4340/41

[Ian Mackenzie]

The 4343 gets a lot of air play but we don't hear much about the 4340/4 on the forums so I went looking on the JBL web page and found this data.

http://www.jblproservice.com/pdf/Systems%20Reference%20Charts/Studio%20Monitor%20Series.pdf

Aside from being a biamp only (4340) or full passive version (4341) the 2231A ands 2121 is the main difference in the 4340/41 (as did the 4343) while 4343B used the 2231H and 2121H

The top panel is also non removable in the 4340/41 and the enclosure is slightly shorter at 37 3/4, and deeper 19 3/4 and less wide 23 1/2 than the 4343 at 41 5/8 high, 25 wide and 17 1/8 deep. The dog box of the 4340/31 is 0.3 cu ft3 and the 4343 0.50 cu ft3.

What I did find interesting was the crossover schematics.

I am curious as to what driver polarity orientation was intended for the 4341?

The location of the 1.5 uf capacitor shunted after the 4 uf capacitor in the Hf bandpass filter is interesting rather than after the 0.25 Mh choke ? It must have been an interesting load for amplifers before they added the 4 ohm resister.

http://www.jblproservice.com/pdf/Network%20Schematics/3140%20Network.pdf

http://www.jblproservice.com/pdf/Network%20Schematics/3141%20Network.pdf

If anyone owns either of these versions some pics and discussion would be most welcome.

Ian

[norealtalent]

partial
...The location of the 1.5 uf capacitor shunted after the 4 uf capacitor in the Hf bandpass filter is interesting rather than after the 0.25 Mh choke ? It must have been an interesting load for amplifers before they added the 4 ohm resister.


http://www.jblproservice.com/pdf/Network%20Schematics/3140%20Network.pdf

http://www.jblproservice.com/pdf/Network%20Schematics/3141%20Network.pdf

If anyone owns either of these versions some pics and discussion would be most welcome.

Ian


I would love a little detail rargarding your cap/coil before after comment. It seems that is exactly the kind of scenario I am finding with the westlake x's. I sent you a pm. ANY thoughts would be GREATLY appreciated. Many thanks, Dave:bouncy:

[Anthony L100]

The 4343 gets a lot of air play but we don't hear much about the 4340/4 on the forums so I went looking on the JBL web page and found this data.

If anyone owns either of these versions some pics and discussion would be most welcome.


Hello Ian, I have a pair of beautiful 4341s and I was beginning to think they were the only pair ever produced until I noticed a thread by Riessen who has a pair in restoration. Were they not a big seller in the States for some reason? I searched here and results are few. This pair came from Germany just about a year ago, advertised as near mint but requiring new foam on the 2231As. I negotiated to have the seller get the surrounds done in Germany to which he agreed, not really being aware of the "easy route" on the front of cones job, so I was a little dissapointed. All units seemed to be OK though.
The Grilles had never been used and were wrapped up and thats how they remain as we have a very destructive cat!
After the 800 mile round trip to collect them, (that's another story) and hooking them up all appeared almost fine. The L pads were "scratchy" and the lans-a-loy on the 2121s was very rigid. It was then that I discovered what a wonderful place this is!! I posted about the lans-a-loy and Widget quickly had me understand they weren't supposed to be that rigid! Never one to shy away from a mechanical problem, I read up all about re-surrounding and thought I could do the job. Not being entirely happy with the foam on the front of the 2231s I decided to do those as well. Rick Cobb supplied the goods which turned up in about 8 days! I had an old 122A with an open voicecoil to practice on so I had a go at that with great results. As it was in need of a complete cone I took it to bits! I carefully inserted a surgical scalpel between the spider and basket and removed it with no damage at all. The voice coil looked perfect apart from where it was broken due to rubbing right where it goes over the top of the former and back down to the lead out wires (hope i'm explaining this OK). With nothing to lose, I unwound one turn from the coil, which gave me enough wire to reach the lead out eylets on the cone. I soldered it in place, painted over the repaired areas very lightly with epoxy resin, measured the DCR and hey-presto!! I used the same scalpel to remove the dust cap, borrowed a shim from a cone kit I had lying around, shimmed it up, glued the spider, left overnight, re-surrounded the next day using 30Hz test tone, left overnight. If it hadn't worked I wouldn't have been upset, but... Listening test, as they say on e-bay "no rubs or scrapes" I was stoked! That driver is still used regularly in an L100/L65 clone which gets plenty of abuse and still sounds sweet.
Sorry to digress. So the 2231s were next for the treatment, the biggest problem was the removal of the new foam from the fronts. I managed it without peeling a layer from the cone, it is tricky and I wouldn't recommend it but I felt happier having done it. Again, everything went well and they sound just fine. The 2121s were left till last as I felt that I would benefit from more experience to deal with these, mainly due to the fact that the area to attach the foam to the basket is a lot smaller. However all worked out OK with no rubbing etc. The final task was to remove the L pads to sort out the dirty tracks, this was a lot simpler than anticipated. The foilcals were removed as reccommended and undamaged, screws removed and then the mother of juggling exercises to get the board with the pads out. I don't think they considered us when they designed these babies! WHOA! these L pads are much bigger than any I have messed with before, I guess they have to deal with a lot more current than L100s etc. These pads are very easy to work on (I am sorry I did not take photos) and are designed to be stripped down. I don't know how good the ones you guys get from Parts express are but having cleaned the tracks and wipers and greased the spindles, they now work as new! And they're original.
This just about completes the work to date and the difference is very noticable to me, particularly the 2121 which is now allowed to function correctly. I was very fortunate to be able to take these to a friends house which has a huge (for the UKhttp://audioheritage.org/vbulletin/images/smilies/wink.gif ) room where they can really breathe and they sound spectacular, there is just something about compression drivers that I love, the girlfriend boxes me about the ears toohttp://audioheritage.org/vbulletin/images/smilies/biggrin.gif. I'm gonna try and attach a couple of photos now but if i'm unsuccessful I will do it later. Thanks to all who have offered advice, I hope you can see it has been put to good use, and thanks Ian for starting this thread, I would love to hear more about this underrated JBL!
If you ever see me offering a 122A on ebay, BEWARE!!!!!!!!!
I've included a photo so you can spot it:blink:

[norealtalent]

Thank you for sharing. The speakers are very nice but Oscar is gorgeous.:bouncy:

[saeman]

It's nice to see another pair of 4341's out there. Thanx Ian for getting the ball rolling on this awesome and very rare monitor. I think it's worthy of some investigation. As stated, the 4343 get's all of the press and seems to be a JBL benchmark, yet the 4340/4341 started it all. The 4340 and 4350 were JBL's first Pro Monitors as we know them today, with the beveled face trim and protruding blue grilles. There are many 4320's around but they just don't have the image shared by the afore mentioned design. The 4340/4341 came out in mid to late 74 along with the 4350. It was offered thru 1975 and then replaced with the 4343 in 1976. I have seen only a very few pairs of 4341's and I've never seen a pair of the bi-amped 4340's. Both variations are certainly RARE.

I waited and searched for years before I found a pair. They were dogs but worthy of the effort required to bring them back to life. I resored one cabinet and am now at a stand still. The walnut veneer I used, now installed and oiled, is of poor quality and I'm sick about the appearance. I recently purchased some very high quality AA premium walnut veneer and will strip this one bare and do it again. I'd never be happy leaving this pair less than perfect.

As Ian stated, the components are the same as used in the 4343 - 2231A, 2121, 2420 and 2405, that is - during the 1975 production period. There are some subtle differences in the x-overs although they are very much the same. When the 4340/4341 was first offered, the 2231A woofer did not exist, nor did the 4-bolt square mounting flange for the 2405. Up until 1975 production of this monitor, the 4340/4341 was offered with the 2230A (white aquaplas coated cone) and the 2405 with the split ring front baffle mount. As a JBL nut/historian/collector, this is the pair I am untimately looking for.

Giskard - you may know - When did the 2231A become available? It is my understanding that it was early to mid 1975.

Ian - I currently have one cabinet empty and parts in boxes. If I can help you answer any questions about the x-over just let me know. The output wire color coding to the individual components is the old variation instead of - green LF, white MF, yellow HF and orange UHV like the newer monitor's crossovers are coded.

As already noted, this monitor's cabinet is smaller than the 4343 and consequently packed full. There is a removable panel on the cabinet rear at the top to access the 2420 and 2405. Like the 4350, the base is removable and there are four eye-bolts installed for hanging the monitor.

I don't understand the issue with having cats around JBL monitors. I have 3 abysinians and the first time they tried to climb the grills of my 4350's I simply told my wife that either their front claws go or they go. Two weeks later they weren't climbing grilles any more. I love them and they cost more than a good pair of monitors but ??? !!! ??? We must keep our priorities straight.

Rick
http://audioheritage.org/vbulletin/images/smilies/smile.gif http://audioheritage.org/vbulletin/images/smilies/bouncy.gif http://audioheritage.org/vbulletin/images/smilies/wink.gif

[Ian Mackenzie]

Wow nice monitors and nice pussy cats. Is it possible to psot a picture of the crossover.

I like the white cones....that was the first thing I remember about JBLs in the 70's

I plan to visit Otis tomorrow night....I will post a picture.

Ian

Ps I have ordered all the parts for the 4340 crossover using Claritycaps and plan to make a replica for my brothers wives (my first 4 way JBL effort c 1980). I will post details in due course.

[Anthony L100]

Ian, as Rick has one cab stripped, hopefully he will be able to give you all the
x over info and pics you need. If not, I am happy to help. Let me know exactly what views you need. I don't have the in depth electronic knowledge to comment on the location of the 1.5uf cap in the highpass filter, but I would be interested to hear what the experts think.

I will take some proper photos soon, without the wire grilles and post them.

BTW does anyone know if the thick foam strips which sit over the edge of the surround on the 2231s are available seperately as mine are a bit flaky and I didn't want to re fit them.

Rick, I hope your new veneer does the trick! The cats booked in to have his feet removed tomorrowhttp://audioheritage.org/vbulletin/images/smilies/cryingsmiley.gif

[Ian Mackenzie]

Thanks all for the input.....those white cones have a certain attraction according to the woman folk......:rockon1: :banana: :thmbsup:

[saeman]

Hello Ian: I'll take some pics of the x-over this evening and post them. You can then let me know if you need additional shots. Here's some pics of 4341's that I have kept on file. The gray pair I believe belong to one of our forum members. Can't remember his name but he has several other studio gray monitors. Maybe he'll see this thread and tune in. Rick

[saeman]

Here's a few pics of the first cabinet I restored. You can see the condition they were in. HOW can a pair of monitors degrade to such a state of ugliness??

[4313B]

HOW can a pair of monitors degrade to such a state of ugliness??People just don't care dude... :dont-know

[saeman]

People just don't care dude... :dont-know

I suppose you're right. At my carwash I see cars come in that don't have any paint left on them - never waxed and seldom washed unless it rains and we're talking expensive cars. I on the other hand must be real anal as I have always taken good care of everything I own. I bought my Sovereigns in 1974 and have dragged them from Hawaii to Maine to Charleston to Illinois to Phoenix to Topeka and back to Illinois. I raised 4 boys in the process and have always had animals in the house. Today I could easily rate them 9 out of 10.

[Ian Mackenzie]

Juicy!:applaud:

Ian

[Alex Lancaster]

:applaud: Ian: Magic!

[Ian Mackenzie]

The first set of JBL 4 ways I saw and heard were those above with Lans..surrounds on the 2121.

Seems like only yesterday....nearly 30 yrs on.

I think we need to put these images somewhere special, in a 4340/41 showcase in the Library perhaps, it is real rare 70's 43XX Lansing Heritage.

Perhaps Don can avail.....

Ian

[Mr. Widget]

Perhaps Don can avail.....Don who?


Widget

[Chas]

Don who?


Widget

I think he's buried in a snow drift somewhere in the wilds of Winterpeg, Manitoba...:p

[norealtalent]

Don who?


Widget

No Widget, not :screwy: Don Quixote.

[jbl4ever]

Some pictures of the crossoverhttp://audioheritage.org/vbulletin/images/smilies/smile.gif
http://dmbshare.org/pictures/co001.jpg
http://dmbshare.org/pictures/co002.jpg
http://dmbshare.org/pictures/co003.jpg
http://dmbshare.org/pictures/co004.jpg

[saeman]

Ian: Here's a few pics of one of the 3141 x-overs. It looks pretty bare compared to some of the other 31xx series. Note the serial number. One of the first few made. If you need other pics let me know.

Rick http://audioheritage.org/vbulletin/images/smilies/bouncy.gif

[Ian Mackenzie]

Okay,

I have started a revival of the 4341 crossover and done some voltage drives and amplitude response plots of the actual drivers.

I see this as an intuitive and exploratory investigation of why and how JBL did what they did all those years ago.

The curves are ; the 4341 2505 voltage drive, the 4141 2405 amplitude response and the 4345 voltage drive, the 4145 2405 amplitude response.

As you can see they are very different and tomorrow .I will post the horn curves and then the overall response curves.

Ian

[Ian Mackenzie]

Posted below are the voltage drives and ampitude response graphs for the 3145 equivalent and 4141 crossover types, last is a overall mid field reponse, the midrange aspect of the curve should be ignored due to microphone position.

Note these amplitude response and voltage drives where doen with a 2420 fitted with a DR82425 diaphragm. Some variation can be expected if one where to use the 2420 with the DR162420 "original diaphragms.

There are a few things to be aware of. The horn bandpass filtyer is sentivite to impedance fluctuations and this is one reason why they employed a constant impedance attentuation pad. Also, it would seem the 0.16 mh choke as siginificant dcr in order to operated as specificied.

Maybe Giskard can comment on the 0.16 mh choke dcr.

Time for a night cap!


Ian

[Anthony L100]

As promised, some more / better pics. These 4341s are about as original as they come having only had new surrounds on the 2231As and 2121s. The cabs are beautiful and I am very proud of these and will probably keep them forever. Sonically, they could probably be improved by re-coning the 2231s with 2235 kits and possibly replacing the diaphrams in the 2420s but they sound wonderful as is, so what's the point?

[Anthony L100]

More pics, I hope these are appreciated as I realise they use some "space":D

[Robh3606]

Sure they are!! It's a pleasure to see a pair in such nice shape!

Rob:)

[Anthony L100]

Only a few more!

[Anthony L100]

The last few.

[4313B]

Very nice! :yes:

[bldozier]

Dope.