4430 with reconed E140's and 2425J drivers. Can it be done??

[Dutchman]

Hi, I'm new here and have a few questions. A couple of years ago I have fallen for the JBL 4430. In the Netherlands these speakers are very hard to find and being a student with a low budget makes things even more complicated . However last year I have been able to collect several parts I want to use to build these beauties myself (with some help of you fine people of course!). I've got the following parts:

2x JBL 2344a
2x JBL 2426J
2x JBL E140-8
Clone of the N3134 network (not yet build)

First question:
The JBL E140-8 will be reconed to a hybrid with 2235h reconekit. This will be done by a Dutch reconecompany. Should there be taken any precautions (flux-ring??) or can the reconekit be installed without any further adjustments?

Second question:
The 4430 uses 8 ohm drivers while I was hoping to use 16 ohm 2426J drivers. Can this be done and what adjustments must be made to the network in order to get the right (4430) sound?

Hopefully there's somebody who can provide me some answers. Thank you!!

[Zilch]

E140's will recone to 2235H nicely, with the JBL kit, of course. I'm doing a pair of these here myself next week. In theory, due to the higher magnetic force in the gap, the sonic character will be a little different, but not appreciably (or even audibly, very likely) so.

I wouldn't mess with trying to use 16-Ohm 2426's with N3134. It's just too precisely balanced for that 8-Ohm driver, and simple tricks like putting a 16-Ohm resistor across the driver are not going to work. Been there, done that. Replace the diaphragms with new 8-Ohm versions and recover some of the cost by selling the "used" ones as replacements.

I assume you've found the "Quick and Dirty 4430's" and the N3134 crossover construction threads....

[Dutchman]

Thank you Zilch!

I'm very glad to know that reconing the E140s to "2235h's" will work.


I've just removed the 16 ohm diaphragma's from the drivers and was wondering if you can tell from the diaphragma what it's impedance is. The diaphragma's do have several numbers on them but I can't find the codes 2425J/H 2426J/H anywhere. Is there a trick perhaps to find out?

[Dutchman]

Indeed Zilch "Quick and Dirty 4430's"

Few pics of the diaphragma's attached

[edgewound]

Dutchman:

Nice pics of diaphragms . The terminal with the red coloring signifies a 16 ohm diaphragm. An 8 ohm diaphragm will have a green coloring.

The frame and magnet assemblies for the E140 and 2235H are identical. The differences in performance are determined by the cone kit installed. Since these two models are in the interchangability list, you're going to be in great shape after the recone.

Thanks,
Edgewound

[Mr. Widget]

The frame and magnet assemblies for the E140 and 2235H are identical.

Mr. Edge . They are very similar, but they are not the same. The E130/E140 frame has a more massive magnet. It does change the TS parameters when a 2235 kit is put into an E series frame. (I have had it done.) The E series has a magnet that is 0.125" thicker and it's motor is rated at 13,500 gauss compared to the 2235H at 12,000 gauss.

Widget

2235E Blue
2235H Red

[scott fitlin]

Oopps!

[GordonW]

Mr. Edge . They are very similar, but they are not the same. The E130/E140 frame has a more massive magnet. It does change the TS parameters when a 2235 kit is put into an E series frame. (I have had it done.) The E series has a magnet that is 0.125" thicker and it's motor is rated at 13,500 gauss compared to the 2235H at 12,000 gauss.

Widget

2235E Blue
2235H Red

This is true... but, if one wanted to duplicate the factory response of a 2235H with the 2235H kit in a E140 frame, it's not hard to do. I modelled the parameters, and basically, all one would need, is to add about 16 grams of mass (roughly half the weight of a 2235 mass ring, IIRC) to the moving mass of the 2235. In the same box, this will result in a driver with exactly the same broad-band efficiency as the stock 2235H, and with the same general rolloff curves on the bass (same sensitivity at 20 Hz, for example) as a stock 2235. Yes, it'll be a tiny bit different in the midbass... but probably not enough to not be totally swamped by a slight change in room position of the speaker. IOW, probably not even enough to be readily audible as different from stock. In any case, these differencese in midbass could be easily overcome, with a slight change in port tuning... this would reshape the midbass readily, if necessary. Most likely, a very slight shortening of the factory port (as in maybe 1/2" or 1" shorter) would be maximum of what would be required.

IIRC, JBL is now shipping 2235H recone kits with a 4 3/8" dustcap, as opposed to the previous 4 1/8" dustcap... given this, there should be enough room to add 16 grams of a non-ferrous material (lead, as in short strips of solder, would suffice well), under the dustcap, around and on the factory mass ring. Just measure out 16 grams of the lead solder, and glue it onto the assembly as described, just making SURE that you DON'T make a complete circle around the cone/coil/mass ring (ie, you DO NOT want a "completed circuit" for induced electromagnetic energy to "short out" the motor magnetism... this would affect the effective field geometry and the effective magnetic strength, and is to be avoided at all cost). Just leaving a 1/4" space between the ends of the solder pieces, will suffice nicely. Once this is done, glue on the dustcap as normal. Given that the additional mass is concentrated around the voice coil, it should not affect the upper-end breakup behaviour (and hence, the upper end frequency response of the woofer) significantly... you should be able to use the woofer with factory crossovers, without problems...

For those who doubt this approach, I've actually DONE this with several woofers of various kinds and sorts, to 'fine tune' their parameters. If the mass is distributed as described, it will work...

Regards,
Gordon.

[edgewound]

Thank you for the back-up, Gordon . I'm not so sure the graphs are going to make a signifcant difference here....but I stand corrected. Looks like the E140 frame with 2235H kit is a better hot rod.


Edgewound

[edgewound]

Mr. Edge . They are very similar, but they are not the same. The E130/E140 frame has a more massive magnet. It does change the TS parameters when a 2235 kit is put into an E series frame. (I have had it done.) The E series has a magnet that is 0.125" thicker and it's motor is rated at 13,500 gauss compared to the 2235H at 12,000 gauss.

Widget

2235E Blue
2235H Red

I'm going to respectfully decline my being corrected.

Mr. Widget ....I just got off the phone with Dave at JBL Pro Tech Support...and we discussed magnet weight. Both the E140 and 2235H magnet assemblies(or motors) have the same published weight of 8.5 kg (18 5/8 lbs.) From a production standpoint, for all intents and purposes, the magnets of these drivers are identical...and there is no published weight for JUST the magnet disc itself. There might have been a variance of magnets from the supplier(s) that fell within acceptable limits and that explains the size differences in the magnets that you measured. Yes, the published flux densities are as you stated, but Dave tells me the magnets are the same for all the interchangable drivers/cone assemblies. The magnetic gap depth for the E140 and 2235H are both .28" and the magnet assemblies are the same weight and both have .057" gap width. Going by these numbers, how can the flux densities be different. Did you use a Gauss meter on your two units? The net weight for E140 & 2235H is both 22 1/4 lbs. What's up here?

Thanks for your indulgence,

Edgewound

[Robh3606]

Are the top plates the same thickness??


Rob

[edgewound]

Are the top plates the same thickness??


Rob

Yes...hence the .28" gap depth. I believe we had a similar discussion a while back with the 2440 vs.2441 measuring physically the same yet with different published flux densities. What'cha think....same obfuscating confusion? . I think we're splitting hairs here...the original post was about reconing an E140 to a 2235H...and the answer is a resounding YES!!! . Go for it Dutchman !!!

Edgewound

[Lancer]

The E130 and E140 had a 0.875" thick ferrite donut. The 2235H had a 0.75" thick ferrite donut. The flux densities were higher with the E130 and E140 magnetic assemblies. An E130 or E140 reconed with a 2235H kit would yield a hybrid driver with a 1 to 2 dB upward tilt in response across the entire bandwidth; greater sensitivity and a reduction in VLF output.

For use in a 4430 one would most likely need to tweek the 3134 crossover network to compensate. This hybrid transducer could probably be considered as something in between a stock 2234H and a stock 2235H. Note the differences in the 3134 and 3135 networks with respect to the two different transducers.

[edgewound]

My education continues...

Thank you, Gentlemen

Edgewound

[Lancer]

I think we're splitting hairs here

Possibly.

Many E130's and E140's have been reconed with 2225H and 2235H kits resulting in hybrid transducers. Depending on application, some people can hear a difference and some people can't. As one senior JBL transducer engineer stated once "The 2235H cone assembly in the E140 basket results in a more powerful 2235H, a bit less bottom end, a bit more top end.".

Note that a 2235H recone kit in a K130 or K140 basket will result in the same performance as a 2235H recone kit in a 136A or 2231A basket.

Some people prefer the sound of a K130 or K140 as compared to an E130 or E140.