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Thread: JBL 476MG Diaphragm Issue

  1. #1
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    JBL 476MG Diaphragm Issue

    Hi,

    First of all happy holidays all.

    I do need extensive information about JBL 476mg High Frequency Driver's Diaphragm, I do have some performance issues with my drivers, and as I have figured it out that the main cause is the diaphragm, I have searched for a new driver but unfortunately they are very expensive so I decided to change the diaphragms, there are several genuine JBL diaphragm's on the market with the same ohm's (I have stated below), I wonder if they will fit like the same as original or not, or will it be problems with the new diaphragms, unfortunately there aren't so many information about 476MG but I have figured it out that JBL produced same kind of technical type of high frequency drivers like 476mg, just their other parts are different but it seems the diaphragm and the shell are the same for instance 476mg is very similar to 2452H-SL and I did my best to find the most suitable ones by searching from different sources. Any additional information or leading to the right source of information will be much appreciated.

    https://www.simplyspeakers.com/jbl-r...8r2452-sl.html
    https://reconingspeakers.com/product...2sl-diaphragm/
    https://www.ebay.com/itm/JBL-Factory...-/141197184095

    Thank you so much for the assistance.

    All the best.

  2. #2
    Administrator Robh3606's Avatar
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    What's wrong?? Are you having a corrosion issue?? That was reported on this forum a while back. You should be able to fit the 2450 family diaphragms in the 476 Core.


    The 476 Mg are 16 ohm drivers so if you have an existing crossover you will need to make changes!


    http://www.audioheritage.org/vbullet...76mg+corrosion


    Rob
    "I could be arguing in my spare time"

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    Quote Originally Posted by Robh3606 View Post
    What's wrong?? Are you having a corrosion issue?? That was reported on this forum a while back. You should be able to fit the 2450 family diaphragms in the 476 Core.


    The 476 Mg are 16 ohm drivers so if you have an existing crossover you will need to make changes!


    http://www.audioheritage.org/vbullet...76mg+corrosion


    Rob

    Actually no corrosion issue, one speaker started to play different than another, I have checked the crossover and other components but when I dismantle the drivers, the copper ring in the diaphragm was not in the same condition before somehow, so I wanted to change the diaphragm, it is very bad that ohm issue, I'm not sure I will be able to make changes on the crossover, I don't want the speakers to behave apart from the original, do you have any other diaphragm recommendation? By the way I again looked for my speaker's white paper, it has stated that the 476 MG's are 8 ohm's. (I have attached the screen shot of the white paper)
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    Administrator Robh3606's Avatar
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    What you have in the white paper is the DCR not the same. In general Impedance is about 2X the DCR value. Take a look at the 2452SL techsheet H vs J. What you need are 16 ohm SL or coated diaphragms. You should probably change both. Call the stores they may be able to order them for you or try to go through JBL for a replacement under warranty.

    http://www.audioheritage.org/vbullet...21706-2452h-sl

    Rob
    "I could be arguing in my spare time"

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    Quote Originally Posted by Robh3606 View Post
    What you have in the white paper is the DCR not the same. In general Impedance is about 2X the DCR value. Take a look at the 2452SL techsheet H vs J. What you need are 16 ohm SL or coated diaphragms. You should probably change both. Call the stores they may be able to order them for you or try to go through JBL for a replacement under warranty.

    http://www.audioheritage.org/vbullet...21706-2452h-sl

    Rob
    Rob, you are great! One additional question, is there a prediction that the sound will be the same as original? What should I do more to bring the speakers to the original condition?

  6. #6
    Senior Member pos's Avatar
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    The 476Mg use magnesium diaphragms that are different from the titanium ones listed above.
    Unless you manage to get your hands on magnesium diaphragms you will not get the same response as the original driver, and it will not work as intended.
    Maybe at this point the best thing to do would be to order a usb measurement mic to see what you currently have.

  7. #7
    Administrator Mr. Widget's Avatar
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    Do you have a JBL system with 476Mg drivers installed, or did you buy the 476Mg drivers for a DIY project? Either way can you get support from whoever you bought the speakers from?

    I do not think you can buy replacement Mg diaphragms. Unfortunately putting any other diaphragm in there will offer suboptimal performance. The magnesium diaphragms are extremely high performance units.


    Widget

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    Quote Originally Posted by Mr. Widget View Post
    Do you have a JBL system with 476Mg drivers installed, or did you buy the 476Mg drivers for a DIY project? Either way can you get support from whoever you bought the speakers from?

    I do not think you can buy replacement Mg diaphragms. Unfortunately putting any other diaphragm in there will offer suboptimal performance. The magnesium diaphragms are extremely high performance units.


    Widget
    Hi, I have a JBL system with 476MG installed, I have been having some sound issues tonal unbalance between midrange drivers, I found that the the copper ring on the diaphragm cause this problem (attached) I will not change the magnesium diaghpram in whole, I will only change the copper ring (attached) on the Diaphragm, I guess it will solve the problem, because of that, the matching copper ring will be suitable for me, I just need the suitable and %100 the same copper ring. You are right, I can't be able to buy mg diaphragms, they are sold as a whole driver. With the copper ring changed I think I will manage to solve the issue, what do you think?
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    Quote Originally Posted by pos View Post
    The 476Mg use magnesium diaphragms that are different from the titanium ones listed above.
    Unless you manage to get your hands on magnesium diaphragms you will not get the same response as the original driver, and it will not work as intended.
    Maybe at this point the best thing to do would be to order a usb measurement mic to see what you currently have.
    You are right, I just need to change the copper ring on it, this will solve the problem I guess, I have measured the drivers with a multi meter, they give the same ohm ratio, but the sound and the copper ring that I have attached before is different, I think that causes the unstablility with the two midrange drivers.

  10. #10
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by JamesBLansing View Post
    With the copper ring changed I think I will manage to solve the issue, what do you think?
    You are a braver man than I.

    This reminds me of the time I lived abroad and when the windshield wiper motor burned out in our car, we went to a repair shop and they rewound the motor. It never ran at exactly the same speed as before, but it worked. Ordering a replacement motor from the USA would have taken months and been quite costly.

    I would be hesitant to even remove the diaphragm from a modern JBL compression driver as they are precisely assembled and tested for performance. I suppose you can give it a try. Replacing the ring may be your best option if replacing the driver is not an option.

    Where is the copper ring?


    Widget

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    I think he means the voice coil?

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    Quote Originally Posted by Mr. Widget View Post
    You are a braver man than I.

    This reminds me of the time I lived abroad and when the windshield wiper motor burned out in our car, we went to a repair shop and they rewound the motor. It never ran at exactly the same speed as before, but it worked. Ordering a replacement motor from the USA would have taken months and been quite costly.

    I would be hesitant to even remove the diaphragm from a modern JBL compression driver as they are precisely assembled and tested for performance. I suppose you can give it a try. Replacing the ring may be your best option if replacing the driver is not an option.

    Where is the copper ring?


    Widget
    )), Sometimes absence can make us do brave or silly things, I have to remove the diaphragm, and fix the copper ring on it because as you have seen from the pictures, they are damaged, and because of that, there is a %20 sound difference between the two drivers, and unfortunately I always hear the difference when I'm listening, I tested the crossovers, but they are the same and they all fine, I tested the woofers but they are the same also, I tested the uhf's, they are the same, just one difference in the system, that is midrange drivers so to speak "HF", when I opened the driver and see the diaphragm, I saw that the copper ring is fixed before, because of that I think this became a problem. ı don't want to make a deep renovation on the drivers but I couldn't find any other option, ı will to my best to keep them in original shape, I also got in touch with the JBL Dealer but they are selling the whole driver for nearly around 4.000 dollars each!, so I'm searching for the best suitable option. I have been searching for nearly one week, and I came across that 476 MG has huge similarities with other JBL drivers apart from their white papers, for instance the HF drivers of JBL 5732 cinema speakers seems identical with 476MG's.

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    Quote Originally Posted by JeffW View Post
    I think he means the voice coil?
    yes sorry for the non technical terms, voice coil.

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    Quote Originally Posted by Robh3606 View Post
    What you have in the white paper is the DCR not the same. In general Impedance is about 2X the DCR value. Take a look at the 2452SL techsheet H vs J. What you need are 16 ohm SL or coated diaphragms. You should probably change both. Call the stores they may be able to order them for you or try to go through JBL for a replacement under warranty.

    http://www.audioheritage.org/vbullet...21706-2452h-sl

    Rob
    Hi Rob

    Do you think that the 2452SL's diaphragm is identical with 476 mg?

  15. #15
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by JamesBLansing View Post
    yes sorry for the non technical terms, voice coil.
    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

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