4343b-Bi-Amping with 5234 / 250 Hz?

[4343b_bremen]

Hello..

I got a 5234 acrtive crossover with 2 x 250hz division..

The internal crossover of 4343b (3143) cuts the bass at 300 Hz.. so the 5234 will separate only a 'third' kower. Do you think this is of importance for the performance of the bass-midrange 2120 ?

The advantage is saving one big capacitor for the whole MHT-Unit and the inductor for the bass speaker in signal-flow..

Andreas

51022

[Robh3606]

Try it. I biamp my 4344's and they sound great!

Rob:)

[HCSGuy]

I will preface this with the disclaimer that I have not bi-amped my 4343's, so my input is purely theoretical. When you switch the speakers to bi-amp, you bypass both a 52mf capacitor and a 2.9mh inductor on the HF side, and the 5.4mh inductor on the LF side. However, the bypassed components on the HF side, I think, function to attenuate the HF side, not as a HighPass crossover. the HighPass crossover is not defeatable, so if you use a standard 250hz card in the crossover, you will have two HighPass crossovers in the circuit (one active, one passive) and one LowPass, in this case at slightly the wrong frequency, and your frequency response hole will be even larger than you thought. JBL's factory bi-amp solution was the 52-5140 crossover card (labeled 4343 LowPass), which did not have a HighPass section - it passed HighPass through to the outputs, though I don't know if it had any attenuation. I think it was 275hz LowPass only, 12db/octave. In your case, you could approximate this by splitting the fullrange output of your preamp and sending one leg through the crossover for the LowPass (woofer), the other straight to an amplifier with a gain control for the HighPass (MF/HF/UHF).

If I'm wrong on this, I welcome corrections :D

[Robh3606]

Take a look in the 5234 manual. To change your cards over to the 4343 you would need to change R1-R5 on the cards. Very simple modofication if you don't like how it sounds with the generic 250Hz card.

http://www.jblproservice.com/pdf/Vintage%20JBL-UREI%20Electronics/JBL-5233_5234.pdf


When you switch the speakers to bi-amp, you bypass both a 52mf capacitor and a 2.9mh inductor on the HF side, and the 5.4mh inductor on the LF side. However, the bypassed components on the HF side, I think, function to attenuate the HF side, not as a HighPass crossover.

Why??

Rob:)

[4343b_bremen]

I will preface this with the disclaimer that I have not bi-amped my 4343's, so my input is purely theoretical. When you switch the speakers to bi-amp, you bypass both a 52mf capacitor and a 2.9mh inductor on the HF side, and the 5.4mh inductor on the LF side. However, the bypassed components on the HF side, I think, function to attenuate the HF side, not as a HighPass crossover. the HighPass crossover is not defeatable, so if you use a standard 250hz card in the crossover, you will have two HighPass crossovers in the circuit (one active, one passive) and one LowPass, in this case at slightly the wrong frequency, and your frequency response hole will be even larger than you thought. JBL's factory bi-amp solution was the 52-5140 crossover card (labeled 4343 LowPass), which did not have a HighPass section - it passed HighPass through to the outputs, though I don't know if it had any attenuation. I think it was 275hz LowPass only, 12db/octave. In your case, you could approximate this by splitting the fullrange output of your preamp and sending one leg through the crossover for the LowPass (woofer), the other straight to an amplifier with a gain control for the HighPass (MF/HF/UHF).

If I'm wrong on this, I welcome corrections :D

Hi..

.. perhaps I am wrong, but I understand the network 3143 this way.. ;) "If I'm wrong on this, I welcome corrections too :D"

51030

Section "4" (red) is the switched-off part (low-cut) of the Filter for MF, that works in addition on HF and UHF too, so the advantage to bypass this section will clear also HF and UHF.. ?

Section "3" (blue) is the high-cut filter for MFs neighbour 2420+horn+lens (HF)

Am I wrong?

So I understand the advantage of bi-amping the 4343b in bypassing section "4", that works on MF, HF and UHF ... -- and bypassing high-cut for LF .. or am I wrong? :)

Best regards..

Andreas

[4343b_bremen]

Take a look in the 5234 manual. To change your cards over to the 4343 you would need to change R1-R5 on the cards. Very simple modofication if you don't like how it sounds with the generic 250Hz card.

http://www.jblproservice.com/pdf/Vintage%20JBL-UREI%20Electronics/JBL-5233_5234.pdf



Why??

Rob:)

OHW.. :o))

Thank you, Rob.. -- just changing the values of some capacitors, and my 5234 will work at 300 Hz crossover, al 4343b likes best..

-A-

[HCSGuy]

OK, I took a look into it and learned something :)

I'm stealing this graph from an old post (thanks Giskard!), here's the post:
http://www.audioheritage.org/vbulletin/showthread.php?462-4344-4345-4355/page2

The graph shows the 4343/4350 card (JBL 52-5140) in yellow - Giskard puts it at about 255hz crossover. It looks pretty straightforward, 12db/octave, so you could swap out some components and make one.

I think 4343b_bremen is right in that the #4 is the HP filter for the MF and that it is out of the circuit when the switch is set to Biamp. It looks to be in the circuit for MF, HF, and UHF drivers, though it is out of band for HF and UHF.

My confusion stems from my having the stock JBL card for the 4343's (52-5140), and it is labelled "4343 Lo", which led me to assume it is low pass only, though it is loaded as JBL specifies for a 52-5140 card - anyone have any ideas what the "Lo" nomenclature is for?

Thanks!