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Baron030
11-04-2006, 10:41 AM
I am currently restoring my old 030 systems. So, I thought I would take the extra time to document a few things. The N2400 crossovers pictured below were purchased in 1973 for $23.00 each and have serial numbers of 37510 and 38634. Since, the L-Pads were in really bad shape, I decided I would open up the boxes and inspect everything. To open the boxes, the heads of 4 rivets were very carefully drilled off. This allowed the back covers to be removed. Upon inspection, I turned up a few surprises. First, I was surprised by just how small the coils were in size, with only 20 gauge wire. Second, the coils had a different part number, then what was described in N2400 circuit schematic. So, I have revised the N2400 schematic below to show the differences that I found. Also worth noting in the #38634 – N2400 crossover, the 5 ohms were 10 watt instead of the 11 watt size. The pictures below are of the #37510 – N2400 crossover, which has the larger 11 watt resistors. In testing the N2400 crossovers, the #10421 coils had inductance values of 1.057mH and 0.997mH and all of the #10296 caps had values that varied between 6.1uF and 6.2uF of capacitance. Considering that the caps are 36 year old, I am pleasantly surprised by how well they have held up.
Baron030 :)

Baron030
11-04-2006, 10:44 AM
Since, I am turning my old 030 system over to my nephew, who is not very knowledgeable when it comes to electronics. I decided to replace a lot of the components. This would keep the old 030 system fairly trouble free for a really long time. Part Express had all of the parts that I needed. Their 15-watt mono L-Pads are an exact replacement for the JBL originals. And I decided to upgrade the #10421 JBL coils with 1.0mH - 18 Gauge Laminated “I” Core Inductors. And even though the #10296 JBL caps were in really good shape, I opted to replace each of them with 2 – 3.0uF Solen caps and a 0.01uF Theta AudioCap. After completely overhauling one of the crossovers, I did a side by side comparison. The crossover with the new components did sound a lot better. The 075s sounded slightly cleaner with the bypassed Solens. But, the most dramatic improvement was with the D/E130s, particularly at higher volume levels. I really think that the #10421 JBL coils are saturating and creating some distortion. So, the larger “I” Cores are a real improvement. Finally, to reinstall the original back cover, I first drilled out the old rivets and then tapped the holes to accept 6-32 screws.
Baron030 :)

spkrman57
11-04-2006, 11:09 AM
There are a few vintage fans amongst us who still play with the vintage older 2-way systems.

Regards, Ron

Titanium Dome
11-04-2006, 01:53 PM
Great pictures, too. Right up my alley. :thmbsup:

scott fitlin
11-04-2006, 02:51 PM
Hey, thats really cool. Your nephew should indeed be very happy with his new JBL,s and quite grateful to have such a super uncle!

:applaud:

John
11-04-2006, 03:02 PM
Nice thread!:) Thanks for sharing.:applaud:

glen
11-07-2006, 03:01 PM
Very nice reveal indeed Baron!
Thanks a lot for the detailed info and great photos.

fecooper
04-15-2009, 01:43 PM
You inspired me to bid on and win a couple JBL N2400 crossovers on e-bay which I then took apart and replaced the capacitors and resistors (did not replace inductor) as you did and put them back together. I used "pop" rivets (worked great) instead of threading the box. My speaker system consists of D-130 woofers and LE20 tweeters. Everything sounds great. I made one small change to the crossovers - I used a 4 ohm (series resistor) and an 8 ohm (parallel resistor) instead of two fives. I wanted a little more volume to my tweeter. I don't believe the LE20s are as efficient as the 075s (which I hope to get someday). With the fader control, I have enough range to make the adjustment.

Thanks for the inspiration to jump in and modify a JBL crossover.

Baron030
04-15-2009, 03:53 PM
Well, I can see that this is your first posting here.
So, welcome to the LH forums.
I’m glad that I could be of some help around here.

Baron030:)

2turbos
08-01-2009, 08:26 AM
Since, I am turning my old 030 system over to my nephew, who is not very knowledgeable when it comes to electronics. I decided to replace a lot of the components. This would keep the old 030 system fairly trouble free for a really long time. Part Express had all of the parts that I needed. Their 15-watt mono L-Pads are an exact replacement for the JBL originals. And I decided to upgrade the #10421 JBL coils with 1.0mH - 18 Gauge Laminated “I” Core Inductors. And even though the #10296 JBL caps were in really good shape, I opted to replace each of them with 2 – 3.0uF Solen caps and a 0.01uF Theta AudioCap. After completely overhauling one of the crossovers, I did a side by side comparison. The crossover with the new components did sound a lot better. The 075s sounded slightly cleaner with the bypassed Solens. But, the most dramatic improvement was with the D/E130s, particularly at higher volume levels. I really think that the #10421 JBL coils are saturating and creating some distortion. So, the larger “I” Cores are a real improvement. Finally, to reinstall the original back cover, I first drilled out the old rivets and then tapped the holes to accept 6-32 screws.
Baron030 :)

I followed what you did and scratch built a set of these crossovers for my D-123/075 rehab of my Dad's 50's speaker system. His crossovers were 1st order and the Hf would distort as there was no adjustment pad for the 075. The 5 ohm resistor update might have been a big help.
Thanks for the thread Baron 030, it was a nice piece of research.

wmckee
02-12-2012, 07:45 PM
It appears from the photo of the upgrade of the N2400 crossover that the resister bridge is not wired per the the original JBL schematic. Granted, the pictures do not show everything, but it looks like the two 5 ohm resistors from the L-Pad <red wire> do not go to <black> and <capacitor-red> respectively, but are both twisted together and probably go to <capacitor-red> with nothing going to <black>. This would actually work and approximate the protective additional resistance that JBL wanted to use to protect the 075.

First, is my observation correct? Second, was this done on purpose and, if so, why?

Otherwise, a fantastic job of documenting this N2400 upgrade, which I am in the process of implementing myself.

Thanks, Walt

Baron030
02-13-2012, 08:26 AM
Hi Walt
The pictures may not look right to you. But, I can assure you that the networks were rebuilt correctly to JBL specs and that they follow the schematic that I posted perfectly. The purpose of the two 5 ohm resistors is to create a -8.5db, fixed L-PAD network. This limits the maximum setting of the variable L-PAD network to prevent damage to the 075 driver. I suspect that before JBL added the two 5 ohm resistors, they had service issues with careless 030 system users.

Baron030:)

Baron030
02-13-2012, 09:03 AM
Hi Walt

I just had a thought as to why you might think that the L-Pads pictured were not wired up correctly. In the re-build, I used 15 watt Dayton L-Pads. The Dayton L-Pads may have a different pin layout then the original JBL #10285 L-Pads. So, if you are going to use Dayton L-Pads, then follow their instructions and schematic that comes with their pads. Otherwise, you may not get them wired correctly in the network.

Baron030:)

wmckee
02-14-2012, 12:08 AM
Baron030,

The question was not about the L-Pad (I used the generic Parts-Express one), only the two 5 ohm resistor bridge itself and where the ends of the bridge connect to regarding the rest of the circuit. I am trying to attach a JPG showing what confused me. I was sure I had it wrong but still wanted to ask -- it just looked like the end-points of the bridge (unlike the schematic) were twisted together in the photo.

Walt

Baron030
02-14-2012, 08:55 AM
Hi Walt
The picture you posted has the coil covering a solder lug terminal. I magnified the pervious photo where the coil has not been installed yet. Now it’s hard to see but there are two resistors stacked on top of each other. I have highlighted the same wire that you are talking about with red arrows and the other connections are color coded in blue, green and cyan. And I have highlighted the same connection points on the schematic. I am not sure if this helps clears things up or not.
Baron030:)
5477654777

grumpy
02-14-2012, 11:26 AM
Dude...
pervious photo? wrong forum me thinks. ;)

Baron030
02-14-2012, 11:51 AM
Dough! :homer:

I know I make miss steaks in my last posting. It's all because I used special soft ware witch checks yore spelling. It is mower or lass a weigh too verify. However is cannot correct arrows inn punctuation ore usage: an it will not fined words which are miss used butt spelled rite. Four example; a paragraph could have mini flaws but wood bee past by the spell checker. And it won’t catch the sentence fragment which you. Their fore, the massage is that proofreading is not eliminated, it is still berry muck reek wired.

Baron 030 :blink:

wmckee
02-14-2012, 03:14 PM
Baron 030,

Thanks, that did clear everything up. I could not see the second resistor wire (blue arrow) in the photo -- it looked like a shadow of the wire indicated by the red arrow to me. Plus the wire indicated by the red arrow looked a little like a twisted pair. Thanks again for taking the time for such a detailed explanation.

Walt

grumpy
02-14-2012, 04:14 PM
good info... had to rib you at least a little. :D

spaceholder
01-08-2014, 12:15 AM
Hello everyone, I'm in the process of building these x-overs for a pair of 030s that I bought. I'm a bit of a newbie at reading schematics and am not sure I have gotten all the connections right. I have, by the way, I looked at all the pictures of other people's builds, and they have been a big help.

I'm hoping that Baron or anyone else familiar with these crossovers would look at my pictures and tell me if I am on the right track.

610916109261093.

I realize this is an old thread, but it seems to be becoming a useful resource these rebuilds, if mods think this should be a new thread just let me know.

Edit: I can't seem to figure out how to rotate the pics, anyone have a hint?

Baron030
01-08-2014, 09:00 AM
Hi
One picture can say a thousand words. So, I used Microsoft Paint modify one of your pics.
Hope this helps.

61095

Baron030:)

spaceholder
01-08-2014, 01:52 PM
Wow Baron, thanks so much. I have attempted to implement your fixes, would you have another look and tell me if I'm getting close? I have included a pic of the l-pad diagram, because in a bit confused by that as well. (have you noticed a theme here?)

611046110561106

61103

Also, I would like to order some "audiophile approved" hookup wire. I don't want to open a pandora's box (if possible), but I'm wondering about gauges and stranded vs solid. Does anyone have any advice?

Baron030
01-08-2014, 03:19 PM
61107
For speaker wire I use 12-gauge 2 conductor landscape lighting cable.
You can get about 100 feet of it for about $60.00.
So, it's not overly expensive.
Baron030:)

spaceholder
02-06-2014, 12:11 AM
Thank you Baron!
I've got the x-over working now and it sounds great, really a huge improvement. I'm going to swap some film caps in to see if things improve even more.