View Full Version : Rebuilding 4343 monitors

04-30-2003, 02:47 PM
Hi! First I have to say that this is a really great forum!

At the moment I try to rebuild a pair of 4343 monitors.
Until now I have:
original cabinets in studio grey
original x-overs 3143
original 2420 mid drivers incl. Horn
original 2405 UHF drivers

What is missing:
2121 midrange transducer
2231A Bass transducer

Now the questions:
2121 are hard to get. I know that they can be replaced by 2121H, 2122H but they are hard to get too.
What can I do? Some other possibilities?

the 2231A is hard to get too. It can be replaced by 2235H. Is there big loss in sound? Is it possible to recone a 2225H to a 2235H?

Please give advise
Thanks in advance

Greetings from Germany, Guido

04-30-2003, 02:50 PM

I forgot to ask for the acoustic lens (2308?) How important is it?

04-30-2003, 04:19 PM
I know about a guy who built his own 4343's. He had the same problem as you getting his hands on a pair of 2121's. Instead he got a pair of LE10A's. He claimed that in the frequency-range the driver is working, its just as good as the 2121. One thing though: the 2121 is more efficient, but in the original 4343 there is a fix moderation in the network lowering the 2121's efficiency to about the same level as a LE14A.
He used 2235's and was very pleased with their perfomance.
Good luck!


Tom Loizeaux
04-30-2003, 07:28 PM
I just got a pair of 4343s a few weeks ago. One of the 2231As had been reconed with a 2235H cone/coil. The other 2231A's surround was rotted. I decided to recone the bad 2231A with a 22325H cone/coil to match the other one. I belive they will sound great in these cabinets made for the 2231A. The 2121s were also in need of surrounds, but the rest of them were in great condition, so I'm having them re-foamed.
I briefly listened to one of these cabinets before taking the drivers out for service, and they sounded wonderful! Very full- range with a lovely, smooth midrange that my other 3-way JBL studio monitors just don't quite have.
Now I have to touch up and re-paint the cabinets while I'm waitng for the drivers to come back. I am also considering changing the fabric on the grille frames, but that can wait. I still need to find a pair of JBL 4343 nameplates to make these like new.
Please keep us posted about your restoration.


04-30-2003, 08:41 PM
Hello Tom

Did you get the pair out of the Manhattan studio on Ebay about a month ago?? I was tempted as I had a nice refund from Uncle Sam but I just don't have room for them and my wife will have me commited. I really wanted to get my hands on the Urei 811C they had but same deal. Good luck with them!


Ian Mackenzie
05-01-2003, 02:03 AM
For the 2121 the current driver is a 2123, it should work okay, these have been on ebay recently.

The other option is the JBL tent sale for the 2123, but you will need a friend in the USA to handle the shipping.

PHL (France) made some very nice 10" mid paper cone drivers, these would be the next best choice, PassLabs used PHL in their new Rushmore Statement speaker (US$20K+)


Tom Loizeaux
05-01-2003, 05:44 AM
Yes, the 2308 lenses are important. They distribute the output from the 2420 drivers. You wouldn't like the dispersion without them. Jamin' Jersey usually has a few of these for sale.


05-01-2003, 06:51 AM
You can use an LE10A, K110, LE10H, LE10H-1, LE111H, 2120, 2121, 2121H, or 2122H to build a 2121.

You cannot use an LE111A, 2123H or E110 basket. They're different.

And yes, the 4343 is still high end after 20+ years. I personally find it to be a significant improvement over the L300/4333.

05-09-2003, 12:35 PM
Thank you guys!

I will keep you informed how it goes.
At the moment the cabinets are repainted.

But I'm still looking for
Bass trancducers
Midrange transducers
and the lenses.

If you can help......

Ian Mackenzie
05-09-2003, 02:29 PM

I refer to Giskard post about about the 2121, and in Monte's thread about parts, the 2235 can be derived from te basket of a number of 15 inch baskets, just get a re coner to fit the 2235 re cone, (do a search for Giskard post)


Tom Loizeaux
05-13-2003, 06:43 PM
All this talk recently about 4343s is getting me excited! While I'm still waiting for my re-cone/re-foams on my 2231 and 2121s, I'm finishing up my cabinet restoration, replacing some dirty fiberglass and cleaning up my crossovers. I've decided to follow RobertG's advice and install bypass caps in those stock 3143 crossovers. I plan to run these in the bi-amp mode but feel I will improve the transients by adding bypass caps.
When I get these up and running I'll post a review of these 4343s compared to my 4312As, 4320s and 4333Bs.