JBL 4343 rebuild and configuration project

[Rolf]

Since you are bi-amping your 4343s, you could turn the L-pad pots all the way up and not waste power from your high frequency amp. Set the 2121 to max, the 2420 to +3, and the 2405 to max. Then you could turn down either your crossover levels or turn down you power amp feeding the high frequency section to get the balance you want without burning off power with your L-pads.

Tom

An interesting idea! Questions: I have been measuring the "-1 -2 -1" according to Ian's advice, and the result is excellent. Will your suggestion of" max -3 max" do the same? (Guess I can just try, but ...) I have never seen my hi frq amp have any trouble (2x200W 8 Ohm). Same power to the woofers, and on some records with very low notes I have stop turning the volume up.

[Guido]

OK, lets see.

The notes on the right side in the pic below indicate that this 5234 has been upgraded with some features of the later 5234A and 5235:

1/4 jacks and bypass caps added
C1, C2, C3, C5
C101, C102, C103, C105
0.1uF
5-16-04

This means only that the bypass caps that where an improvement from 5234 to 5235 are also added here. NICE.

- caps type used
- are the cards 12db or 18db

The cards are 12db types and the right ones for 4343. If you tell the values I can check if the cards are 4343 or not. Original 4343 cards are stamped 52-5140. If yours are different we can modifiy them.

[Fangio]

Hi Guido, thanks for the offer. Here are two pics of the cards, hope this helps.

Sorry for the late answer, hope also there isn't a huge call for action.

[Guido]

Those are 4343 cards

[Ian Mackenzie]

Fangio, FYI:

http://www.audioheritage.org/vbullet...&postcount=194

[Fangio]

I hear ya, Ian. Thanks for putting me on the list.

[Fangio]

Ok, this was a year ago – time for an update.

At weekend there will be a tryout session for some different, larger midrange horn combinations, and to utilize these drivers.

Also finally got a pair of undamaged 2308's from another member – thanks.

[richluvsound]

Hi Fangio,

have you thought about putting dusted 2425 dia in them .

Ian swears by it . Guido has dia and I will dust them for you if you like.

Just let me know if I can help in anyway.

Rich

[Fangio]

Rich, thanks very much for the offer, you know that I'm open for options.

I'm cautious trying to accomplish improvements in the right order, and should probably have an adequate basis inside first, for such driver finetunings.

[Fangio]

Thought I could add more updates here, and some more recent pics with the original cones that I'm currently using – 2231, 2121 – before I'll modify the boxes again. Those do pop up over here every now and then, it's just a matter of patience.

Closer to stock configuration these 4343's won't come. But since I've got some 077's recently I will try these in place of the 2405's for a while. I expect them to be a tad louder with the 3143 networks.

The little black box is a passive filter I'm using for the woofs since a year – definitive superior in bi-amp mode for balancing the system, over the good old 5234. The active filter also absorbed quite a bit of the warmth and accuracy that tubes had added to the chain.

Obviously 2008 might become the year of the grey cabs.. a second driver set is almost complete.

[richluvsound]

Fangio,

I have never heard 4343. I'm really looking forward to it

Rich

[Carl]

My two 4343 WX 's have been producing extrordinary sound since the mid 70's when I bought them new, direct from JBL.

In the 90's I had the 15 inch drivers re-built because the foam surrounds had given up. Now the ten inch drivers have the same problem, but unless they are glued in, I can't remove them (After removing the four mounting screws.) and there doesn't seem to be a gap between the frame and the baffle-board so I could pry them out.

Any thoughts?

[Eaulive]

My two 4343 WX 's have been producing extrordinary sound since the mid 70's when I bought them new, direct from JBL.

In the 90's I had the 15 inch drivers re-built because the foam surrounds had given up. Now the ten inch drivers have the same problem, but unless they are glued in, I can't remove them (After removing the four mounting screws.) and there doesn't seem to be a gap between the frame and the baffle-board so I could pry them out.

Any thoughts?

Remove the baffle or the 3335 and push it out from behind.

[BMWCCA]

Remove the baffle or the 3335 and push it out from behind.

Isn't the mid-bass section a sealed sub-chamber?

[Robh3606]

Isn't the mid-bass section a sealed sub-chamber

Yes so it won't work trying to push them out. Just carefully try getting a putty knife under an edge to get them started. Sometimes the frames stick to the baffle. The only other thing holding them could be the ring gasket.

Rob