4340 & 4341 references thread

This thread is an index to various other threads and references on the early JBL 4-way monitors.
The 4340 was design to be biAmped.
The 4341 had a conventional crossover.
These monitors were built for roughly 2 years (1973-75) and were followed (1976) by the larger and now better known 4343 and later the 4345 monitor (18" woofers).

(Below photo credits: upper 2 pix courtesy of Anthony L100 and lower 2 pix courtesy of Riessen)


This is designed to be a longer term references to other resources here and outside on the web.

I'm trying very hard to keep the thread "on topic" so please give me the next few days before posting ANY replies or comments here.
Your PMs are most welcome.

In a previous thread, Giskard posted this information -

The 4340 is the bi-amp only predecessor to the 4343.
The 4341 is the passive only predecessor to the 4343.

The oldest Pro price list I have only goes back to April of 1977 -
http://audioheritage.csdco.com/vbull...tor+price+list

Thanks, Giskard!
Here is a Link to 1974 4340/4341 brochure in Library section of this website

The drivers specified for the model 4340 & 4341 are listed in the graphic excerpt posted below (chart posted courtesy of JBL)
Note that the Model 4343 (see brochure) which replaced the 4340/41 used the same drivers and a somewhat larger cabinet.


3140 - crossover used in 4340 (biamp config)
3141 - crossover used in 4341

3143 - crossover used in 4343
3145 - crossover used in 4345 (final version of the 4 way crossover used in this series)

Here's a picture of the 3141 crossover in a 4341 - its bolted the bottom just behind the woofer and is normally covered with soundproofing material
The grey cable runs up to the L-pad assembly, and the paired lines go to the individual drivers and the rear terminal panel.

Below this is page 3 from the JBL Professional Studio Monitor reference chart listing the components of various monitors.

Examples of some immaculate restoration

Anthony L100 has a very clean original set in the UK - http://audioheritage.org/vbulletin/s...highlight=4341(images midthread)

Riessen's 1st 4341 system - 8/05 - 01/06 - 4341 Back to Life (white cones and all!)

Riessen's 4341s - more pix (Feb 2006) - http://audioheritage.org/vbulletin/s...highlight=4341

Some recent sales of 4341 monitors

LHS Forum Ad - May 07 - Long Branch, NJ - s/n 10083 and 10105
surrounds gone on 15"s and 10", 1 grill damaged, scratches

Ebay #290105113709 - May 07 - Columbia, PA - (no bids) s/n 10009 and no s/n
wrong 15s and 10s (2234s and 2123s), bad lPad on 2405. no grilles, cabinets very very good.

Ebay #250089231148 - Mar 07 - Philadelphia, PA - sold for $2400
All correct drivers - appear good, have grills, bad surrounds on 15s

LHS Forum Ad - Jan 07 - Detroit, MI
Look to be very clean and complete, and had the rare white coned 15" woofer.

Ebay #320047984198 - Nov 06 - Tucson, AZ - sold for $1500.
The pictures are now gone. The original ad read:
"This pair of Monitors are huge and must be picked up or trucking arranged by buyer. They are sold as is, but I will describe them honestly.The speakers need to be re-coned. The higher frequency components are perfect. Even in this condition they sound Incredible. The cabinets are rough in the back but fair in front. Some chips in the wood I posted a lot of photos if you need more ask.Don't forget the Buy It Now option disappears after the first bid !!!Just the JBL 2405 Ultra HF Slot Tweeters are worth $400.00 These are extremely rare and have been considered among the finest Monitors ever built. Drivers with pure silver impedance controlling rings etc. etc. A very rare opportunity."


Ebay #9721369094 - May 06 - Emigrant Gap, CA, s/n 11521 & 11557
Sold for $1750 - pictures now gone. The original ad read:
"a good working pair of studio monitors ,They contain the following components 2405 slot tweeter ,2420 driver with horns and lens,2121 10 inch mid-range speaker lans-a-loy surrounds need replacing soon hard but not cracked. ,2225h woofer .SERIAL NUMBERS ARE 11521 AND 11557.Cabinets could use some restoration ,no major damage, plant spot on one top ring but not raised very repairable .Shipping weight is 390 pounds each speakers 175 pounds each .Grills are missing .Grill can be bought at the speakers works in tulsa ok. Dave makes great grills.WILL SHIP OVERSEAS FOR $500.00 INCLUDES GREAT PACKING JOB AND DELIVERY TO PORT . I USE SHIPPING INTERNATIONAL AND NNR They sound better than any altec lansing ,all they need is grills and 2231a's to be correct ! New foam on the 10 inches and they are killer control monitors ,great for mixing ...TRUE SOUND REPRODUCTION!"

March 2007 - ebay 4341 sale: Philly

April 2007 - ebay 4341 sale: York, PA

After watching the previous pair sell in Philly, I was amazed to see another pair pop up near York PA just a few weeks later. In the ad, the seller said the original woofers had been changed out for a pair of 2234s, and the 2121 10" Midbass drivers had been changed out for a pair of 2123s. Something was wrong with the crossovers (or lPads of 2405s - buyer beware), one of the foilcals was gone, there were no grills or lenses, and it was stated that they had scratches etc.
But with all the listed flaws the starting price was $2000, which seemed high to me.
I wrote the seller and got some more blurry pictures via email - he was very busy and didn't really have time to sell them properly. I offered a buy it now price a few hundred less than his offer - but he decided to let the auction run its course.
No one bid.
After that, I wrote again with my offer and was persistent for two weeks, we managed to finally agree on a price and a week later I was bringing them home.
When I oiled them up I found the cabinets are in VERY fine condition. I have a spare set of lenses from an earlier project, and a few spare 2420 7 2405 drivers just in case I need them.

But even now they sound great and I feel VERY lucky and am grateful to have them ...
For me, the journey has just begun.

Dimensions and Cabinet Volume of the Professional Studio Monitors

Ian wrote and reminded me of one of the significant changes as the 4-way Pro monitors evolved.

In post number 2, the JBL Pro Studio Monitor chart shows the various drivers used in the 4 way studio Monitor series. Giskard has said that the 4340/4341 and 4343 have basically the same components, yet notice in the chart in this post that the 4343 has a significantly larger cabinet than the earlier 4340/41 series.

The 434x JBL 4 way Monitors consist of two chambers within the larger enclosure. The lower area is a large ported chamber for the 15" woofer, and the 10" woofer has its own smaller, non-ported chamber to work against.

When I first opened my 4341, I removed the 15" woofer so I could access that lower chamber to replace the rear terminal panel (which had been modified by the last owner) with one using 5-way connectors. Once the woofer was out of the way I was surprised to see it was packed with sound insulation. My exact words were "rammed full of soundproofing insulation". I asked a few long-time members if it was normal for the cabinet to be so full. Riessen assured me that it was normal for that model.

All I can figure is that due to the relatively smaller volume of the cabinet, it was packed tighter than other models to compensate for the reduced volume of the main woofer cavity. Remember, the low frequency drivers need room to move, room to work.

The dimensional data presented below came from the sales brochure in the Library section of this site - the 4345 model lacked such info - its brochure only provided the volume in cubic feet for the upper and lower chamber model - I found the other dimensions in the Technical Reference of the Forum: System Information - look below the "Designer Note by Greg Timbers."

Worthwhile improvements to the 4340/4341 Monitors

Considering that the 4340/41 and the 4343 are basically the same components, recommended updates for the 4343 ought to apply to the 4340/41

To save Giskard from posting these tips yet again, I'll quote his post from The JBL 4345 Club thread.

Quote:

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Originally Posted by Giskard

One last time:

Stock 4343
1. Bi-amp and build a biased bi-amp only 3143 filter
2. Aquaplas the 2420 diaphragm

Upgrade to 4344
1. 2231 => C8R2235
2. 2121 => C8R2122
3. 2420 => aquaplased D16R2421 or D16R2425 diaphragm
4. Bi-amp and build a biased bi-amp only 3144/3145 filter

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In a discussion with Oznob, Mr. Widget commented:

Quote:

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Originally Posted by Mr. Widget

...with the 4341s... I'd also update them to 4344s, but do so in a manner that was reversible for the collector market.

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For a really detailed version of the phrase "Convert the 4343s to 4344s" please read Porschepm's post detailing the 2 1/2 year upgrade of his 4343s - see #228 at http://www.audioheritage.org/vbullet...&postcount=228
Highly recommended!

Notes and links on the Crossover Network


I highly recommend reading the "Designer Note by Greg Timbers" (re: the 4345 Monitors) in the Technical Reference of the Forum: System Information. Note his recommendation to go to a Charge Coupled network. Which was't used when the 4340/41s were designed, but made a major improvement in later JBL systems.Please also read the "4343 to 4344 upgrade" thread mentioned in the post below ...

Also read 4343 Crossover thread here - (its worthwhile, but does go 31 pages!) http://audioheritage.org/vbulletin/s...skard+networks

This is designed to be a longer term references to other resources here and outside on the web. We are trying to keep the signal to noise ratio high.

To keep the thread "on topic", please give me the next few days before posting ANY replies or comments here.

Your on-topic images, information, insights and links are most welcome and I'll give you credit for your contributions.

Your PMs are most welcome.

Thanks for your help!

Heather James
__________________

Just bought a pair of 4340
On the back I can see it`s for bi-amp connection. But I also got an elektronic cross-over 5232. Is this also supose to be connected ? if so, do anybody know how ?
Best regards
Svend Hansen
DENMARK

Quote:

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Originally Posted by svendmich

Just bought a pair of 4340
On the back I can see it`s for bi-amp connection. But I also got an elektronic cross-over 5232. Is this also supose to be connected ? if so, do anybody know how ?
Best regards
Svend Hansen
DENMARK

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Lots of discussion on biAmping and such in one of my threads.
The main point is you take the output of your preamp, run it into an Electronic Crossover to create a high split and a low split.
The Split point is 290Hz ...
Low side goes to an amp that basically just feeds the woofer. Use reverse polarity for the woofer feed.
High side goes to another amp that feeds the passive in the speaker that feeds mid-bass, horn and slot tweeter.

That's the quick basics.

If you are interested - I did a whole long thread as I developed my pair of 4341s over a 5 year period.

Original purchase, biamping, trying various amps and electronic crossovers ....

http://www.audioheritage.org/vbullet...onitors/page11

First, thanks to hjames for gathering all the data on 4340 4341.

Quote:

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Originally Posted by Odd

First, thanks to hjames for gathering all the data on 4340 4341.

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Well, go to JBL Pro for a clean manual!

http://www.jblproservice.com/pdf/Vintage JBL-UREI Electronics/JBL-5231_5232.pdf

UGH - its a very ugly scan! I thought we had better ones here, once ...

Can we reference some grille frame dimensions for the 4341? I need dimensions and hopefully someone has some pictures of grilles that show their construction. Also blue grille cloth for walnut cabs and black cloth for gray, right?

hi every one
I have paire of altec 9849. and I want completely rebuild the crossover. where should I contact. or which frum should discuss.
thank for answering

Quote:

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Originally Posted by koshan

hi every one
I have paire of altec 9849. and I want completely rebuild the crossover. where should I contact. or which frum should discuss.
thank for answering

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Not this one -
you are COMPLETELY off topic in a JBL Studio Monitor thread ...
Look a little more ...