?

Sort of.

What's actually going on, is that if you look at a graph of the frequency response of a 2405, you'll find out that it starts rolling off at about 6000-7000 Hz or so. The initial part of the rolloff (say, between 7000-3500 Hz) is about 6 dB/oct... and that, combined with the ELECTRICAL rolloff of the crossover, gives an EFFECTIVE 24 dB/oct. rolloff rate, measuring the output of the speaker PLUS the crossover.

In essence, the speaker is PART of the crossover network. Many great speakers are designed just this way... letting the driver act as part of the crossover, and therefore getting to use a simpler (and usually more transparent, due to less stuff "in the signal path") and less expensive crossover...

Regards,,
Gordon.

[boputnam]

Giskard, that is exactly what I guessed, as I considered all the posts and reposts over the past few weeks, and tried to incorporate it all into my understanding. Lucky for me, I worded the query in a sensible manner (and minded my syntax ).

And, GordonW thanks very much - I only lack good quality frequency response plots to visualize what we are discussing - but it makes sense.

[B&KMan]

Hello,
(sorry for my poor english: I'm french canadian)

Well your question is a big 100$ question. And I paid big time and money for the response.

I aquired my 4343 in used and many problem appeard on the start.
third part recone installed, cabinet dammage and wirring inconsistence...
and of course classical position of the dimmer for high drivers.

Well , i sit down depp in my chair and I start a bigest scientifict procedure.
I buy and studdy a reference material mesurement Bruel and Kjaer. Very more expensif of the any system...
Well, I pick-up the diagram of cross-over, read many forum information...
and finnaly I attemp to ask a response.

1--- Confusion of phase and polarity...

Many peoples write the subWoofer is inverted phase and all driver is foward phase.

--- the phase is rotary response in real and imaginary part of wave sound and flutuate depens on hz production. If you put phase meter and generate sinewave with x frequency the y frequency is different reaction phase.
The polarity is the way of flux electrical. If you put a mic with analyser, not significant difference in polarity good and false. but big difference in ear result.

just the Jbl factory have a data for interpreting the phase relation in polarity...
and determine who driver is out of polarity depend phase reaction in X frecquency.

I pick-up a Dual channel analyser Bruel and Kjaer (2032) for analysing signal...
B&K mic is diffuse field type and preamp. the built-in generator on Analyser produce many type of signal: for this test I choose the impulse pulse (very short in ms).

If you applied impulse signal into the driver : Normally ( if the polarity is good) the diagram is go foward (pressure signal) and back little more slowly (after cut signal). (the invert reaction is called rarifaction response)

this test is easy to applied with the big driver : just put small 1.5 v batteryin terminal for very short time and check if the cone is go front or go back ...
(attention the driver is not built for dc current so be-carreful do not test is very hight sensitive driver or you burn driver)
Unfortunately, For any small driver of compression driver the movement is non visible and impossible to determine the side.


In the laboratory test...

I unbuilt my 4343.
I check the polarity terminal speakers for good corresponding of the wiring diagram of the internal cross-over. And yes the black terminal is the negatif terminal and red terminal is positive terminal. in my version of 4343 (serial # 12654)
This test is easy and any ohm-meter to help to check any wiring confusion :
the negative wiring is direct with no resistance at any driver... Just positive wiring is treated by the cross over... just look the diagram. This rule is universal !!!

But the bigget problem and where the confusion is start, All driver is connected according to positive polarity. No exception !!!

So if you connect the Woofer in battery , the driver is go forward or backward ???.

Ok Ok OK , I continue my experimentation:
I check the polarity in all driver : all driver is pull out of speaker and tested individual : the BIG SURPRISE: all Red terminal Driver is NEGATIF terminal.

YES If you put impulse signal : you discovery the driver positif terminal is BLACK.

So the BLACK terminal of all driver is connected to positif wiring internal cross-over.

So I connected all driver in respect of polarity respons and I rebuild speakers.

Plug and play Speaker and AMAZING More 25% more details fast respond, elimination of box sound, the presence and transient is realy better and more realistic.

So you run in your way. But for me, the mistake of commun sense to match red wire with red terminal driver is start a big deception...

But, because this speaker is pass in many hands and probably reconing, you have nothing idea if the tecnician is inverse the terminal connector for build modern correlation in red and positive convention or just rebuilt in accordance of old JBL chart...

Just scientific test is reveal the real Situation. So in doubth Check around you if guy have instrumation for make test...

Best regards.

[boputnam]

Originally posted by boputnam
So, reading your most recent post, here's what you done:

2231's: (+) voltage to Red terminal = (-), and also factory. That is the GRN wire, correct?
2121's: WHT to Red terminal = (+), and also factory.
2420's: RED to Red terminal = (+), and also factory.
2405's: RED to Red terminal = (+), and also factory.

According to your post, you have connected the tranducers to factory spec...