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Thread: Discussion Thread JBL 4343 to 4344 upgrade

  1. #46
    Senior Member saeman's Avatar
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    Quote Originally Posted by Ian Mackenzie
    Well some how you will need access to the compression driver and slot otherwise it will be almost impossible to remove the driver if it requires servicing. The same applies to the 2405.
    Ian: I've never been a fan of a screwed down baffle. The two pairs of 4343's I've owned had their upper baffle sections removed some unknown number of times. The screw holes were deeply recessed into the wood and after a while the screw threads get stripped out. Removable rear panels remind me of most of Altec's cabinets, not made near as well as JBL's. The enclosure integrity is always at stake. Sealing tape is required and it just seems like a hassle.

    Consider this option - My baffle is very similar to the one you posted in this and other threads on the 4344. Between the compression driver and the woofer cutout there sits the big obstacle of the mid-base box. You can however take the driver/horn in hand and reach around the mid-base box. If one lacks the arm strength to lift/hold it into place until the screws are installed there's another little trick I learned from other projects. With one hand put the horn in position and using the other hand reach thru the cutout and stand it up under the hole. Take two pieces if 1/4-20 threaded rod with an "L" bent on one end and insert them thru two of the 4 mounting holes in the baffle and screw them into the horn. Then use the rods to pull the assembly up into place. Put the two opposite screws in, remove the rods and install the other two screws. The 2405 presents no problems with your baffle layout.

    Is all of this anal - maybe to some. Building a box with all panels glued and screwed solid and doing business thru the baffle cutouts is always a better choice. Looking at everything JBL made I'm sure that this method was their first choice. If you don't have strong kids with long arms to help you can always bend up a couple pieces of threaded rod and do it by yourself. Coz the kids aren't always home I have rods too.

    Take a close look at my 4351 baffle layout and see if you can figure out how I can get the 2440 and 2405 in and out of the cabinet, based on where they are located relative to the mid-base box and the duct tubes.

    Not trying to be a smart ass but if there's anyway you can get around building an enclosure with removable panels - you should do it. My 4351's were a challenge in this arena. Rick

  2. #47
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    I suppose that would work.

    In the drawings I posted there is a rear panel bracing.

    I used this in my own 4345 clone and there are no issues with integrity of the enclosure. I use furniture grade flat head bolts with captive screw-in inserts in the hardwood frame to pull the removeabe baffle hard down on the medium density rubber gasket.

    The removable baffle is about 12 inches high x the width of the enclosure. In fact I would say with this particular arrangement where there are two vertical 1x 3 inch braces and a 2 x 3 inch cross brace and also 2 front to rear braces adjoining the Dog Box and the rear panel make it more inert than a single large baffle......but whatever......

    Ian

  3. #48
    Senior Member saeman's Avatar
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    4344

    Hello Ian: I finished looking over your drawings and have extracted the info I need. Will try to start cutting some wood here soon. Although I'm not fond of having the rear panel removable, I do like the thought of a removable panel section and the framing necessary to provide it does beef up the rear panel. My 4341's have an upper removable panel to allow access to the mid and hi drivers. It is tastefully done and the cabinet rear is still good and solid. I'll chug along with the project and see where I end up. The cabinets are the easy part. Still need to locate some of the components (the 2122's should be easy to find, growing on trees I hear - ah, um, blah, ???, etc.) and will also try to work with someone more knowledgable than I am to get the x-overs built. I suspect this will be an on going and long term effort. I appreciate your comments and will keep you posted as I progress. Thanx - Rick

  4. #49
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    Rick,

    At this early stage we are merely gathering opinions, data and resources, pop in and say hello as you please.

    As each stage or step in the frame work is completed in the bhow to guide permanent data will be posted to the design thread.

    Obviously members will pick up the project as you have done at a particular point and we wll do our best to accommodate you needs. We plan to progress through the steps as previously advised as this is the most logical approach.

    Ian

  5. #50
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    One of the things I am mindful of is the question "what can I expect from these changes" particularly in reference to steps 5, 6 and 7. And not everyone one will be keen to starting making updates without some knowledge of the gains or improvements.

    This has not been an easy issue to provide specific answers on so we been doing some very interesting tests and comparisons.

    First off, we need to look at the 4343 in terms of its have's and have not's and in order to see what is going on in the system this means operating it at its basic level. This means full passive mode.

    So Ed and have been doing some listening comparisons to arrive at some conclusions and applying the results to the technical side.

    Step 4 has not been fully explored however working on the premise that good terminations are vital any unnecessary switches should be removed from the signal path.

    To test this I placed a heavy duty jumper lead with crocodile clips in series with the positive input to the crossover network and did some blind test comparisons.

    The cable was pure OFC and terminated to a Cardas hi quality binding post.
    Inserting the jumper lead in series with the crossover and the amps caused a loss of low level information and the sound stage collapsed and sounded flat and planar.

    So, while cables are often the flavour of the month in audiophile chat rooms please be aware that it's the terminations that are the final arbitrator of conductivity. Hence, a switch or other brass contact, oxidised or otherwise will downgrade the purity of the signal. Think of the amp as your car battery and the speaker as the starter motor.....its a good analogy.

    Good terminations...we will discuss this in more detail in step 4.

    Step 5. Upgrading the stock crossovers. This is the most popular issue and also the most expensive and controversial update for anyone contemplating a speaker restoration or a new design.

    Again, we have organised some comparisons and have come to some conclusions. Some of these comparisons were conducted with the 4343 system and others simulated using the reference system the 4345.

    Specifically in the 4343 the 3143 crossover has the midrange, horn and slot signal routed via a 52 uf capacitor in the midrange bandpass filter.

    This was done according to JBL to improve the protection to the compression driver and slot from amplifier turn on/off transients. In the early days this was a problem but with modern amplifiers it is far less of an issue.

    In a recent comparison with the reference system I was able to determine that the arrangement of this capacitor does cause a loss on information to the compression driver and slot. Specifically a loss of ambience and very fine details....much like a more polite but otherwise muted sound that lacked snap and dynamics. The series capacitor was a Solen polypropolyne metalised film foil bypassed with a 0.1 Solen film and foil capacitor (not charge coupled). The amplifier used was a Passlabs Aleph design.

    By removing the capacitor entirely and putting the system in bi amp mode using a very special, and hi quality active crossover we also observed marked improvements in midrange clarity, transparency and improved purity. This was very noticeable on vocal harmonies where individual voices could more easily be identified. The active crossover used in this comparison is a discrete class A unit with a Passlabs Aleph amplifier on the highs and a PSS 600 amplifier on the lows.

    We also observed that the 4343 in full passive mode can perform better than in active mode and the determining factor here is the performance of the active crossover and the amplifiers. Again a loss of information lead to less realistic results in biamp mode while the bass was more detailed ahd more authority in bi amp mode. The crossover used in this comparison was the Ashly analogue unit using a Passlabs X 250 amplifier on the lows and Mac amplifier on the highs. A Passlabs X 250 amplifer used in full passive mode.

    So we can see that by reviewing the crossover network, the manner in which it is arranged and the use of a hi quality active crossover will yield a net improvement in musical performance.

    Details of various upgrades will be discussed in step 5.

    Step 6 Biamping Pros and Cons

    Refer to step 5. The pros are improved bass clarity and authority. The cons are loss of transparency, imaging and information. The extent of the later will depend on the active crossover in use. Analogue active crossovers a deemed better and more affordable for home use than pro audio digital active crossovers. However budget prices will only buy budget performance in both cases.

    Crossovers available on the Market.

    Well there are dozens from entry level units like the Ashly, the JBL 5235, the Bryston and the Passlabs. The last 2 are premium grade but aren't cheap. Please note 4343-4343 does however require a specific crossover characteristic in order that the system works correctly.

    I may be enticed to assist with providing a customised crossover with appropriate performance to interested parties. Pm me for details.

    Step 1, 2 and 6

    Surprisingly drivers to deteriorate with age,particularly the compression driver diaphram. Have it check by an authorised JBL agent/reconer.

    There in an improve driver/diaphragm used in the 4344...the 2425J and there is rare aluminium versions of the diaphram seen on Ebay.

    While is had previously built a cloned 4343 its on on sight for direct comparison with updated driver. The 2425J is a superior a driver and the aluminium variant of the diaphragm sort after.

    Many have trouble taming the horn in the 4343, I think this is one of the biggest issues with the 4343. The solution is a mix of driver, crossover upgrade and careful setup.

    I have used both the 2231A and the 2231H and 2235H. There are differences in power handling and subtle differences in performance. The 2121 and the 2122H are different beasts. I have not A/B'd them so I can't comment. The 2122H does however require a different passive crossover.

    We will discuss this in more detail later and perhaps other members can post there experiences with driver updates.

    Summary

    As mentioned in an earlier post it is important to view the loudspeaker as a system. That is the sum of all the parts of the system come together to create the desired level of performance.

    In order to obtain the maximum potential from the loudspeaker we must therefore look critically at each part of the system and decide what updates are required and "how" to implement those updates.

    From our investigations we have identified the 4343 system in its raw state is far from capable of producing the maximum potential of its performance. Care needs to be taken when introducing ancilary equipment like active crossovers or graphic equalisers, as they could well be hindering rather than providing a net gain to attaining the maximum potential performance from the system.

    The purpose of this post was to give some degree of indication on the net effect of these updates.

    Ian



  6. #51
    Tom Loizeaux
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    p.s. for the sake of new members who are starting to discover this site, it would help if those of you who have been around for a while not spoil it for us with comments like, "we've discussed this so many times before." it's dissappointing when a thread is prematurely ended...it's all new to me.[/QUOTE]

    I agree that, though some things seem obvious or have been discussed to where we think it's "common knowledge", we should try to make these "4343 to 4344 Upgrades" postings as thorough as possible.
    I, for one, plan on printing out the succinct pages for a file on this subject...for studying later!

    Thanks again, Ian and others, for getting this thread going.

    Tom

  7. #52
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    Tom,

    I think that has been rectified.

    Ian

  8. #53
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    4344 Baffle

    Ian: Took a crack at cutting one of my 4344 baffles - 1" P.B. with the mid-base box out of 3/4" P.B. The component layout is similar to the design you posted, with drivers in vertical alignment and non-equadistant to any of the cabinet walls. I moved the ducts down a bit to allow access to the upper internal area for installation of the mid range driver thru the woofer cutout. The other one will be a mirror image of this one. Before I cut the next one - your comments please. Duct tube length is still evading me. Combed thru many many posts and am finding nuttin.

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  9. #54
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    Looks good Rick

    The main thing is to make sure everything fill fit together.

    ie the drivers, dog box etc will clear any internal aspects on the main enclosure.

    Remember there is a brace for the horn driver.

    If you plan to make te front baffle permanent why not use the side wall as the enclosure wall for the Dog box!

    Ian

  10. #55
    Senior Member saeman's Avatar
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    Quote Originally Posted by Ian Mackenzie

    Remember there is a brace for the horn driver.
    BRACE FOR THE HORN DRIVER ????? What brace ?? I was not aware of this. Is it something like that used to support the weight of the 2440 in the 4350 ?? Or is it a cradle that holds the end of the motor like that used in the 4331/4333 ???

    If you plan to make te front baffle permanent why not use the side wall as the enclosure wall for the Dog box!
    Ian
    I had planned to use two 1 1/2" x 2 1/2" braces, front to back on each side panel. Moving the dog box full right, with it's own side panel, will take the place of the two side braces on one side of each cabinet. After assembling the cabinet I'll go in thru the mid-base cutout and screw the dog box wall to the cabinet side (glue between the two).

    Thanks for chiming in. Rick

  11. #56
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    Quote Originally Posted by riessen
    BRACE FOR THE HORN DRIVER ????? What brace ?? I was not aware of this. Or is it a cradle that holds the end of the motor like that used in the 4331/4333 ???

    YES



    I had planned to use two 1 1/2" x 2 1/2" braces, front to back on each side panel. Moving the dog box full right, with it's own side panel, will take the place of the two side braces on one side of each cabinet. After assembling the cabinet I'll go in thru the mid-base cutout and screw the dog box wall to the cabinet side (glue between the two).

    Thanks for chiming in. Rick
    Okay

    Ian

  12. #57
    Senior Member saeman's Avatar
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    Ian: Tell me about this brace that supports the mid driver. Does it attach to the driver? Is it a cradle to support weight?? I didn't see anything in your drawings. There isn't anything in the 4343's. Was this new to the 4344?

  13. #58
    Tom Loizeaux
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    riessen

    Quote Originally Posted by riessen
    ... Duct tube length is still evading me. Combed thru many many posts and am finding nuttin.
    The duct length on the stock 4343s is 8 1/4" for each tube.

    I think your work is great! You've come up with a subtle, but definite improvement.
    If it were me, though, I think I'd place the 2405 slot directly above the 2420... making a slightly taller cabinet. I like the high end to be up to head level when ever possible.
    Great work!

    Tom

  14. #59
    Senior Member saeman's Avatar
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    Quote Originally Posted by Tom Loizeaux
    The duct length on the stock 4343s is 8 1/4" for each tube.

    I think your work is great! You've come up with a subtle, but definite improvement.
    If it were me, though, I think I'd place the 2405 slot directly above the 2420... making a slightly taller cabinet. I like the high end to be up to head level when ever possible.
    Great work!

    Tom
    Hi Tom: Thanx much for your comments. I agree with you on having the 2405 on top and I struggled with the idea and decided not to do it. I have in the past, built tall towers for the express purpose of getting the components up off the floor and projecting into the listening area better. Since I'm calling these 4344's I'm gunna make them look exactly like those built by our buddy James. One exception - since they're never going to be hung or layed on their side, I'm going to mount them on a base and I'm thinking of angling the base so that they tilt back 3-5 degrees. For my intended listening area this should help to better disperse the highs. We'll see. Regards - Rick

  15. #60
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    With the slot on top the dilema is its the narrow vertical polar pattern.

    With the slots on the side/outer the action of the crossover polar geomtry is to angle the 8K frequencies and above towards the listening in the middle.

    Ian

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