View Full Version : replace throat on 375

05-01-2003, 01:00 PM
Has anyone taken apart a 375 or any other JBL comp.drivers?I need to replace the broken throat,I have the part,it looks like they use a press fit to put together the driver but I'm not sure,if I can get it apart I can take care of the rest,JBl tech has told me it can be done but they would like me to send it in,but at a cost over $300,I'm ready to take the hammer out to see what this baby is made of,any help would be greatly app.by the way I do have pics of a 075 completely disassembled/then reassembled in working condition.I got the 075,in less than working condition-it was dropped,but after taking it apart,recentering the gap,it worked fine-good learning experience:D

Earl K
05-01-2003, 05:23 PM
Hi jblwolf

Sharp blows to alnico magnets ( such as hammer blows ) are known to demagnetize these magnets. The result is a noticable drop in output level in the top end & sometimes an overall drop across the whole spectrum . Then a remag is a must. That's part of the price of having JBL do the job. I'd strongly caution you against trying to break the magnetic pot apart on your own. You are likely to demagnetize the core and worse, hurt yourself at the same time. While it's true the structure is held together mostly by magnetic force , that force is strong enough to crush the ends of a finger ( or much worse according to my reconer ) when you try to pry that top plate off ( you're really playing with fire here ).
Leave this size job to pro reconers ( preferrably someone over 50 who's done this enough to know the risks - there are a few oldtimers who might do this job - they'll likely advise that a remag is order after their work is done )

regards <. Earl K

05-01-2003, 07:06 PM
Earl,I wasnt really going to use a hammer,I'm going to use a press to pull the top plate off ,at the same time freeze the magnet,this is the same method I used to repair the 075 and I did a few test tones against a sealed 075 and the output was the same on both units,I cant see sending the unit out @ a cost of $300 when I can pick up a used replacement for $250,too bad its so heavy or I would use it as a paper weight,worst case, damn good door stop!

Mr. Widget
05-01-2003, 07:28 PM
The 375/2440/376/2441 is held together by it's magnetic force. To replace the throat you must first demagnetize then after the work is complete, it must be remagnetized.

When I had it done a couple of years ago the whole rebuild including a new $200 diaphragm was about $350. This included cleaning and checking the gap, new gaskets, screws, a complete rebuild.

05-01-2003, 07:58 PM
I contacted my local pro shop for a similar repair. They couldn't do it themselves but referred me to Orange County Speaker. This is where they send their own drivers for repair. Here is there web site http://www.speakerrepair.com/ocsrepairprice.html
According to both shops the original throats are difficult to obtain, and my local shope told me that they can no longer obtain 2441 diaphragms from Northridge, so buy them while you can. Jammin Jersey is still advertising them for $150. Mike Caldwell at vintageaudiosales.com has clean used 2440 domes for $150 as well.

The procedure for replacing the throat involves degaussing the driver, replacing the throat, reassembling and regaussing. The cost for this was $65. The cost for realigning the phase plug, which apparently uses a special press and shims, was $35. A large cost is going to be shipping. Orange County is a JBL authorized repair shop and the quote is a lot less than JBL's quote.


Mr. Widget
05-02-2003, 12:49 AM
"and my local shope told me that they can no longer obtain 2441 diaphragms from Northridge"

Can anyone else confirm this. I bought a pair of new 2441 diaphragms from JBL within the last six months.
Are they now officially on the endangered species list?

05-02-2003, 06:30 AM
Well, these diaphragms go in and out of retirement depending on how big back orders get. Some diaphragms that are permenently gone are 066, 2480, 2416, 2420.

BTW, I can still get very good prices on brand new D16R2441's, D16R2421's, and D8R2425's and they are all currently in stock.

Mike Caldwell
05-02-2003, 07:19 PM
I just called the JBL service department about a week ago
to get prices on some 2440 throat repairs and they told me
$45.00. I was surprised at such a low price, with shipping it would be up to about $70.00 per driver. This price did not include
any replacement diaphragms, already have those!
Now just to get them packed and sent off!

Mike Caldwell

05-03-2003, 04:52 AM
Mike,Thanks for the info,I'll give Dave a call on monday,at that price I'll have them do it,I also have extra diaphragms,so I guess the price I got was with a new diaphragm,I will also see if I can send them the throat I already have,it is for a 375,I would think the 375 uses the same throat as the 2440?yes-no?

Mike Caldwell
05-03-2003, 08:09 AM
The throat is the same in all of that series of drivers, 375,2440,2441 and 2482.

I may be posting my broken 2440's for sale on the marketplace forum.

Mike Caldwell

05-03-2003, 08:50 AM
If throat is broken then the magnet is out of alignment also pry reason for shift is regaussing is pry needed. The troats are avalible from jbl for around 4.00 each as well as all need gaskets screws ect. I would send them to JBL and have the magnets regaussed and send back completely like new without diaphrams installed. Last time I checked it was around 40.00 a driver to have done. Only Way to go. When the magnet looses power then it tends to slip cracking out the throat. Call jbl service there is a special dock to shipp the drivers to to bypass the service dept. Ill look for the exact address.:D

Mr. Widget
05-03-2003, 11:30 AM
I just dredged up my invoice from JBL for having a pair of 2441s rebuilt 5/03/01

Replace gasket, part# 20810 $2.90
Replace throat, part# 21251 $8.50
Replace pad dampner, part# 60389 $6.70
Replace screws, part# 52602 $1.20

Labor Demag, remag $84.00
Labor remove rust from gap $42.00

This was done times two for a pair plus I had the diaphragms replaced at an additional charge of $392 for the pair.

Shipping and handling from LA to SF was an additional $16.50.

05-04-2003, 08:59 AM
Thanks for all the great info,I found another pair of 375 that are missing the diapragms and the covers,I checked the throats and the voice coil gaps and they seem to be in good shape,so I'm going to use the parts from the other set that has problems .

05-05-2003, 06:29 AM
Opening these up is no big deal really. Open cover, take diaphram, you will have to get something under the silver disc evenly around then just pry the disc out. The phase plug is held into place by the magnetic field. Realignment is not that difficult to get it close as you will see. Another thing that suprised me was how heavy the actual magnets are on the 30lb drivers pry about 4 lbs the rest is Structure/Housing. I recived 4 of these drivers free because of the cracked throats completely repaired them for about 50.00 all 4. Like I said all parts are available with no problems at all. Low magnetic feild will cause lower then normal output and if the magnet is not centerd properly there will be distortion. If you want to use them for critical monitoring id send them to JBL for overhaul, Be brave first and try the realignment first.