Seeking guidance on JBL 4312A woofer issue

[bjgrant]

Good evening all. I have a pair of 4312A control monitors that I have cherished for nigh on to 40 years. Recently loaned one out to a young musician friend and it has been returned with a dead woofer. Totally dead. I isolated the woofer and tested the tweeter and mid-range speakers independently as well. All are fine except the woofer. I know he was testing a Gallien-Krueger bass amp power head with this cabinet. I tested the amp later and it seemed to be defective, putting out what sounded like a loud square wave at random intervals. I presume the woofer is beyond help but I wanted to know if anyone has any thoughts that might help. It looks pristine externally. I might suspect the voice coil is welded or something equally dreadful. Can I fix this? Or just replace? Any help much appreciated. I so love these speakers. Thanks.
BG

[Mannermusic]

Good evening all. I have a pair of 4312A control monitors that I have cherished for nigh on to 40 years. Recently loaned one out to a young musician friend and it has been returned with a dead woofer. Totally dead. I isolated the woofer and tested the tweeter and mid-range speakers independently as well. All are fine except the woofer. I know he was testing a Gallien-Krueger bass amp power head with this cabinet. I tested the amp later and it seemed to be defective, putting out what sounded like a loud square wave at random intervals. I presume the woofer is beyond help but I wanted to know if anyone has any thoughts that might help. It looks pristine externally. I might suspect the voice coil is welded or something equally dreadful. Can I fix this? Or just replace? Any help much appreciated. I so love these speakers. Thanks.
BG

It's an "R&R." Did the same a few years ago with a 4312. In my case, the voice coil actually jumped the gap. See your local JBL pro - last I looked the kits were still available. It happens.

[bjgrant]

It's an "R&R." Did the same a few years ago with a 4312. In my case, the voice coil actually jumped the gap. See your local JBL pro - last I looked the kits were still available. It happens.

R&R? I do not know the acronym. Can you please explain? I am interested in this kit you mention; where do I find it and procedures for rebuilding? Sorry I have been out of audio engineering for decades and doing data networks, computing based technologies for too long. I need to get back to the fun stuff. Thanks in advance for any additional info you may provide.

BG

[Mannermusic]

R&R? I do not know the acronym. Can you please explain? I am interested in this kit you mention; where do I find it and procedures for rebuilding? Sorry I have been out of audio engineering for decades and doing data networks, computing based technologies for too long. I need to get back to the fun stuff. Thanks in advance for any additional info you may provide.

BG

Remove and Replace. i.e. no simple fix, needs to be reconed. But, that is why you need to take the woofer to a JBL pro shop - they have the reconing kits and tools/know-how. Do not usually sell kits for user installation in order to assure JBL specifications / factory warranty. You can Google JBL Pro for the nearest shop - there is a Web page with geographical locations of all the JBL shops. In my case, they did the job in two days and it was as new. Also, there is always ebay and that is a fairly common woofer. Your choice. Mike

[bjgrant]

Remove and Replace. i.e. no simple fix, needs to be reconed. But, that is why you need to take the woofer to a JBL pro shop - they have the reconing kits and tools/know-how. Do not usually sell kits for user installation in order to assure JBL specifications / factory warranty. You can Google JBL Pro for the nearest shop - there is a Web page with geographical locations of all the JBL shops. In my case, they did the job in two days and it was as new. Also, there is always ebay and that is a fairly common woofer. Your choice. Mike

Thanks Mike.

[Mannermusic]

Hi BG, you're welcome. Are you "up and running?" I recall that mine was approx $200 - good for another 40 years! Mike

[robertbartsch]

.....the other option would be to buy two used woofers in good condition. They often appear on Feabay. I would re-do both woofers at the same time...

[brettMc]

Hi All,

I am a proud owner of a nice pair of JBL 4312a control monitors....and a proud owner of 4408's and 4406's as well. I love all of them but really dig the 4312a's. However I have to say they are harsh and unforgiving. There is an upper-mid or low-high frequency that comes off the woofers that drives me up a wall. I can dial down the midrange and the tweeter and the frequency that bigs me is definitely coming off the large cones. Can anyone tell me why or what I can do about it? One of them was professionally roconed all JBL parts. Everything seems to be in working order. Do I maybe need to replace the capacitors? Is there a known 'diffraction' that comes of them big ridged paper cones? I've had to resort to draping some fabric over the cones to reduce this frequency.

Perhaps someone could suggest a nice tube amp that would play well with these?

I am using a tube-based modwright Oppo as my digital playback source. Emotiva amp.

Any advice would be greatly appreciated.

Thanks,
Brett