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JBL Dog
03-14-2011, 10:16 AM
I bought a vintage JBL pro PA over the weekend. Part of the haul was a few 2441 drivers. One of the 2441's has a hairline crack in the throat. I have not bench tested the driver yet. Am I dealing with a cosmetic issue or will there be performance problems? The crack does not circle the entire throat..... only about half of it.

Any opinions? Thanks!

:D
Audiobeer
03-14-2011, 11:05 AM
Bob you know i don't know shit about it but is the throat textured? Is it aluminum or steel?
JBL Dog
03-14-2011, 11:14 AM
Bob you know i don't know shit about it but is the throat textured? Is it aluminum or steel?

Actually, the throat is a hard plastic.
subwoof
03-14-2011, 11:20 AM
sigh...

the throat is bakelite and it cracks when the magnet gets weak enough that normal handling moves it or it was really dropped and both scenarios mean a loss of strength.

remag and live with the crack...BUT shipping this to a center will finish the crack so it's a dilemma.

sub
JBL Dog
03-14-2011, 01:07 PM
sigh...

the throat is bakelite and it cracks when the magnet gets weak enough that normal handling moves it or it was really dropped and both scenarios mean a loss of strength.

remag and live with the crack...BUT shipping this to a center will finish the crack so it's a dilemma.

sub

Thanks for the reply, sub.

So, what to do with it? Is there any value to a 2441 with a cracked throat? Other than the crack, it's in nice shape. I inspected the diaphragm and phase plug, no problems. DCR readings are within spec (8.1).

Would bench testing shed more light on it?

:hmm:
grumpy
03-14-2011, 01:40 PM
There's a thread here (somewhere) where a forum member is having an Aluminum
replacement version machined... I don't recall how that went, or if it was completed
successfully.
Mr. Widget
03-14-2011, 01:42 PM
A number of years ago I had a pair of 2441s shipped using our pals at UPS... they had been incased in molded in place foam. The box was dropped repeatedly and both drivers bounced around pummeling each other cracking the throats... barely visible, but cracked. I called JBL and at that time they still did in house repair at Northridge. The plastic throat was just a few bucks but the demag required to replace it and subsequent remag, assembly, and alignment wasn't trivial. Upon testing both, beautiful looking 2441 diaphragms failed the JBL QC and had to be replaced.

The bottom line is what do you want... something that plays music or a driver that meets it's original design spec? To make sure it is really right requires a complete rebuild and most likely a new diaphragm. I am sure this will cost more than what you currently have in the driver.

Widget
louped garouv
03-14-2011, 03:15 PM
There's a thread here (somewhere)

here it is!

http://www.audioheritage.org/vbulletin/showthread.php?29464-Refurbishing-a-pair-of-2440/page3&highlight=aluminum+throat


sounds like the gentleman is offering to provide the dimensions/cnc g-code for anyone wanting to reproduce his efforts (PM him directly) on a non-commercial basis too!


good luck whichever way you choose to go....
subwoof
03-14-2011, 06:08 PM
Well give it a sweep and make sure the diaphram / gap is ok before making any $$ decisions. There's a good chance that the *normal* variation between drivers is greater than any "loss".

If you have 4 of these, get a SPL level of each at 10K and match them up. If you are going to use a tweeter above them it won't matter much anyways.

sub