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Thread: JBL 476MG Diaphragm Issue

  1. #16
    Senior Member pos's Avatar
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    What make you think the voice coils are damaged?
    I don't see anything obvious from the picture above.

    At this point you should probably send the drivers to some competent shop and have them clean and reinstall everything correctly.

    What is the history of these drivers? Did you get them new? Did you remove the diaphragms before?
    Proper installation and centering is paramount here...

  2. #17
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    Quote Originally Posted by Mr. Widget View Post
    Oh geez!

    Yes, it can be replaced, but the response will never be right.

    Can you sell the pair of 476Mg drivers, and buy a matched pair of anything else? The only way you’ll be able to use this pair of drivers, you’ll need to ruin the good driver so they both have matching diaphragms.


    Widget
    Unfortunately I can't , I don't want to ruin my 4365's, because of that I'm searching for everyway possible.

  3. #18
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    Quote Originally Posted by pos View Post
    What make you think the voice coils are damaged?
    I don't see anything obvious from the picture above.

    At this point you should probably send the drivers to some competent shop and have them clean and reinstall everything correctly.

    What is the history of these drivers? Did you get them new? Did you remove the diaphragms before?
    Proper installation and centering is paramount here...
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    The drivers are my 4365's drivers, which I have bought from a dealer as a demo product nearly 2 years ago, 3 months ago I have noticed that two speakers are playing differently both in mono and stereo soundtracks, I have checked all the options (there can be other also), because I have another pair of speakers which are 4367, with listening them all, I can easily say that 4365's are behaving not normally than it should be, I also have checked the attenuators of hf and uhf's but no solution, when I checked the driver that sousing the problem, I noticed that the voice coil had some operation (it can't be factory original in my opinion) if this voice coil is the factory original than I will have relief, and have another search only for the crossovers because there won't be any other option I guess, in order to give you detailed information I have attached additional photos of the diaphragm and voice coil, thank you for the responses and informations, I will be grateful if I know that I have missed a crucial point since I know JBL speakers very well and been using for nearly 20 years but in deep technical knowledge I have some gray areas.Name:  IMG_5705.jpg
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  4. #19
    Senior Member grumpy's Avatar
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    Thinking outside the box a bit... TruExtent Be diaphragms might at least get you a matching pair... probably less than 1/2 your new driver quote.
    Would take some serious homework to make sure they'd be suited for a 476Mg diaphragm swap out, but an option to consider. Someone here has probably run response curves for both...
    Sorry if this was suggested earlier... came late to the party.

  5. #20
    Senior Member HCSGuy's Avatar
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    If they were purchased legit, through a JBL dealer, wouldn’t they still be under warranty? Abuse not included, JBL should have a remedy, and I don’t see anything that suggests a melted voice coil.
    That the internet contains a blog documenting your life does not constitute proof that your existence is valid. Sorry.

  6. #21
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by JamesBLansing View Post
    Unfortunately I can't , I don't want to ruin my 4365's, because of that I'm searching for everyway possible.
    I agree with you. The 4365 is a great speaker and should not be modified. I did not realize that you were using actual JBL speakers… any departure from the original factory built 476Mg will be a terrible thing.

    Quote Originally Posted by HCSGuy View Post
    If they were purchased legit, through a JBL dealer, wouldn’t they still be under warranty? Abuse not included, JBL should have a remedy, and I don’t see anything that suggests a melted voice coil.
    In the USA and probably everywhere else, demo or not, they should have a 5 year warranty. I would ask the dealer to repair them at no cost and if he refuses to help you, find the Harman importer for your country and demand they repair them.



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  7. #22
    Administrator Robh3606's Avatar
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    Here is a brand new DR82450SL and mine looks almost the same. You have to remember that you are dealing with a flat ribbon that gets twisted from the opposite side and gets twisted again to make a solder connection. One side is coming from the opposite side of the coil and that's the one I have a picture of. The other side looks much better because you only have to twist it 90 degrees to make the solder connection. Granted either one of them are not pretty but they pull this of in what a .025 gap!

    You might just have a simple alignment issue/screw torque. When you took out the diaphragm did you notice if some of the screws were easier to break the torque on?? I once have a driver where one of the screws was "loose" and once I retightened it was fine again. JBL should help you with this.

    Rob
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  8. #23
    Senior Member grumpy's Avatar
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    JBL should help you with this.
    Seriously. Anything else is last-resort kind of stuff for a factory system.
    Hope there is some success with the dealer, etc... that would be fantastic.

    Off topic:
    I need to get back into a mode where I can test drivers again, as now I'm curious
    how well the aftermarket Be with the rolloff (vs the 476Be) tracks the 476Mg.

  9. #24
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    Quote Originally Posted by Robh3606 View Post
    Here is a brand new DR82450SL and mine looks almost the same. You have to remember that you are dealing with a flat ribbon that gets twisted from the opposite side and gets twisted again to make a solder connection. One side is coming from the opposite side of the coil and that's the one I have a picture of. The other side looks much better because you only have to twist it 90 degrees to make the solder connection. Granted either one of them are not pretty but they pull this of in what a .025 gap!

    You might just have a simple alignment issue/screw torque. When you took out the diaphragm did you notice if some of the screws were easier to break the torque on?? I once have a driver where one of the screws was "loose" and once I retightened it was fine again. JBL should help you with this.

    Rob
    Oh! that is a relief!, maybe that won't be a problem with the diaphragm, I will check the screws again, and I will change the diaghraphms between the speakers, to see whether I will have a difference or not, once a technician said that these horn drivers have some special liquid in it, and the liquid can cause sound differences, is there a thing like that? can it be the problem?

  10. #25
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    Quote Originally Posted by grumpy View Post
    Seriously. Anything else is last-resort kind of stuff for a factory system.
    Hope there is some success with the dealer, etc... that would be fantastic.

    Off topic:
    I need to get back into a mode where I can test drivers again, as now I'm curious
    how well the aftermarket Be with the rolloff (vs the 476Be) tracks the 476Mg.
    You are right but, I spoke with the dealer, and they requested to change the whole driver, unfortunately the parts of the driver isn't sold by JBL

  11. #26
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    Quote Originally Posted by grumpy View Post
    Thinking outside the box a bit... TruExtent Be diaphragms might at least get you a matching pair... probably less than 1/2 your new driver quote.
    Would take some serious homework to make sure they'd be suited for a 476Mg diaphragm swap out, but an option to consider. Someone here has probably run response curves for both...
    Sorry if this was suggested earlier... came late to the party.
    You are right!, I'm very careful not to ruin the original drivers, since I have learn the exact problem, maybe it is not with the drivers, maybe it is the crossover, since I have measured all the parts of the crossover and they measure the same as factory crossover schematic, I don't what I should look further?

  12. #27
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by JamesBLansing View Post
    You are right but, I spoke with the dealer, and they requested to change the whole driver, unfortunately the parts of the driver isn't sold by JBL
    I am also JBL dealer. Replacing the driver is the correct repair procedure for this model. JBL will replace a defective driver at no cost as a warranty repair. YOU should NOT be opening up the driver however, this may void your warranty! When your dealer provides the serial number of your 4365 and tells JBL that there is a warranty issue, he can order a replacement 476Mg.

    ALSO, DO NOT SWAP THE DIAPHRAGMS! DO NOT OPEN THE GOOD DRIVER!!!


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  13. #28
    Administrator Robh3606's Avatar
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    Off topic:
    I need to get back into a mode where I can test drivers again, as now I'm curious
    how well the aftermarket Be with the rolloff (vs the 476Be) tracks the 476Mg.
    Hello Grumpy

    The 476Mg runs out past 20K on the M2 waveguide and is clean on a CSD. It doesn't have the all the "noise" from the secondary resonances that the Ti diaphragm's have. The Be are also clean but don't have the extension that the Mg's have. In his speakers they run out the 476MG's and add a tweeter above.

    If he goes to Be he will probably have a dip in response. If you look at the schematic the UHF trim is done by rolling off the 476Mg driver and diaphragm swaps would be a very risky proposition as far as keeping the original frequency response.

    Rob
    "I could be arguing in my spare time"

  14. #29
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    Quote Originally Posted by Mr. Widget View Post
    I am also JBL dealer. Replacing the driver is the correct repair procedure for this model. JBL will replace a defective driver at no cost as a warranty repair. YOU should NOT be opening up the driver however, this may void your warranty! When your dealer provides the serial number of your 4365 and tells JBL that there is a warranty issue, he can order a replacement 476Mg.

    ALSO, DO NOT SWAP THE DIAPHRAGMS! DO NOT OPEN THE GOOD DRIVER!!!


    Widget
    I have already contacted with a dealer since my speaker is from 2013 it is out of warranty, the main purpose is not to ruin the original drivers, I'm still thinking that there is no problem with the driver, since Rob send the diaphragm pictures of his speaker and I'm convinced, I must find the problem of the unstability of the midrange sounds between two speakers, I have tried several options but right now I couldn't find the issue.

  15. #30
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by JamesBLansing View Post
    I'm still thinking that there is no problem with the driver, since Rob send the diaphragm pictures of his speaker and I'm convinced, I must find the problem of the unstability of the midrange sounds between two speakers, I have tried several options but right now I couldn't find the issue.
    I wouldn't expect to be able to see a problem by looking at it. Sometimes you can, but often an out of spec driver looks perfect.


    On diving in and playing Rambo with your drivers.

    Let's say you have a pair of identical Rolexes. If one was keeping poor time, would you pull the main spring out of one to test the other? Even if you are quite handy, I would expect you would end up with two watches that were not quite right or perhaps worse.

    In the past JBL sold replacement diaphragms that trained repair facilities could swap out. Today the drivers are less forgiving so most do not offer this as an option and the repair procedure is a driver swap. Yes, out of warranty it is expensive, but if you own a "finished goods" JBL speaker you are entitled to have access to replacement drivers.

    On the warranty.
    In the US the warranty begins with the first sale to the end user and not the date of delivery to the dealer. I assume it is the same in your country.

    If I bought a pair of new or demo JBLs and had issues I would be on my dealer and demand satisfaction regardless of the "bargain" he may have struck with me at the time of sale.



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