Polarity and 4343 wiring

[Robh3606]

Sorry but the best I can do is uninformed!

Simply the crossover cards are either 12db or 18db on the 5234 so I am not sure what the crossover does?? Does it maintain the proper phase relation ships between high and low pass or invert like you would a passive crossover so you would have the same phase relationship between drivers as the passive crossover??

I use a 24dB L/R set-up to. I have my drivers in phase. I know the crossover does not invert phase from high to low pass. It has the option to do so if required. My crossover does not have a delay option so I can't fine tune or compensate for driver distances IE horn loading of the bass or compression driver. Theoretically without path differences you would be one cycle out of phase at the crossover point.

I am a babe in the woods with active crossovers very much on the learning curve, hope I am correct hope this helps

Rob

[Robh3606]

Hey Rob

Is there a 1 cycle delay with no path diferences??

Rob

[Tom Loizeaux]

I hope these will be my final words on wiring my 4343s.
I realize, now, what the schematic calls for and believe JBL was correct with their color coding.
I also feel the JBL intended that these studio monitors be used either in the INTERNAL mode (4-way passive crossover) or EXTERNAL mode (bi-amped) with the cabinet being driven by outputs from two amps being fed by an active crossover at 300Hz, in the case of the 4343, and that a 12dB/octave be used. JBL probably hoped that their 5234 or 5235, with the appropriate cards be used, or that another crossover brand be used - having a 12dB/octave slope.
It seems to me that correct polarity, as set up in the 3143 internal crossover, expects the low pass crossover to be a 2nd order, 12dB/ octave slope with a 180 degree shift. I also suspect that this 3143 crossover uses the physical set-back of the 2420 to acheive phase in this design. By using a different slope on the low pass crossover point you are changing the phase relantionship of the woofer to the rest of the componants, particularly noticeable between the woofer and the mid bass driver!
So, if I use a 24dB/octave slope (360 degree shift), I will not provide the required 180 degree phase shift and, in reality, would be running the woofers 180 degrees out of phase with the rest of the drivers! I can either switch the wires to the 2231, or use my active crossover's delay (phase adjustment) to correct this effective 180 degree disparity!
I think I have this right (finally) and I wonder if this makes sense to those who might know more about this then I.

Looking forward to your comments.

P.S. I truly think I'm done with this issue and promise not to continue to chase this...unless, of course, someone shines a new and compelling light on this issue!

Tom

[Tom Loizeaux]

I hope I didn't scare off any responses to my last post. I AM curious about responses to my idea that the 24dB crossover shifts the woofer polarity from what JBL expected...etc.
My comment about being done whit this was really ment to say that I'm going to try not to generate more questions about this because I feel a little guilty about stiring up some of this confusion.
I am looking for truth and would like to hear from others about whether I've found it on this issue.

Thanks,

Tom

[Robh3606]

I have always been fascinated with the whole phase issue. Between the the different crossovers orders 1st-4rth and types Butterworth L/R and there effects, then there is baffle position and path lengths for horns. Complicated in the sense that there are many things to consider. Especially when you are trying to coble a set of speakers together from scratch. That phase switch is the way to go!!

I am curious about responses to my idea that the 24dB crossover shifts the woofer polarity from what JBL expected...etc.

Makes sense an extra 180 degrees of shift so you have to reverse and there is no reason to have them out of phase unless path length differences cause a null at crossover. I would still like to know if the 5234/35 inverts phase on its outputs. I think it does as it only makes sense to keep the same passive crossover phase relationships.

Rob

[boputnam]

Tom and Rob...

Just returning from a trip, and trying to catch-up on your discussion. There's a nearly parallel Thread on the Technical Help forum that is about to converge with this one...

From there, as per usual, Giskard posts the most remindful:

Utilize the phase condition which yields the most natural reproduction.

...but that doesn't answer your question on the active crossover sending out-of-phase signals to the LF and HF (2-way).

From Rob:

On the M552/553 you can invert phase on High Pass outputs.

I wonder whether JBL incorporated this option into their later-model active crossovers because of their legacy polarity convention...?

Let me see if I can wire-up that Galaxy "Cricket" to answer your question(s). I believe I can insert it pre- active crossover and check for phasing effects (w/ and w/o the actives), but this is will take making some cables and such. I have both the 5234A and the 553, so if I get it done, it might be useful. I regrettably won't get to this until closer to the weekend, and by then you may have formed your own crossover company!

[boputnam]

Rob...

...I am not sure what the (active) crossover does?? Does it maintain the proper phase relation ships between high and low pass or invert like you would a passive crossover so you would have the same phase relationship between drivers as the passive crossover??

I'm not sure this will relieve some of the mystery, but both these schematics are portrayed in 4-way, passive mode. That is, the internal switch converting the cabinet binding posts (inputs) from bi-amp configuration to internal crossover is shown in the the "internal crossover" setting. The 3145 is a bit more clear to see this, and if I'm reading it correctly, the phasing of the cabinet is unchanged whether bi-amped mode (and using the 5234A), or not.

So, in the case of the 5234A active crossover, the 3145 schematic suggests LF and HF outputs are in-phase. This confirms my hunch, and I think I will forego the Cricket test.

[Robh3606]

Hey Bo I was typing this when you were doing yours. You beat me to the draw. I see your point.


"On the M552/553 you can invert phase on High Pass outputs."

I took another look you change phase on all outputs.

"I wonder whether JBL incorporated this option into their later-model active crossovers because of their legacy polarity convention...?"

Could be for the most flexability.

"Let me see if I can wire-up that Galaxy "Cricket" to answer your question(s). I believe I can insert it pre- active crossover and check for phasing effects (w/ and w/o the actives), but this is will take making some cables and such.

I have been thinking about that. Could be I am making this harder than it is. This stuff always mess's me up.

When you switch the Biamp switch you keep the same polarity on the woofer so it already is correct. So all you are doing is splitting the signal at the appropriate frequency and slope. So why would the crossover have to invert the phase?? As long as the slopes are the same all should be well.

Rob

[boputnam]

Hey, Rob...

I took another look you change phase on all outputs (552/553).

Interesting, and potentially very useful measure of flexibility!

When you switch the Biamp switch you keep the same polarity on the woofer so it already is correct.

... and as well, the phasing of the MF, HF and UHF are unchanged whether bi-amped/external or 4-way/passive.

So all you are doing is splitting the signal at the appropriate frequency and slope. So why would the crossover have to invert the phase?? As long as the slopes are the same all should be well.

Agree. I've not tried different slopes for different crossover points in the frequency range - never had want to do so. I have paid more attention to the potential benefits of "null" or boost points at crossover (vis-a-vis David F's post, 07-18-2003 10:18 PM, Technical Help), but not the use of different slopes.

[John Nebel]

This is somewhat off-topic but touches on the issue of biamping 4343s. Doesn't seem to deserve a new thread.

I put an old Pro Note prepared by Garry Margolis up on

ftp://atlas.csd.net/jbl

I'd forgotten that JBL said the 4343 had the same bandwidth at a 4350.

Their comments on bi-amping are on page 4.

I think the hand-written numbers are the prices for the components of the 4343.

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

John

[Tom Loizeaux]

John, I just tried your "atlas" link and none of the files (pics) would open. ?

Tom

[Earl K]

Hi John ( Tom )

Those JPEGs opened within my browser - from that ftp file server. ( I use MS Explorer - 5.0 , on a Mac that is running system 9.2 )

<. Earl K

[John Nebel]

Tom,

They are standard JPEGS on a bog standard Unix server
and have been tested with

(1) Mac OSX 10.2, Netscape 7
(2) Win2K, Netscape 7
(3) Mac OS9, Netscape 7
(4) Mac OS9, IE 5
(5) WinNT, IE 5

Computer nerds do this out of habit.

In each case one could click on the image file name or icon,
depending on the variant and the page would display. The images are scaled to display normal size on a 1280x1024
monitor.

Which error message do you get and what is the OS/browser combination?

Computer nerds also ask questions like that.

John

[boputnam]

Which error message do you get and what is the OS/browser combination?

Here's what my repeat experience has been, but me thinks it is related to a popularity contest!

Oh, and running XP Pro and IE 6.0.2800 sp2.03, but as I say - I think it's traffic...

[boputnam]

Rob and Tom...

Just had a thought, while out walking the dogs this evening...

I don't know where/why you got into that lengthy discussion about active crossovers and polarity - but it occured to me that the color of wire coming out of the passive crossovers and their relations to phasing might have in-part been involved.

My grab is, the networks were not designed to change phasing, per se. Decisions about phasing were part of the cabinet design, and to add to what has been posited here, the networks were merely wired with the appropriate colors and stripes/non-stripes to facilitate factory assembly.

So, with all transducers negative, (+) to all the Red terminals would have all transducers (-). But, as example, if the MF was to run out-of-phase from the LF (for whatever imaging reason), and the LF was running (-), the leads coming to the MF from the network would be installed such that the Red Input on the cabinet would path through to a striped wire for the MF, so that during factory assembly the MF striped lead could be blindly connected to the Black terminal, yielding a (+) phase. This is what the like posts from Giskard were illustrating.