hjames
05-31-2007, 08:11 PM
One of the magical things about the 4340/41, 4343 and 4345 Monitors is the 10 inch Midbass driver. This driver helps the big woofer (15 or 18") handle just the really low notes, and keeps the horn/compression driver from having to go below its optimal range.
Here's a thread showing how Infredible redid the surrounds on a pair of those ultra-rare 2121s - http://audioheritage.org/vbulletin/showthread.php?t=3527 (http://audioheritage.org/vbulletin/showthread.php?t=3527)
In an older thread, (http://audioheritage.org/vbulletin/showpost.php?p=2177&postcount=11)Giskard said
The 4343 uses the alnico 2121 and the 4343B uses the SFG ferrite 2121H. Both have the 4" inverted paper dust cover.
The 4344 and 4345 use the newer 2122H which has a harder 3" dust cap. It is less susceptible to break-up.
All of them use a 3-inch edgewound copper ribbon voice coil.
*****
"Isn't this inconsistent with what we would normally use above 300Hz? I would assume aluminum would be desired due to the lightness and quick response at the higher frequencies."
Sure, it just wasn't in the cards way back then. The newer 2123H uses an aluminum voice coil.
Thanks for that info, G!
One thing thats a problem for modern fans is that the original model 2121 driver is unavailable. It was replaced by the model 2122 - which is rapidly getting near impossible to find as well. You can occasionally find a replacement cone (as of May 2007) for a rebuild, but even they are in quite short supply.
Some folks have substituted the model 2123 driver - but its not equivalent, its more efficient (higher output levels), and has a different response curve that the earlier 2 drivers. You'd need to re-design the crossover and, frankly, its just not the same driver.
But some folks do like it.
Thanks to Subwoof for these amazing pictures!
The Lineup up basic JBL 10 Inchs
At the bottom -
For those who can read the design specs - here's a chart Giskard has posted numerous time showing the different parameters.
Here's a thread showing how Infredible redid the surrounds on a pair of those ultra-rare 2121s - http://audioheritage.org/vbulletin/showthread.php?t=3527 (http://audioheritage.org/vbulletin/showthread.php?t=3527)
In an older thread, (http://audioheritage.org/vbulletin/showpost.php?p=2177&postcount=11)Giskard said
The 4343 uses the alnico 2121 and the 4343B uses the SFG ferrite 2121H. Both have the 4" inverted paper dust cover.
The 4344 and 4345 use the newer 2122H which has a harder 3" dust cap. It is less susceptible to break-up.
All of them use a 3-inch edgewound copper ribbon voice coil.
*****
"Isn't this inconsistent with what we would normally use above 300Hz? I would assume aluminum would be desired due to the lightness and quick response at the higher frequencies."
Sure, it just wasn't in the cards way back then. The newer 2123H uses an aluminum voice coil.
Thanks for that info, G!
One thing thats a problem for modern fans is that the original model 2121 driver is unavailable. It was replaced by the model 2122 - which is rapidly getting near impossible to find as well. You can occasionally find a replacement cone (as of May 2007) for a rebuild, but even they are in quite short supply.
Some folks have substituted the model 2123 driver - but its not equivalent, its more efficient (higher output levels), and has a different response curve that the earlier 2 drivers. You'd need to re-design the crossover and, frankly, its just not the same driver.
But some folks do like it.
Thanks to Subwoof for these amazing pictures!
The Lineup up basic JBL 10 Inchs
At the bottom -
For those who can read the design specs - here's a chart Giskard has posted numerous time showing the different parameters.