Jbl 3107

[Vahe Sahakian]

I have a DIY 4350 with original drivers. Have a question regarding the passive crossover 3107 which is what I have in the box.
The 2" midrange compression driver in its original setting sounds a bit too aggressive, too overpowering, and I am wondering if anyone has done any modifications to attenuate the output of this driver.
I am trying to find someone who is familiar with 4350's and can do the modifications for me.
Any other suggestions or recommendations would be appreciated.

Vahe
Houston, Texas

[speakerdave]

It may be that the "modification" has already been done. That is to say, if the original 2440 diaphragm has been replaced with either the aluminum or titanium diamond surround diaphragm, that crossover will not work. There is no low pass filtering on the high end of the pass band for the horn, since the 2440 diaphragm crashes at about 9k all by itself. I would check that first. If the 2441 was used instead of the 2440--it is more common, I think--that is likely the problem.

If the original diaphragms are still there, there may be some aging effects in crossover capacitors.

[Mr. Widget]

It may be that the "modification" has already been done. That is to say, if the original 2440 diaphragm has been replaced with either the aluminum or titanium diamond surround diaphragm, that crossover will not work. There is no low pass filtering on the high end of the pass band for the horn, since the 2440 diaphragm crashes at about 9k all by itself. I would check that first. If the 2441 was used instead of the 2440--it is much more common--that is likely the problem.

If the original diaphragms are still there, there may be some aging effects in crossover capacitors.Both very good points.

First, I would open up the 2440s and se what is in there... if you see a dark dull silver with a diamond surround they are likely 2445 diaphragms... I'd change those, if they are bright silver with diamond surrounds they are 2441s which is great, but incorrect for those networks, and likely tired anyway. If they have the older style half roll surround then they are original 2440 diaphragms, and are very likely tired and need replacing.

Alternatively, could be the sound of a properly working 4350 is more in your face than you prefer.

I would consider selling those 3107 networks and build a pair of 3155s. These are the updated networks that were developed for the 4355 and were designed to work with the 2441. They have separate controls for both the 2441 and 2405. I believe the schematics for an improved charge coupled version developed by member 4313B has been posted somewhere on the forum.


Widget

[Vahe Sahakian]

I have 2440’s in the system, they are in a perfect shape. It is the native “in your face” sound of the 4350’s that I am hoping to modify.
The 3107’s are about 20 years old, a couple of years ago I had our local JBL outfit service the units.
I do not have the know how to tackle electronics, do you folks know anyone that can build me the 3155 crossovers?


Vahe

[Mr. Widget]

I have 2440’s in the system, they are in a perfect shape. Have the diaphragms been replaced? If not, I doubt they are perfect.


I do not have the know how to tackle electronics, do you folks know anyone that can build me the 3155 crossovers?Assuming you do have perfect 2440s, you'll need to replace them if you go the 3155 route... it is designed to work with 2441s.

As for hiring someone... place an ad in the Marketplace area and see if someone responds. There are at least a couple of people who have taken 4313B's designs and built and sold them... I assume someone will do it for you, perhaps the master himself, if he has time.


Widget

[Vahe Sahakian]

I am learning so help me with info on 2440’s.

I will check the condition of 2440, being my first encounter I hope that I can identify the “tired” part if I see it.

The next question, is replacing these parts a DIY job or it needs to be done by a qualified tech? Also are these parts readily available and if they where can I obtain them?

Again appreciate all your help.

Vahe

[Mr. Widget]

I will check the condition of 2440, being my first encounter I hope that I can identify the “tired” part if I see it. No. You need sophisticated measurement tools and knowledge to be certain that a diaphragm is tired... a pair of good ears and a pair of drivers for comparison can also work.


The next question, is replacing these parts a DIY job or it needs to be done by a qualified tech?It can be done by anyone. Since it is easy to screw it up, the replacement diaphragms are quite expensive, and they are only covered under warranty if installed by a JBL certified tech... I'd go with the pro.


Also are these parts readily available and if they where can I obtain them?You can get them from numerous places, Orange County Speaker Service (http://www.speakerrepair.com/mm5/merchant.mvc?Screen=PROD&Store_Code=genem&Product_Code=10-255&Category_Code=JBL-Diaphragms) is one place.

I guess the bigger question is, what direction do you want to go? Do you want to invest significantly more money into these speakers just to see if they are what you want? I think I would be looking at other speakers... it is possible that getting new 2441 diaphragms and new 3155 networks will do the trick and you will be in audio nirvana, but it is also quite likely you could drop another grand into this project and still find the speakers not quite to your liking.


Widget

[Vahe Sahakian]

it is possible that getting new 2441 diaphragms and new 3155 networks will do the trick and you will be in audio nirvana, but it is also quite likely you could drop another grand into this project and still find the speakers not quite to your liking.


Let me understand your recommendation; I currently have 2440’s in my speakers, can these be fitted with 2441 diaphragms or I need to find 2441 to use wit 3155 networks?

I checked the frequency response curves of these two compression drivers, they are different, but I do not see much difference in the 1.1kH to 9kH region where they are used in the big JBL, am I missing something?

As for finding 3155 networks I will place an ad and see what happens.

The 4350’s, I am keeping, even if I end up spending another grand, there are not many speakers out there than can reproduce the huge dynamic range of well recorded material like these old JBL’s.

Again, thanks for your help, do not laugh I need all the help that I can get.

Vahe

[Mr. Widget]

I need all the help that I can get.I think you should spend some time reading these forums. All of your questions are answered, you will learn a ton and hopefully enjoy the process. :)

The 2440 and 2441 are the same driver. The difference is the diaphragm.


Widget

[4313B]

I think saeman tried some 2441's in a pair of 4350's and found them way too hot as would be expected. Or maybe it was some 3107's in a pair of 4355's, same difference. You'd have to ask him though.

Having personally run across a few partially discharged 2440 and 2441 cores I would recommend that one have them recharged at a place such as Great Plains Audio before putting fresh JBL diaphragms in them.

I've done a bunch of charge coupled 3107's and 3155's and sent them to Japan for evaluation and the response has been extremely positive. They have the means to dedicate extended A/B comparisons with a large group of unbiased listeners and the consensus is exactly as Greg Timbers predicted. Outstanding! They really had no clue what they were in store for and were completely floored at what fresh recones and charge coupled networks could do for these thirty plus year old systems. Now I just can't make enough of them. I'm actually finishing up three pairs of charge coupled 3155's this week before switching over to 3145's for awhile. In fact, every minute I waste on this forum is a minute far better spent making networks.

[Vahe Sahakian]

Now I just can't make enough of them. I'm actually finishing up three pairs of charge coupled 3155's this week before switching over to 3145's for awhile. In fact, every minute I waste on this forum is a minute far better spent making networks.

I need a pair of 3155's, can you help?

Vahe