4430 l-pads

[Ian Mackenzie]

Better check they are genuine JBL parts also.

They are not cheap are they. I remember when I bought my 2425's the kits they were $200 each.

While you have them open I would verify everthing is working in A1 condition. I assume you bought them from a trader so a check up is a good idea particularly given the age of the system, even the Pads. That's the down side of dabbling with all these older monitors and probably why some are less than satisfied about about the sound of their 70's vintage systems.

Its like buying a T model Ford with the original tyres, if its mechanical it can and will wear out eventually. Get it reconditoned and it will run as good as new.

Regards the polarity, I would think black is electrical negative by convention. Assuming identical pairs inside and out symmetry of wiring in each driver should be maintained.

I would not worry too much about the back covers, that may just be a different manufacturing batch.

Figge, for more specific information on this monitor you need to get expert advise on the drivers and someone with hands on experience with the 4430, I am sure plenty of 4430 owners with the 2421 drivers on the Forums have been here and seen this before.

You could Pm John Nebel our site sponsor. John's got most the better JBL monitors including the 4430, 4435. I was very impressed with the way John's JBL 4435's performed when I heard them so I am sure he will put you on the right track.


Ian

[Figge]

genuine jbl: i took the pic:s so the little numbers and letters on the coils are shown. thinking some of our experts here can tell a little what they are.

as for the price: i can buy used 2425:s or 26:s for less money than the new diaphragms. crazy price!

phase: well if its infact wrongly wired this most sertainly would affect the sound making exessive treble right?
i assume both driver diaphragms should be wired the same way. but must know for shure what the black mark is for.

authorized JBL: well i called them and asked about new diaphragms he said these "old" 2421 has a diaphragm that dont fit into the 2425, and the other way around. and he didnt seem to have heard about aluminium and titanium eather.

now giskard posted somewhere that the diaphragms are changeble between the 2421,2425 and 2426 cores. i do ceartainly trust giskard on this one. so i dunno how good/reliable answers i can get from them!

really need some serious help on this!

[John Nebel]

The 2421's should probably be remagnetized if you are replacing the diaphrams.

Why not test it again, making sure that the wires with the black trace are on the black speaker terminals? Check the 2235s too.

I've been using 2426s and bought those new. They sound fine.

John

[Figge]

well the wires from the crossover to the drivers were right!
but inside the 2421 it was diffrent between the two spakers.


so 2421 = alnico and 2425/26 = ferrite?

[John Nebel]

Originally posted by Figge

so 2421 = alnico and 2425/26 = ferrite?

Yes, the older is alnico and newer ferrite. If replacement is cheaper, why not do that? It would eliminate guessing.

The JBL specs and Giskard both say the crossovers were unchanged through the driver changes.

You might check the power handling specs on the older vs newer drivers if you want to play the systems loudly - the capacity was increased.

John

PS one might suspect that the drivers were f**ked with because one was blown. That could indicate that both the diaphrams and magnets were affected.

[Figge]

Originally posted by John Nebel
If replacement is cheaper, why not do that? It would eliminate guessing.

im thinking about it! and then sell my 2421:s maybe ít evens up so i didnt spend a dime?

BUT! the black mark on the diaphragm (the right screw in the pic below)
wich cable goes there red or black?

one of the drivers had black wire on the marking and the other one had red wire there!. shouldnt they be wired the same way?

this seem strange to me! someone obviosly has been fiddling around in there!

[4313B]

"so 2421 = alnico and 2425/26 = ferrite?"

The alnico 2421A core running the aluminum D8R2421 diaphragm was the original driver for the 4430/4435. JBL switched to the ferrite 2425H core running the titanium D8R2425 diaphragm in subsequent runs. Final versions used the ferrite 2426H core running the titanium D8R2425 diaphragm.

The alnico 2421B core running the aluminum D16R2421 diaphragm was the original driver for the 4345. JBL switched to the ferrite 2425J core running the titanium D16R2425 diaphragm in subsequent runs.

The diaphragms/cores are interchangeble. The difference between the alnico LE85/2420 core and the alnico 2421 core is supposed to be that the LE85/2420 core runs the aluminum DxR2420 diaphragm without the diamond pattern surround. The actual cores are supposed to be the same, only the foilcals and diaphragms are different between the LE85, 2420, and 2421.

*****

"BUT! the black mark on the diaphragm (the right screw in the pic below) wich cable goes there red or black?

one of the drivers had black wire on the marking and the other one had red wire there!. shouldnt they be wired the same way?"

Hook the wires up so the diaphragm moves out towards you (away from the phasing plug) when you apply a 1.5V battery to the terminals. + terminal on battery to red post on core. If you have a hard time seeing the movement put something across the diaphragm mount to better see the change in distance.

Since you have two different back covers check their volumes to see if they are the same.

[Figge]

ok! finished with the battery!

it appears in this case the black marking was + (red wire).
now when i put positive signal on it it pops up(away from the 2344).

gonna listen to it later on...neighbors are home

and the two diffrent backcovers seem to have the same volume.

im gonna check into changing them for 2425:s or 26:s. but they must be "H" right? J is 16ohm?

oh! and thanx all!

[Mr. Widget]

Here's my 2 cents worth on this.

My guess is that these diaphragms are indeed fatigued. The likelihood of them needing to be remaged is not high but if convenient it wouldn't be a bad idea.

Replacing the drivers with newer used titanium ones would be the least expensive option especially if you sold your alnico 2421As. I imagine a pair of 2426s would give you slightly more top end than perfect 2421As.

It seems that either one of your drivers was replaced or these 4430s were not siblings. What are the serial numbers of the 4430s? If they match then someone replaced a driver.

Personally, if they were mine, I would get the new JBL 2421A diaphragms and stay with the original aluminum diaphragms. While the aluminum does wear out faster than titanium, it is smoother sounding when good and will certainly last longer than you keep these speakers in a home environment. (Sure you will listen to these until you die they are that good... we have all said that before... realistically in a home environment the fatigue issue is almost nonexistent as long as you aren't blasting your neighbors on a daily basis.) These original drivers were not replaced because the newer drivers were better... the 2425 and subsequent 2426 were significantly less expensive for JBL to make!

Ok, maybe that was 4 cents worth.

Widget

[Figge]

Originally posted by Mr. Widget
What are the serial numbers of the 4430s?

255273 and 255530. any ideas what year that is?

[Mr. Widget]

Nope, but that seems far enough apart that they are probably outfitted with their original components.

Based on the 2421As they must be from the first year or two of production. Giskard has posted a matrix of the different monitors and the years they were in production. Doing a quick search I couldn't find it though.

Widget

[Figge]

this one?

[4313B]

"These original drivers were not replaced because the newer drivers were better... the 2425 and subsequent 2426 were significantly less expensive for JBL to make!"

Depends on your point of view. From a manufacturing perspective the titanium diaphragms offered substantially improved reliability. They also offered slightly increased high frequency response. In Pro applications the titanium diaphragms were unquestionably superior. The old aluminum diaphragms would shatter against the phasing plug. For home use, for which these systems were never intended, the increased damping of the aluminum diaphragms is generally preferred.

"and the two diffrent backcovers seem to have the same volume"

I figured as much but it's nice to be certain.

"ok! finished with the battery!"

You checked both drivers?

[Mr. Widget]

Originally posted by Giskard
"These original drivers were not replaced because the newer drivers were better... the 2425 and subsequent 2426 were significantly less expensive for JBL to make!"

Depends on your point of view. From a manufacturing perspective the titanium diaphragms offered substantially improved reliability. They also offered slightly increased high frequency response. In Pro applications the titanium diaphragms were unquestionably superior. The old aluminum diaphragms would shatter against the phasing plug.

Hey, I'm not dumping on JBL, but for critical listening in a studio or home environment it is my opinion and that shared by many others that aluminum diaphragms sound better as well as measure better in the area of distortion. I agree that the titanium diaphragms do have a bit more top end and to some that might be the tipping point.

Ultimately it's all personal preference... I am on a Beryllium kick these days myself.

Widget

[4313B]

I didn't think we were debating the fact that aluminum sounded better. I was trying to get across why JBL went with titanium. There is a very specific reason that has nothing to do with personal preference.