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Thread: 4365 has quality problems

  1. #76
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    4365 might have been manufactured and/or stored in a humid environment.

    As far as I know, 4365 and the parts like 476Mg is assembled in Mexico.

    Is Mexico humid?

  2. #77
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    But I am not at all sure that humidity is the problem causing this.
    Might be something else.

  3. #78
    Senior Member Mctwins's Avatar
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    Ok, I have been thinking.

    We have to know for certain that it is the humidity in a room or a warehouse where the speakers are stored that is the culprit to the problem. There must be more speakers that have this problem. K2 uses the same driver.

    Or, can it be that it is due to excesive heat produced by to much(or low) power, amplifier goes into clipping. Thinking out loud here.

    We need more information from "they" who have problems.

    And, we need statement from a engineer from factory quality department to see what they have to say about it.

    All I can say is that I have been playing all day long yesterday pretty much at high volume(as usual), sounds great.

    It's been a while I have played with these speakers. Some four to six month have they been switch off.

    Don't worry, other brands besides JBL had some problems as well, very expensive audiophile loudspeakers.

    May the investigation continue...

  4. #79
    Senior Member Ian Mackenzie's Avatar
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    If you look on Japanese auction website the compression drivers images show actual brown rust on the mounting bolt circle that attaches to the horn. On eBay images of diaphragm terminals often show corrosion where screws attach the wires to the diaphragm. But that type of corrosion takes on the appearance of white oxide. That is moisture either between surfaces or trapped in the rear of the drivers.

    That is consistent with the hypothesis of moisture finding its way into the junction of two surfaces. However it could also be that as suggested the glue line or glue that had not full cured made contact with the edge of the phase plug on assembly. The glue has then reacted with phase plug. If it was moisture you would expect corrosion across the surface of the phase plug. But the marks of the corrosion or glue reaction are very defined.

    On the subject of humidity its a problem with optics where the lens is cold and is suddenly exposed to moist air. In the situation where the air is moist or humid and the metal is the same temperature you won’t see condensation on the metal. But if you cooled the room down quickly you would expect water in the form of condensation forming on surfaces.

  5. #80
    Senior Member 1audiohack's Avatar
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    Hi All;

    My 4365’s perform just fine. I am not going to take them apart. I live in the desert where lack of humididty is a problem.

    I will hazard a guess that this is a storage problem, based on an experience I had with some other new JBL’s I bought in the past.

    These were stored in their unopened factory boxes in the Northern California bay area for a while and when I brought them home, opened them up and stood them up, water literally ran out of the horn mouths. Drops, not a river but far more than just wet surfaces.

    It took me about two hours to scramble together the equipment and get the comp drivers under vacuum in a bell jar and almost 30 minutes each under high vacuum to get them completely dehumidified. Nearly a decade later they are still fine. These are Al drivers.

    Most the parts in these drivers are coated or plated with some sort of anticorrosion except the phase plugs which are zinc and fairly corrosion resistant. The aluminum diaphragms are alumaclad 2024 which has a very thin coat of pure aluminum which is very corrosion resistant and Be is corrosion resistant. Magnesium unfortunately is not corrosion resistant by itself.

    Bubbleboy mentioned the possibility of galvanic corossion where two types of metal react and while my experience with this is where these materials are in contact with each other like a bare steel part pressed into or threaded into aluminum there may be the possibility of electolytic effect if the zinc plating of the pole piece is connected with water to the magnesium.

    Short story with a disclaimer first: I have the utmost respect for Jerry Morro. I don’t know him well but liked him a lot.

    I had the privilege of speaking with him for a couple of hours at the Nothridge facility one day and he showed me a box of large format experimental diaphragms. Many lightweight metal aloys with many types of coatings. Of particular interest was a hard anodized aluminum diaphragm. This is where a coating of aluminum oxide is grown into and on the surface that is nearly diamond hard and actually reduces the weight of the part slightly. He said that they performed very well but failed quickly from fatigue at the bending area of the surround so it was one of the experiments that was abandoned.

    The one in my hand was completely anodized so I asked what I thought was the obvious question, “were they all like this or did you mask the surround on any?” (This would leave the surround still flexible)

    I could not tell from the look I got if it was either, of course you idiot, or damn, we didn’t think of that. But the look was enough fo me and I dropped it, and he didn’t answer. Pondering that on the drive home I didn’t think I remembered seeing any where the surround had been masked.

    In the end, nobody knows everything and maybe this corrosion thing was a possibility no one recognized or planned for.

    I haven’t done much with mag in a long time besides weld it. Are there corrosion inhibitors for it now? I guess we ought to look into it now that we have a reason. Magnesium is about to come into its renaissance in automotive production and this will have to be solved if it has not been already.

    On the is TJ humid? Depends where you are and which way the wind blows. It’s a big city by the coast.

    My best.
    Barry.
    If we knew what the hell we were doing, we wouldn't call it research would we.

  6. #81
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    Thank-You for your thoughts Barry on how this likely occurred ( it makes sense to me ).

    I've had compression drivers ( 2426's or 2425's ) get their gaps completely filled with water ( & to my horror ) haven't discovered this fact till a couple of months later ( the joys of using general cargo hauling across Canada ) .

    Needless to say the diaphragm coil-formers were ruined and the gaps were starting to rust very badly ( the zinc plating can only do so much to prevent rust when it's under water ).

    I saved my drivers by flushing the gaps out with penetrating oil ( WD40 ), then getting rid of all the rust and then re-immersing the gap for some time in oil ( before cleaning it all out /drying & finally installing new diaphragms ). This effort saved my drivers.

    Quote Originally Posted by Barry
    Most the parts in these drivers are coated or plated with some sort of anticorrosion except the phase plugs which are zinc and fairly corrosion resistant. The aluminum diaphragms are alumaclad 2024 which has a very thin coat of pure aluminum which is very corrosion resistant and Be is corrosion resistant. Magnesium unfortunately is not corrosion resistant by itself.
    So ( in your 4365's ) you've swapped out the original Mg types for Al diaphragms ?



  7. #82
    Senior Member 1audiohack's Avatar
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    Hello Earl;

    The hydro event was not with my 4365’s. They are still virtuous in their assembly.

    I too have bought “working” drivers that were badly water damaged. Like you I cleaned them up and then relegated them to general low expectation duty like shop stereo.

    It seems that to some people “working” means that the law of gravity still applies to it. If I only wanted a door stop...

    Barry.
    If we knew what the hell we were doing, we wouldn't call it research would we.

  8. #83
    Senior Member martin_wu99's Avatar
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    Quote Originally Posted by ngccglp View Post
    After reading this thread, it reinforced a principle , which is never to outsource critical components or process where you no longer have control of the quality. Many speakers manufacturers are still winding their own voice coils eg ATC.

    Hope HK/JBL stop this nonsense of just focusing on production cost.
    QC is always a big problem for those companies which have oversea factories.
    46 lover

  9. #84
    Senior Member martin_wu99's Avatar
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    Quote Originally Posted by bubbleboy76 View Post
    4365 might have been manufactured and/or stored in a humid environment.

    As far as I know, 4365 and the parts like 476Mg is assembled in Mexico.

    Is Mexico humid?
    Do you have any pictures of your 4365 crossover? please post out to show the difference between 4367
    46 lover

  10. #85
    Senior Member martin_wu99's Avatar
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    4367 crossover

    Quote Originally Posted by martin_wu99 View Post
    And more,one 4365 user said the components of 4365 crossover is very poor comparing with 4367,is that true?
    below is the pix of 4367's crossover
    4367 crossover
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    46 lover

  11. #86
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    What exactly is the problem with the 4365 crossover? "Very poor" is not a very good description of the perceived problem.

    There's a photo of the 4365 crossover in this pdf. It's large enough to be zoomed in quite a bit, enough to see that on the upper crossover section, all the capacitors are poly caps, no electrolytics. The inductors on both sections are air core, no iron core inductors.

    They look like nice units to me.

    https://www.jblsynthesis.com/tl_file...IO_MONITOR.pdf

  12. #87
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    There are fine components in 4365-crossover, as far as I know.
    The problem, to me, is that the HF part has no lowpass-filter. This causes HF to play the same register as UHF all the way up to 20KHz. This causes comb-filtering. 476Mg HF-driver does not roll off on its own.
    There is no proper acoustic crossover between HF and UHF.
    This makes 4365 sound and measure too bright for my taste. Listen on high volume and ears get fatigue after a while.

    But if this particular discussion should continue, do it in a new thread.

  13. #88
    Senior Member martin_wu99's Avatar
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    Quote Originally Posted by JeffW View Post
    What exactly is the problem with the 4365 crossover? "Very poor" is not a very good description of the perceived problem.

    There's a photo of the 4365 crossover in this pdf. It's large enough to be zoomed in quite a bit, enough to see that on the upper crossover section, all the capacitors are poly caps, no electrolytics. The inductors on both sections are air core, no iron core inductors.

    They look like nice units to me.

    https://www.jblsynthesis.com/tl_file...IO_MONITOR.pdf
    Thanks,a 4365 user complain that 4365's crossover is not as good as 4367's,so i want to know the truth.
    46 lover

  14. #89
    Senior Member martin_wu99's Avatar
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    Quote Originally Posted by bubbleboy76 View Post
    There are fine components in 4365-crossover, as far as I know.
    The problem, to me, is that the HF part has no lowpass-filter. This causes HF to play the same register as UHF all the way up to 20KHz. This causes comb-filtering. 476Mg HF-driver does not roll off on its own.
    There is no proper acoustic crossover between HF and UHF.
    This makes 4365 sound and measure too bright for my taste. Listen on high volume and ears get fatigue after a while.

    But if this particular discussion should continue, do it in a new thread.
    Is that so?that may be a problem,please post a new thread
    46 lover

  15. #90
    Senior Member baldrick's Avatar
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    4365 MF/HF filter.

    i really can’t understand that JBL did make a poor x-over design. Maybe they did not use absolute high END parts to svar Money. Are there LF filter on K2 or E2?
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