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View Full Version : Field Guide to the JBL 10 inch Midbass driver 2121 2122 2123



hjames
05-31-2007, 07:11 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.

hjames
05-31-2007, 07:13 PM
Thanks again to Subwoof for these amazing pictures!

The Voicecoil comparison
2121 on the Top
2122 in the Middle
2123 below

hjames
05-31-2007, 07:31 PM
Yet again, thanks to Subwoof for these pictures!

Comparison of the magnet structure

2121 beside the 2121H

2122H beside a picture of my 2123H driver (now in Maui)

(Sorry for the dissimilar style of the 2123 picture, but I know there is enough interest that it was worth including)

4313B
05-31-2007, 08:20 PM
Just a quick note that the LE10A in the photo is sporting the wrong dust cap (might even be an LE10H-1 recone kit in it).
It used the same dust cap as the 2121 next to it.

hjames
06-01-2007, 07:40 AM
Did JBL ever publish a response curve for the 2122H? I can't find it...


I posted it somewhere.

Right here, G -
and X_X - the forum search tool is your friend!
2122H - http://audioheritage.org/vbulletin/showthread.php?t=10637

Fangio
06-29-2009, 01:10 PM
early 2121 with lansaloy surround.

ivica
01-02-2011, 01:46 PM
Thanks again to Subwoof for these amazing pictures!

The Voicecoil comparison
2121 on the Top
2122 in the Middle
2123 below

Very instructive photos, difficult to find .
Do you have the same photos of the voice coil for E110 and K110.
It would be interesting to see the difference of the coils

1audiohack
01-02-2011, 03:28 PM
The voice coil and spider on the E110 looks just like the 2121 pictured, VC is 0.300" tall, the cone is only 0.014" thick. By comparison the 2123's VC is 0.440" tall and the cone is about 0.024" thick. I don't have a 2122 kit to look at.

hjames
01-02-2011, 03:48 PM
Thanks again to Subwoof for these amazing pictures!

The Voicecoil comparison
2121 on the Top
2122 in the Middle
2123 below
Very instructive photos, difficult to find .
Do you have the same photos of the voice coil for E110 and K110.
It would be interesting to see the difference of the coils

The Pix on the 10 inch series were primarily from Subwoof -

>> Thanks to Subwoof for these amazing pictures!

subwoof
01-02-2011, 05:25 PM
If I remember, the K110 and E110 had the same coils but the former changed a few times on the "E" which made for a slightly different spec.

I don't have any of those open or kits to compare at the moment BUT I think I have some pretty rare K110-4 kits in storage. When it thaws I will look.

sub

ivica
01-30-2011, 05:38 AM
The voice coil and spider on the E110 looks just like the 2121 pictured, VC is 0.300" tall, the cone is only 0.014" thick. By comparison the 2123's VC is 0.440" tall and the cone is about 0.024" thick. I don't have a 2122 kit to look at.

Thanks for info,

1.
so concerning the VC differences - thickness and length, are they all 8-ohms VC for three ( E110, 2121 2123), or 16 ohms
2.
do you have any experience about re-coning E110 basket with 2123 re-cone kit

1audiohack
01-30-2011, 08:16 AM
Yes, the last six I assembled were E110 baskets with C8R2123H kits.

To clarify, thickness I made reference to is the cone material of the radiating element, not the voice coil or former.

The dimensions of a 2123H coil and former are approximately 2.995" I.D., former and wire combined thickness 0.028" and wound coil height 0.440".

E110H about 2.995" I.D., former and coil combined thickness 0.022" and wound wire height 0.285"

Hope this helps.
Barry.

ivica
01-31-2011, 12:10 AM
Yes, the last six I assembled were E110 baskets with C8R2123H kits.

To clarify, thickness I made reference to is the cone material of the radiating element, not the voice coil or former.

The dimensions of a 2123H coil and former are approximately 2.995" I.D., former and wire combined thickness 0.028" and wound coil height 0.440".

E110H about 2.995" I.D., former and coil combined thickness 0.022" and wound wire height 0.285"

Hope this helps.
Barry.

Many, many thanks,

So I understand that I can put re-cone kit for 2123 without any modification into E110 basket.
Is there any large differences in the sound between E110 and 2123 (after re-conning)??

1audiohack
01-31-2011, 07:30 AM
The E110 / 2123 basket / motor assemblies are identical. A 2123 kit in a E110 basket will be a proper 2123, except for the foil cal.

All the best,
Barry.

grumpy
01-31-2011, 08:08 AM
...
Is there any large differences in the sound between E110 and 2123 (after re-conning)??

I would expect so, partly depending on how they are used; in a system or standalone:

http://www.audioheritage.org/vbulletin/showthread.php?29742-2123
http://www.audioheritage.org/vbulletin/showthread.php?10635-E110-8

ivica
02-14-2011, 06:53 AM
I would expect so, partly depending on how they are used; in a system or standalone:

http://www.audioheritage.org/vbulletin/showthread.php?29742-2123
http://www.audioheritage.org/vbulletin/showthread.php?10635-E110-8

Many thanks, so with overlaying responses of 2123 and E-110 I get the following.
That would be some helpful for network changes if E110 is used in to say 4343 or 4345

ivica
09-07-2011, 07:19 AM
Many thanks, so with overlaying responses of 2123 and E-110 I get the following.
That would be some helpful for network changes if E110 is used in to say 4343 or 4345
Added 2122 response.
But all of responses are so called 'small signal responses'. On higher power I do believe that they are
much different.
It would be nice if such measurements somebody can add.

EvilFuzz
06-07-2012, 07:15 AM
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.

Some idea: if I rewind 2123 coil with copper ribbon (with 2122 JBL specs), it will be 2122? Or cones paper and magnets is different too?
Thanks,
Kirill

ivica
11-01-2012, 08:16 AM
Some idea: if I rewind 2123 coil with copper ribbon (with 2122 JBL specs), it will be 2122? Or cones paper and magnets is different too?
Thanks,
Kirill

As I remembered 2122 is 'under-hung' (shorter voice coil that pole plate thickness),
while 2123 is 'over-hung' ( VC longer then pole plate thickness), and cone suspensions ( Vas) are different too. You can see in T/S parameters for 2122 and 2123.

Reagrads
Ivica

1audiohack
05-10-2016, 10:13 AM
Does anyone know if the LE10H basket/motor assembly is the same as a 2122-2122-2123 (tel:2122-2122-2123)? They sure look like they are based on the pictures I can find but none show a clear side shot.

I have never seen one. The goes into list doesn't lead me to believe they are the same but I don't know for sure when it comes to pro part numbers verses home stuff.

Any help would be greatly appreciated.

Thank you,
Barry.

4313B
05-10-2016, 10:30 AM
2121H = 2122H = 2123H = LE10H = LE111H
2121A = LE10A but neither equal LE111A which had a much larger AlNiCo structure resulting in an absurdly low Qts, extremely overdamped, but it actually sounded pretty nice in the original L110. :)

1audiohack
05-10-2016, 10:54 AM
Thank you very kindly!

Barry.

Flodstroem
05-12-2016, 11:48 AM
2121H = 2122H = 2123H = LE10H = LE111H
2121A = LE10A but neither equal LE111A which had a much larger AlNiCo structure resulting in an absurdly low Qts, extremely overdamped, but it actually sounded pretty nice in the original L110. :)

How do you guys compare the 2012H against the the 2121, 2122 and the 2123? Better or worse? And is there any benefit to use it in the monitors?

1audiohack
05-12-2016, 12:22 PM
I LOVE 2012's, and 2020's.

Barry.

Flodstroem
05-12-2016, 03:07 PM
I made a search of the entire forum and I found a lot of information about the 2012H compared to the other 10 inch midrange speakers
As an example, Guido has posted som interesting info about this 2012H speaker and the 4343 but I dont know if he ever used that driver in his monitors?
http://www.audioheritage.org/vbulletin/showthread.php?218-Inductance-of-2012H&highlight=inductance+of+2012H

Elac310
12-05-2016, 11:57 AM
Has anyone experience with using these over-engined and high Fs 10" drivers in satellites down to 100 hz ?

JBL has done this on the little 2 way box 4716A if I get it right. My idea is to then add a big subwoofer to end up with some sort of a triphonic system.

Ian Mackenzie
12-06-2016, 08:49 AM
This was discussed quite some time ago

As l recall the Xmas of the 2123 in a sealed enclosure for this application will be a limiting factor but you could port/vent the enclosure.


Plug the 2123 into a simulator and see if it will be viable?

The 2118 maybe a better candidate.

pos
12-06-2016, 09:57 AM
As l recall the Xmas of the 2123 in a sealed enclosure for this application will be a limiting factor:sleigh:

The 2012 could be a good condidate as it has a much higher xmax

bldozier
01-05-2017, 07:06 PM
Jbl thermometer, great thread. Ty.

FREDFLYPOGGER
03-14-2017, 10:34 PM
I LOVE 2012's, and 2020's.

Barry.

Hi Barry
I can't reply to your response you are out of space, need to clean up some emails. I am interested in the pair of 2121 cones
thanks
todd

Havana Woody
09-24-2019, 02:00 PM
I have had for 35+ years two E-110 and two M12-8 in .6 sf sealed boxes and they have been the best sounding mid range Piano speakers I have ever had. They have been in my attic awaiting re-coning for 10 years. and apparently that is about 12 years past the expiration of available factory kits. I can't find any references for the M12-8 (not M112) except one line in a resource I found here that shows them to use the same kit as the E-110s which makes sense because they are Identical baskets to the eye. Now I see that there may be a glimmer of hope I can get the C8R2123H kits. or equivalent. Can anyone point me to a reliable and quality source you have got these from Or perhaps someone has 4 they need to sell. I really miss the hard hitting snap these provide. I can't get that kind of energy out of my Kappa6 and the 10W1-8s I replaced them with after they started making noise Just never had the crisp sound that the paper surrounds did.
any help or suggestions would be welcome.

Havana Woody
09-24-2019, 02:08 PM
If I remember, the K110 and E110 had the same coils but the former changed a few times on the "E" which made for a slightly different spec.

I don't have any of those open or kits to compare at the moment BUT I think I have some pretty rare K110-4 kits in storage. When it thaws I will look.

sub

Are you still around ? I know my storage has some untouched areas that are over 8 years , hoping by long shot to find you still have these

1audiohack
09-24-2019, 03:47 PM
JBL still has C8R2123 kits.

Barry.

Havana Woody
09-25-2019, 06:51 AM
JBL still has C8R2123 kits.

Barry.
Thank you Barry !

I must not have ask the tech in the right manner, I suppose they might not make the leap to suggesting the 2123 when I was asking about the E-110, Maybe I wasn't in the right store, were does a average consumer go to best order parts from JBL?

Mr. Widget
09-25-2019, 08:38 PM
...Maybe I wasn't in the right store, were does a average consumer go to best order parts from JBL?You cannot buy JBL recone kits from legitimate JBL dealers/repair facilities that follow the rules. Your best bet is to work with a reputable factory authorized repair facility. They will correctly install the kits in your cores for you.


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