Refresh your Vintage Compression Drivers

[Don McRitchie]

Giskard

Do you know the background of the 124A? I assume it was developed for the 4315, but I don't recall any consumer system that ever used it. I have only ever seen it as an LCS driver. For this reason, I assume they are quite rare.

[4313B]

Originally posted by Don McRitchie
Giskard

Do you know the background of the 124A? I assume it was developed for the 4315, but I don't recall any consumer system that ever used it. I have only ever seen it as an LCS driver. For this reason, I assume they are quite rare.

Hi Don,

It was the consumer version of the 2203 used in the 4315. It was part of the LCS line and a component in the S21 system. The EN3 enclosure was designed for the S21 system and could be purchased separately. The 121A used in the B212 was the same driver but had a heavier mass ring to create an even heavier moving assembly. The 2202 and 2204 used the same basket and magnetic assembly but had lighter moving assemblies. The 124A and 124H are quite rare.

[boputnam]

Originally posted by Giskard
The 124A and 124H are quite rare.

And will henceforth, be priced accordingly! Ha!

[GordonW]

Originally posted by Giskard
K
What should we push next week

Ooh! Ooh! LE-10As and PR10s!! LE10s and PR10s!!

Regards,
Gordon.
blatant shill-fishing...

[Don McRitchie]

For Don: This morning, thinking more about Alnico´s degradation, I guess just having a bar sitting there won´t affect it in 100 years, but with the magnetic poles almost shorted, except for the gap, Wouldn't it degrade sooner?

To my knowledge, it makes no difference. As the JBL rep indicated, there has to be a break in the magnetic circuit to cause it to demagnetize. One of the magnet company sites I came across stated that that care had to be taken in shipping energized Alnico magnets to ensure that they do not touch. It was not the actual touching that created a problem, but rather the act of pulling them apart. This action was certain to cause a partial demagnetization of both magnets.

[Figge]

ok i changed my compression drivers in my 4430:s from 2421A with really old alu:s to newer 2425H:s with BRAND NEW ti:s wasnt relly expecting much of a change but.
HOLY COW!!! uncompareble!



before i had some anoying hars screechy sound going...and it increased as i turnd up the volume!

after i installed the 2425:s i started up my amp and got some music going....it was like a breez of fresh air blew thruogh the room!

[4313B]

Yeah, it's just a fact of life that they are going to wear out. One nice thing about the 4430 is the relatively low cost involved with maintaining the system.

If you're running Ti then the life of the diaphragms goes up dramatically. Some studios in the L.A. area routinely change out the diaphragms every couple of years, sooner if the engineers hear anything at all amiss.

[4313B]

Originally posted by Don C
I replaced the diaphrams in my 044TI drivers recently as well, as Giskard said, it was a big improvement. I attribute a lot of the change to the replacement of the foam rubber pad behind the dome. That pad seems to be made of a material similar to the foam woofer surrounds, and it rots the same way.

The newer replacement diaphragms also have CCA wire. The original diaphragms would degrade over time due to copper and aluminum not liking each other.

[Figge]

Originally posted by Giskard
One nice thing about the 4430 is the relatively low cost involved with maintaining the system.

one other is that the system simply ROCK´N ROLL!

the new diphragms changed the whole sound of the system. when i first got em going i couldnt believe my ears i just sat there staring at the speakers. unbelieveble!


i still look like this!

[paragon]

Ok Bo,

I believe it. My 24 years 2441 are only driven at home listening
levels. First i had a pair of 2390, changed after four years into 2397.
Now i bought a pair of 2390 in Ebay and compared to the 2397.
The 2390 sounds very bad.
I never heared this 20 years ago. May be the old dias.
The 2397 make it all smooth compared to the 2390.
Okay, have to buy new dias. But what sort of ?
And what is about cone drivers ?
Is there also a change when you fix new ones in the basket ?
If yes, you have to pay a lot of money to restore your drivers.

Regards
Eckhard

[Figge]

Originally posted by paragon
Okay, have to buy new dias. But what sort of ?

buy the original JBL.

And what is about cone drivers ?

i guess they were out eventually too! i have a 20 year old 2235H in one speaker and a brand new in the other.

now with the old dias i couldnt tell a diffrence but now. hell the old sound dead in comarence to the new!

[paragon]

Thanks Figge,

So, what dias do you will take ?
Alu or the newer titan ?
I put new (australian) aftermarket titans in a pair of 2410`s
and they are going up to 17 kHz (-3 dB).
But they sound not so good as the big 2441.
May be the reason are the small H91 horns and not the dias.
If the aludias fatigue even at low power levels, there is ! a change
in cone drivers also, must be the spider,must be the cloth surround and of course the polyurethan (?) surrounds and
i think must be the cone himself !!
If you have a bass driver which goes up to 1000 or 1200 Hz
you must hear a change to a restored new one.
Nothing will match at all with old bass drivers (tuning),
Because surrounds are to hard or to soft, whatever, you have to tune your enclosure new to get best results.
So you have to change all, not only the high frequency drivers dias.
What do you guys think about ??

Regards
Eckhard

[Figge]

well...

i had 2421A:s with aluminium diaphragms that probably were 20 years old. i bought new 2425H drivers with titaninium dias. and the change was more than obvious, frekin´marvelous!

but! i guess a new alu had sounded even sweeter!

so go and buy yourself new !JBL original alu for yer drivers. and i guess all will be fine. you wont believe the diffrence until u changed them!!

as for cones: im no expert but as giskard said:

Performance of mechanical transducers degrades until eventual failure. They tend to follow the laws of nature pretty much like everything else.

and my new 2235 is definently more "alive" then the old one. so i guess i have a recone coming my way.

I put new (australian) aftermarket titans in a pair of 2410`s

But they sound not so good as the big 2441.
May be the reason are the small H91 horns and not the dias

could be? or not...u never will know, until u get the "right" diaphragm for that driver.

after all its the diaphragms you´re listening too, not the driver or the horn.

[4343]

when i first got em going i couldnt believe my ears i just sat there staring at the speakers. unbelieveble!

I was just listening to my 26 year old 2420 and felt the same way!

I did change the dia about 20 years ago when it broke while taking it to a gig, (bought a used one from a SR bud for $20...) and yes these 2420's have seen a LOT of SR use, but never with the passive 3122's they came with, always active at 2.5k or above. I only use the 3122's for stereo playback duties, so these puppies still sound great! (I think the alu fatigue must be worse if the driver is run down to the rated XO point of the horn, especilly for SR use.)