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View Full Version : So, 4340/4341 cabinets or just what are they? Curiouser and Curiouser



mech986
03-28-2008, 01:05 AM
Sorry for a bit of cross posting but I thought more general questions need to be asked about these cabinets and more help can be solicited so I'm posting in this area.

I brought these boxes back home from this thread:
http://www.audioheritage.org/vbulletin/showthread.php?t=20502

Seller told me he found them at an auctiion house with most drivers removed except the surround less woofers along with additional hi-end stereo gear (the Accuphase pre/tuner above and a Nak Dragon). He got all of it for a VERY good price. He didn't remember any details about the woofers or crossover, just that all the mid/horn/tweeters were already gone. He sold the woofers and crossovers to a friend of his - I"m trying to track that down to see what was there.

Comparing them with the 4340/4341 brochure here:
http://www.jblpro.com/pub/obsolete/4340_4341.pdf

I've loaded a few pics below - the condition is very good with only a few minor scratches and a small gouge on one top, plus the obligatory fade/water stain on the other top. Double 4 inch ports are in the right places, woofer opening is 14 inches with 4 clamp marks for a 15 inch woofer, and the upper horn opening fits a 2307 horn and bolt circle just fine. Looks like the 2308 lens attachment was an early screw on type that had the wood strip support typically found on the C50 Olympus instead of the later velcro plastic unit?

However, things are not all they seem to be - right size and general shape for the 4340/4341 cabinet, walnut finish - but no JBL Blue at all to be found, the midrange opening is only 7" wide probably housing an 8" driver instead of a 10" (haven't measured the inner doghouse for volume yet) and the two openings for the tweeters fit the 2402/2405 horn but are lower than the alignment with the upper midhorn that I've seen.

Also interesting although not easily seen in the photos I've attached is the tweeters used were clamped with the typical outer horseshoe used for 075/2402 bullets. Also, sharp eyed folks will note there is no vertical line for the 4340/4341 3 level controls of the crossover - there are only two holes above one tweeter position - and a set of 4 holes below that would indicate the crossover may have been bolted in on the baffle instead of on the floor as most Studio Monitor series were. No usual cutout for input terminals, just 4 push connectors on the back panel - bottom pair looks like they ran directly to the woofer, top wires were cut off, presumably for the crossover. Maybe used with an active biamp setup? Top back panels look like they were exchanged.

Also, although I don't know the inner construction of the 4340/4341 type cabinets, these don't have really robust inner bracing - most of it is like 1 to 1.5 inch square, no 2 x 2 or 2 x 4 bracing yet found. The top of one was stuffed full of fiberglass, the other seemed to be missing it (maybe taken out when the drivers were taken out. The lack of a 3 control crossover seems weird.

So its quite curious about what these may be - DIY or prototype, custom monitor, early version of the 4340 - maybe a sort of 4333-4ish 4 way evolution? (remember seller can't recall type number labels or any details of the mid drivers - were gone already). And I have no idea what mid cone driver they would have used since only the 4315 uses a 2108 8 inch mid.

I also checked and its not one of the EN5 or EN8 enclosures either - wrong dimensions and baffle layouts.

I'm starting a new thread about these to get more LH people to comment on these? Maybe ask Greg T. or Mark G. about what they might be? And then what to make out of them? Use an 8 inch mid driver or enlarge the hole and doghouse to suit a 10 incher? Let me know what you think.

Regards,

Bart

mech986
03-28-2008, 05:59 AM
Quote:
Originally Posted by mech986
Quote:
Originally Posted by jbl4ever
Hi Mech, looked at your speakers they are different
for sure. I think its a good DIY version. It was set
up to be biamped by the looks. The screw by the midbass appear to be the mounting for the doghouse?
It you leave them this way try a 2118h 8" driver.
If you are not going to build Xovers look for a pair of
3120A 1200Hz crossovers. Make some 3106-8K xovers
Dave:)

Hi Dave,

Thanks for the PM, would be great to have your comments in the new thread here:
http://www.audioheritage.org/vbullet...ad.php?t=20541 (http://www.audioheritage.org/vbulletin/showthread.php?t=20541)

Funny, I just picked up a pair of 3106 crossovers and could make the 3120A's. I've got 2 sets of 2118J's (16 ohm) from a pair of 4612's but no 2118H's (8 ohm) yet.

If I was going to do it, I'd probably run the bottom end through a Dahlquist active crossover and then figure out the 3 way from there.

Thanks for your thoughts. Do you mind if I post this to my new thread?

Regards,

Bart


Hi Bart no problem, early versions of the 3120 were 12 to 16 ohms not the A version which are 8 ohms. You will probably need a Lpad too. Wish you lived closer as I could let you try some crossovers. Maybe Zilch can help you. Dave:D

P.S
bart, dont forget to get some dowel rod to plug the Lpad holes, and to make a block off for the other tweeter hole.

just remembered Gold Sound use to sell a kit using most of them components but
had the 2404 tweeter instead. You might be able to get a pair of their xovers. I think the kit # was 15.
Dave

Thanks Dave for your insight and suggestions.

Regards,

Bart

subwoof
03-28-2008, 10:10 AM
In my stash of stuff I have 2 complete crossover / wiring assemblys with foilcals from a pair of 4315's that were destroyed. If you reconed a pair of 2118's ( I have a pair ) into 108H they would work for the 8" LM. The 2405 is the same and the 2203A woofer is REALLY close to the 2231 so minimal crossover tweaking in those ranges would be needed.

The cone mid to horn lens part of the network WILL need revision but at least the framework is there.

It looks like those were either prototypes or someone from the factory's assembly area whipped up a pair for their own use from stock parts. Note the alternate tweeter location is in the same place as the panel that supports the level controls ( kill 2 birds with one panel ). Also that "standard" panel's holes are also around the lens openings - one more clue to it's *prototype* usage.

This picture is from a dealer release package circa april 1974 showing the "to be announced" new monitors from JBL. Since we know that the earlier 4341's had the 2230 white woofers and a single port, it stands to reason that multiple variations were made and experimented with at that time.

If the room is there, enlarge the LM to 9 inches and make a new doghouse.

sub

mech986
03-29-2008, 11:00 AM
Thanks for the info so far guys.

A couple of questions:

1. what would be the usual doghouse volume for an 8 inch driver assuming one could be found like the 2118H/J, 2108, or 108H?

2. What would be the optimal size for the 10 inch driver, wasn't it around 1/2 cu. ft?

3. I'm thinking about rebracing the cabinet but concerned about reducing the cabinet volume any more than necessary - the 2235's I'm considering like the 5-5.5 cu.ft. range.

4. I'm also considering lining the walls with Dynamat like material to dampen the walls - interestingly, despite being pretty thick stuff, the walls are not as dead as I would expect - maybe DIY too thin or the material was not dense enough (early particle board). The BBC used the damped thin wall construction with birch plywood.

5. How much stuffing was up in the top section of the 4341/4343 type cabinets as mentioned before? Still the standard 1 or 2 inch heavy density fiberglass in flattened state stapled to the wall?

Regards,

Bart

mech986
03-31-2008, 11:28 AM
Well, got to measuring the doghouse, its 8 in x 8 inch deep by 7 inch tall. so about 0.26 cu ft.

Guess I'll have to start looking at suitable 8 inch mids first.

Regards,

Bart

mech986
05-01-2008, 02:26 PM
Here's a bit of an update:

I was able to contact the buyer of the remaining parts/drivers that were in these cabinets and have now obtained the crossovers that were in there, pics to follow over the weekend.

The crossovers are built on masonite boards with hot glued inductors and caps/resistors soldered onto riveted multi position terminal strips. Wires trail off to the UHF, HF, Mid and inputs respectively. Appears no provision for the low Freq. driver as yet so maybe it was a biamp which would fit with the 4 input terminals on the cabinet. There are only 2 8 ohmL-pads instead of 3. Mounting via typical JBL threaded inserts.

The wiring was marked with old masking tape for 2405, 2420, and LE8-T, which suggest which drivers they were - all alnico, and possibly prior to the Ferrite changeover? Interesting this unit would use the LE8T as a mid since its more optimized as a "full range" driver. So maybe built before the 2108 from the 4315 was available?

Also, took a good look at the crossover components - all have 5 digit JBL numbers but only could ID the caps and resistors - all the laminated core (3) and air core (1) inductors would not ID with current or past JBL Pro parts lists according to JBL Pro Parts.

Comparisoin with the 4340's 3140 schematic don't seem to correlate with the values seen there - JBL Parts suggested it may have been a one off, custom, or simplified version for consumer prototyping? Further investigatiion is needed and I'll have to finish reverse engineering the actual circuit and compare it to maybe cascaded scratch built versions of discrete crossovers like the 3105, etc.

I saw 3DB's post about the L400 prototype, wonder if this was some kind of early mule with an 8 instead of the 10? Makes one think...

More to come hopefully.

Regards,

Bart

tomee
06-23-2014, 02:43 PM
......
The wiring was marked with old masking tape for 2405, 2420, and LE8-T, which suggest which drivers they were - all alnico, and possibly prior to the Ferrite changeover? Interesting this unit would use the LE8T as a mid since its more optimized as a "full range" driver. So maybe built before the 2108 from the 4315 was available?

.....

I'm dragging up an OLD thread here..but... this sounds like a really cool find and I'm really curious about the crossover that was used with those drivers. What ever happened to these boxes?? Were they a JBL prototype, or a really advanced DIY project?
:)