I am taking apart this 4312 set and want to refresh the crossover. I have attached a pic below of the crossover. Looking to get some direction on caps etc. all of the places I went to nearby who could do the work are talking about a 3 months wait. I know I can do the jobs. Any thoughts and opinions are welcome.
Your question brings up more questions. How do you know when to rebuild your crossovers? How long should they last? All my speakers are around 30 years old. If they are working fine I would not change anything. But, what would they sound like if you had a bad component on the crossover? Would I be able to tell with my naked ears? What would be needed to test it?
XPL 200's w DX1, XPL 160's, XPL 140's, L7's, L5's, L3's, L1's Homemade L Center, 4412's, 4406, L60T's, L20T's
With a 4312 you couldn't get a simpler crossover. It's 2 series caps with bypass caps in parallel and a pair of L pads. I would be more concerned about the condition of the L-pads than the caps. The L-pads are know to oxidize and give you intermittent drops outs, noise and level drops.
You could replace the caps with film caps at some point but I would reach for the deox can first.
Rob
"I could be arguing in my spare time"
Hello gferrellYour question brings up more questions. How do you know when to rebuild your crossovers? How long should they last? All my speakers are around 30 years old. If they are working fine I would not change anything. But, what would they sound like if you had a bad component on the crossover? Would I be able to tell with my naked ears? What would be needed to test it?
Well I would worry about L-pads first and give them a good cleaning. Most components will have some shift in value as they age but typically it's not enough where you should notice it. Electrolytic caps would probably be the worst offenders.
Resistors get hot and shift value or open. Capacitors can have an issue if they have too much voltage applied and punch trough the dielectric and short. Cored inductors with to much power can shift value but will return when less power is applied. Air core inductors can have the insulation break down and short turns just like a voice coil which is essentially the same thing. This is worst case and typical when abused.
In typical home use these parts are simply not stressed enough to damage them as long there wasn't an engineering whoops where a 5 watt resistor was used where a 20 watt is needed. Just like anything else hard use shortens their lifespan and shifts there values over time.
The only issues I have ever had with a crossover has been with L-pads for obvious reasons and it is real easy to hear.
I own some Altec gear from my father that was purchased in the 50's so passive components that are 60 years old. Still sound fine.
If you do own vintage speakers of any value I would keep the stock crossovers as is and just build new ones providing you have a schematic and equivalent parts are available. An example would be the tapped inductors which are no longer available.
The way to test would be to use JBL crossover test jig for speakers that have the test points and db levels on the Techsheets. For those that don't you could measure a good know crossover for the voltage drives or simulate them is program like LEAP. You would need the dcr values on the inductors and the typical load.
Rob
"I could be arguing in my spare time"
If the speakers are working, I'd leave them alone but if you're itching to "upgrade", refresh" and/or "refurbish" some classic collectable speakers, why stop at the crossovers? The accordion surrounds of the woofers have certainly changed their characteristics over the past 40 years or so, so maybe replace the surrounds as well. Same goes for the spiders of the woofers and mid-ranges, I doubt they have the same compliance as when new.Originally Posted by TerrapinBill
I have something useful to add. I picked up a beautiful pair of JBL L100T that had the crossovers reworked by duaneage. He put them to the t3 speck and a few other bits of wizardry. When I compared this pair against a pair of stock JBL L100T3, it was shocking. My L100t was so much more advanced in the low end, tight deep and beautifully balanced, and the mids and highs were so broad, smooth and extended. It made the T3 sound there were rugs over the front. My frequency scans I ran showed how remarkably flat they are. Picture perfect. The flattest Ive ever tested.
ive arranged to have him rework my L-80t after the holidays.
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