JBL 4343, crossover 3143 upgrade

[andychris]

Hello

I've got a pair of 4343B and I would like to upgrade the crossover, first by changing the different caps. But as I can see, there is a big 52uF caps on all the HF signal, is someone shoud know if it should be possible to change this thing and do something like the 4345 crossover where the signal of the 2420 and 2405 don't go through this big cap ? But maybie it's not interesting to do this ? Maybie the 52uF don't modify a lot the signal to the 2420 and 2405.


Thanx................

[Odd]

You'll find lots of info here (http://www.audioheritage.org/vbulletin/showthread.php?16951-4343-References-Thread) and here (http://www.audioheritage.org/vbulletin/showthread.php?31638-New-Charge-Coupled-Crossovers-in-the-house).

[andychris]

In fact you can bypass the 56uF for the treeble and compression signal. I've done it with a switch to control with or without and mesure the result with room EQ wizard, there is no difference.

Her is the schematic of my 4343B with bicable, not biamp.

56102

[georgebrooke]

In fact you can bypass the 56uF for the treeble and compression signal. I've done it with a switch to control with or without and mesure the result with room EQ wizard, there is no difference.

Her is the schematic of my 4343B with bicable, not biamp.

56102
Hi Chris,

thanks for the nice crossover diagram.
I have not (yet) bi-wired my 4343 speakers but I am interested in your conclusions about bi-wiring. In the past I have found that the benefits were very clear on low efficiency speakers.. where there was a considerable current carried by the low-frequency cable. However, with a pair of Klipschorns, (104db/watt!) I found pretty well no difference at all between bi-wiring and single-wiring. Have you come to any listening conclusions yet?

George

[andychris]

Hello

I didn't biwire them just to be in biwire. In fact I've got a MIT cable who's got a special network for treeble and bass, so I need biwire. But I can tell you that there is a little difference when you remove the biamp system on the 4343. The internal wires are really poor quality, all the wires are very long, and sometime the signal needs to go from the connectors to the filtre boxe, go back to the biamp selector, go back to the filter, go to the attenuator, go bak to the filter and finally arrives to the driver. I think the total lengh is about 6 meters !!

So I remove all the internal wire and biamp selector. Now the wiring is more simple, I've got 4 real speaker connectors and I can plug every cables I want. The sound result is not totally different, but I feel there is more bass, and treebles are more clean.

[Ian Mackenzie]

You are on the right track.

Some time ago l messed with all these ideas and it is fun to smarten up these legacy systems.
.
Overall the stock 4343 are a bit hot and brash sounding compared to the more contemporary 4344.

Even so l prefer the precision of the 4343 (cc1975) to the more mellow 4435 (cc1983) on jazz as do the Japanese audiophiles today.

If you go into a jazz bar in Japan the JBL 4343 institution.

In terms of progression for upgrading the 4343 are you still using the original diaphragms in the 2420?

While the upgraded crossover will make the system more transparent the limiting factor is the break up modes of the original compression driver diaphragm and the cone of the 2121 mid cone. The later model 4344 and more recent 4344mk11 used improved mid and HF drivers and the crossover voltage drives (slopes) were revised to account for the different performance characteristics of the drivers.

Its is not absolutely necessary to upgrade the drivers but it is going to be better money spent than on fancy cables.

You may also find that the upgraded crossover sounds better overall in full passive mode than biamping if you are using a PA style electronic crossover network ie the JBL 5235 or M552 or the Rane or Ashly units to biamp. The full passive mode will not have quite the bass definition and transient capability but if you are using a HIFi amplifier you may prefer this approach.



From my Samsung Galaxy.

[Rolf]

I upgraded from the original x-overs to CC charged x-overs. Huge difference. Much better. I bi-amp.