JBL 476MG Diaphragm Issue

[JamesBLansing]

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.

[Robh3606]

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

[JamesBLansing]

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)

[Robh3606]

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

[JamesBLansing]

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?

[pos]

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.

[HCSGuy]

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.

[JamesBLansing]

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?

[HCSGuy]

Quick recap - you are in the UK and your speakers are a “few” years old. First, what is the JBL warranty for the UK - you may have to call the UK importer of JBL to find out. Second, as Widget said, the JBL warranty starts from when a current model speaker is invoiced to the final user - it does not matter if the speaker was used as a dealer demo for 2-3yrs. I am sure, however, that JBL would balk at a warranty repair on a speaker that has been out of production for quite some time, e.g. a speaker that was discontinued 10yrs ago cannot reasonably still be under warranty, just as JBL can’t still be held responsible for the speakers my father bought in the 60’s that had their old “Lifetime” warranty. The worst case in this scenario is that your dealer did not sell you Demo speakers, but instead resold you speakers he had bought back from someone else towards an upgrade - either originally purchased from him, or elsewhere. Either way, he can pursue a warranty claim on your speakers until it is rejected by JBL. I think you have much further to go on pursuing your claim here.

How do you know the problem is the driver? First, you need to carefully re-assemble your driver and listen to it. If that speaker still sounds off, make sure the alignment of the driver to the horn does not have any way to be shifted off, then swap just the 476mg from that speaker to the other speaker, then listen to them both again - did the bad sound follow the suspect driver (Driver is bad), or did it stay with the original (crossover may have a problem). Above all, as Widget said, DO NOT pull the diaphragm out of the good driver. If the bad sound stays with the driver, and you exhaust your efforts with JBL, then I would talk to Guido or find a really good speaker tech in UK or EU to send both drivers to, and have them test the bad driver and see if the diaphragm to driver fitment can be improved. If all that fails, which it shouldn’t, PM me about a replacement pair of drivers.

[JamesBLansing]

Quick recap - you are in the UK and your speakers are a “few” years old. First, what is the JBL warranty for the UK - you may have to call the UK importer of JBL to find out. Second, as Widget said, the JBL warranty starts from when a current model speaker is invoiced to the final user - it does not matter if the speaker was used as a dealer demo for 2-3yrs. I am sure, however, that JBL would balk at a warranty repair on a speaker that has been out of production for quite some time, e.g. a speaker that was discontinued 10yrs ago cannot reasonably still be under warranty, just as JBL can’t still be held responsible for the speakers my father bought in the 60’s that had their old “Lifetime” warranty. The worst case in this scenario is that your dealer did not sell you Demo speakers, but instead resold you speakers he had bought back from someone else towards an upgrade - either originally purchased from him, or elsewhere. Either way, he can pursue a warranty claim on your speakers until it is rejected by JBL. I think you have much further to go on pursuing your claim here.

How do you know the problem is the driver? First, you need to carefully re-assemble your driver and listen to it. If that speaker still sounds off, make sure the alignment of the driver to the horn does not have any way to be shifted off, then swap just the 476mg from that speaker to the other speaker, then listen to them both again - did the bad sound follow the suspect driver (Driver is bad), or did it stay with the original (crossover may have a problem). Above all, as Widget said, DO NOT pull the diaphragm out of the good driver. If the bad sound stays with the driver, and you exhaust your efforts with JBL, then I would talk to Guido or find a really good speaker tech in UK or EU to send both drivers to, and have them test the bad driver and see if the diaphragm to driver fitment can be improved. If all that fails, which it shouldn’t, PM me about a replacement pair of drivers.

Thank you for the detailed answered, sorry for the late reply, I have been dealing with health issues, for the JBL warranty issue, unfortunately I can't be able to take any action so I have cut my own rope.

I have tried swapping the drivers, same result, I have measured all the crossover capacitors - the crossovers give the same ratios, I have measured all the drivers - they gave the same ohm ratio, I have tried listening all the drivers seperately together - same result, I happen to hear a tonal difference between two HF drivers, I also believe the driver is ok but then the problem will be with the crossover, I think I need to check the crossovers with a good technician, I need to find the problem but unfortunately I couldn't so far