Infredible
New Member
Hello nice people!
I was on the Lansing Heritage many moons ago. I just subscribed again here on AudioKarma, feels like home.
One of my first post on the Lansing Heritage forum back then:
For about 25+ years I have in my possession a very nice pair of original JBL 4343 all alnico in a very good physical condition. I am currently using ferrite 2121's because my original Alnico's are in need of a complete recone, the paper is gone to mush.
With the help of Mr. Widget, we replaced the aluminium diaphragms back then with newer beryllium? ones courtesy Mr. Giskard. I have sadly since lost the originals aluminium in a house moving, they got crushed to death
I have reafoam the 15" and 10" several times since, always using MidWest Speaker repairs' foam kits. I will re-foam the ferrite 2121 this time. I use my speakers every single day to listen to my favorite playlists. I use Tidal, Qobuz and a Roon server. I use an R2R DAC to feed my single amp for now but I have an Ashly XR1001 and another big Hafler 2X300W on the shelf that is in need of new J-Fets for bi-amping the 4343's.
During my long listening hours, I have noticed some serious imbalance especially between my 2420's. The left sounds way harsher than the left and no measure of L-pad tweaking restores a somewhat linear response. I can compensate for it easily in Roon-MUSE but I don't like the idea that my nice high-res signal passes through some more than 70 years capacitors. I am sure they still hold some values but I really want to upgrade them by replacing the old technology with high quality ones available today.
I don't want to disassemble everything to pieces, I just want to open the boxes, cut the old stuff and resolder/attach the new stuff and secure the all thing against vibrations from the 15"s.
I know one of my 2040 l-pad is miserable, I may replace it to with a Part-Express 50W 16 ohm with a 1 inch shaft transplant from a 8 ohm L-pad. I don't know how difficult it is to replace the L-pad without destroying the beautiful front aluminium decal foil. I not planning on replacing the inductors for now, I'll measure them during upgrade for good measure... ah!
Now comes the mystery part...
After spending a really long time on the internet, on forums and using AI researches from Gemini, Chat GTP and Claude, none could return an ORIGINAL JBL 3143 CROSSOVER SCHEMATICS!
There's a couple of schematics versions floating around but they're either modified ones or handwritten on a piece of napkin. There's no conclusive response, none seem to be the the authentic original.
It it the main reason for my post, short on opening the speaker and extracting the crossover in order to figure out the written values that have probably faded by now. I just want a part list parts to place an order. Once I have the parts, I am going to dive into the box to do all the work at once.
I hope that somewhere a nice soul is listening and is willing to share this information with the me and the forum or in a PM. I would be SO greatful and also make a donation for this forum. I need to know the number of capacitor used in the circuit and their original values. Sounds simple...
I plan to spend around $100-150 just for caps which gives me a good window for good quality modern components. Any recommendation is welcome. Please! I don't want to trigger another discussion about capacitor technology, this has been beaten to death in other threads, I'm just looking for an answer.
Thanks peeps for reading me!
Fred.
I was on the Lansing Heritage many moons ago. I just subscribed again here on AudioKarma, feels like home.
One of my first post on the Lansing Heritage forum back then:
In or out?
My 4343 came with the 2405's on the right side on both speakers. What is the ideal placement for them? As is or mirrored and if so should they be placed inward or outward. What arrangement gives the best imaging? Thanks. Fred.
www.audioheritage.org
For about 25+ years I have in my possession a very nice pair of original JBL 4343 all alnico in a very good physical condition. I am currently using ferrite 2121's because my original Alnico's are in need of a complete recone, the paper is gone to mush.
With the help of Mr. Widget, we replaced the aluminium diaphragms back then with newer beryllium? ones courtesy Mr. Giskard. I have sadly since lost the originals aluminium in a house moving, they got crushed to death
I have reafoam the 15" and 10" several times since, always using MidWest Speaker repairs' foam kits. I will re-foam the ferrite 2121 this time. I use my speakers every single day to listen to my favorite playlists. I use Tidal, Qobuz and a Roon server. I use an R2R DAC to feed my single amp for now but I have an Ashly XR1001 and another big Hafler 2X300W on the shelf that is in need of new J-Fets for bi-amping the 4343's.
During my long listening hours, I have noticed some serious imbalance especially between my 2420's. The left sounds way harsher than the left and no measure of L-pad tweaking restores a somewhat linear response. I can compensate for it easily in Roon-MUSE but I don't like the idea that my nice high-res signal passes through some more than 70 years capacitors. I am sure they still hold some values but I really want to upgrade them by replacing the old technology with high quality ones available today.
I don't want to disassemble everything to pieces, I just want to open the boxes, cut the old stuff and resolder/attach the new stuff and secure the all thing against vibrations from the 15"s.
I know one of my 2040 l-pad is miserable, I may replace it to with a Part-Express 50W 16 ohm with a 1 inch shaft transplant from a 8 ohm L-pad. I don't know how difficult it is to replace the L-pad without destroying the beautiful front aluminium decal foil. I not planning on replacing the inductors for now, I'll measure them during upgrade for good measure... ah!
Now comes the mystery part...
After spending a really long time on the internet, on forums and using AI researches from Gemini, Chat GTP and Claude, none could return an ORIGINAL JBL 3143 CROSSOVER SCHEMATICS!
There's a couple of schematics versions floating around but they're either modified ones or handwritten on a piece of napkin. There's no conclusive response, none seem to be the the authentic original.
It it the main reason for my post, short on opening the speaker and extracting the crossover in order to figure out the written values that have probably faded by now. I just want a part list parts to place an order. Once I have the parts, I am going to dive into the box to do all the work at once.
I hope that somewhere a nice soul is listening and is willing to share this information with the me and the forum or in a PM. I would be SO greatful and also make a donation for this forum. I need to know the number of capacitor used in the circuit and their original values. Sounds simple...
I plan to spend around $100-150 just for caps which gives me a good window for good quality modern components. Any recommendation is welcome. Please! I don't want to trigger another discussion about capacitor technology, this has been beaten to death in other threads, I'm just looking for an answer.
Thanks peeps for reading me!
Fred.
