JBL Paper wrapped capacitor filled with wax -- what type cap is it?

[jfine]

Acquired a pair of L300's, these have 3 caps that are wax filled, wrapped with a cardboardy-paper.

I saw the thread where someone rebuilt these, and other people have just replaced them.

But what kind of cap is it inside there? Film?

I know JBL in this era used metal NP's on some models, yellow mylars on lots of models, L300 included, but if the wax caps are film, then they should still spec fairly well, like the mylars do.

[mech986]

Acquired a pair of L300's, these have 3 caps that are wax filled, wrapped with a cardboardy-paper.

I saw the thread where someone rebuilt these, and other people have just replaced them.

But what kind of cap is it inside there? Film?

I know JBL in this era used metal NP's on some models, yellow mylars on lots of models, L300 included, but if the wax caps are film, then they should still spec fairly well, like the mylars do.

I believe they are mylars encased in the wax & paper shell, but now really old mylars. I'd still suggest replacing them with some fresh polypropylenes.

[jfine]

Hmm, mylars inside eh? It looks like just some foil wrapped around something,

http://www.audioheritage.org/vbullet...l=1#post320369

I guess it's just paper,

http://en.wikipedia.org/wiki/Types_of_capacitor

I do not want polypropylenes, I would like to find a more direct replacement (not visually, functionally), IF I decide to replace.

[hjames]

Okay, the Schematic of your L300 crossover is here -
http://manuals.harman.com/JBL/HOM/Te...ummit%20ts.pdf

Just replace the caps in question with whatever kind of caps you prefer, just match the existing values.

Hmm, mylars inside eh? It looks like just some foil wrapped around something,

http://www.audioheritage.org/vbullet...l=1#post320369

I guess it's just paper,

http://en.wikipedia.org/wiki/Types_of_capacitor

I do not want polypropylenes, I would like to find a more direct replacement (not visually, functionally), IF I decide to replace.

[NickH]

Okay, the Schematic of your L300 crossover is here -
http://manuals.harman.com/JBL/HOM/Te... Summit ts.pdf

Just replace the caps in question with whatever kind of caps you prefer, just match the existing values.

Voltage can be higher on a new cap, but nont lower. And take into account the tolerance of the old and new cap.

[jfine]

Okay, the Schematic of your L300 crossover is here -
http://manuals.harman.com/JBL/HOM/Te... Summit ts.pdf

Just replace the caps in question with whatever kind of caps you prefer, just match the existing values.

I have the schematic, I know I can put whatever I want in there, but my question remains:

What type of cap is it? Must be a mystery!

[hjames]

I have the schematic, I know I can put whatever I want in there, but my question remains:

What type of cap is it? Must be a mystery!

Who cares, its an old cap that was figured at a certain price point, and is long beyond its expected lifetime ...
Use it, or replace the caps in question with whatever kind of caps you prefer, just match the existing values,
and like the man says, voltage can be higher, but never lower ....

[jfine]

Who cares, its an old cap that was figured at a certain price point, and is long beyond its expected lifetime ...
Use it, or replace the caps in question with whatever kind of caps you prefer, just match the existing values,
and like the man says, voltage can be higher, but never lower ....

I'll ask more direct this time, maybe the question is not clear enough.

What type of cap is it?

P.S. I do not want to replace it.

[mech986]

I'll ask more direct this time, maybe the question is not clear enough.

What type of cap is it?

P.S. I do not want to replace it.

You'll have to ask Greg Timbers as he helped design it and would know. However, I think we can deduce this much from your link - the caps themselves are foil wrapped which probably is the metallic side of the dialectric. There must be a non-conductive material so its either air, paper, or plastic (of some type). Given that the speaker was designed in the mid 70's, the prevailing non-electrolytic caps were mylar, metallized mylar, paper, and then a whole host of specialized materials like polycarbonate, teflon, polystyrene, and the like. Here's the drawbacks as of 1973:

polypropylene, metallized PP - very expensive as volume production not yet available, low esr, good volumetric efficiency, hard to get in smaller production quantities
Teflon - super expensive, large size, military only back then
Polystyrene - low voltage and current capability, poor volumetric efficiency (big size, low uf values), got expensive, burned easily.
Polycarbonate - low volume made, good size and efficiency, but not much available
Paper - high voltage capable, poor volumetric efficiency, tend to get leaky, rarely used in speaker crossovers
Mylar - low cost, fair volumetric efficiency, good voltage tolerances
Metallized mylar or film and foil construction - moderate cost, good to very good volumetric efficiency for a non-polar cap, decent ESR (when people thought of those things), many manufacturers.
Non-polar electrolytic - very high volumetric efficiency, sometimes decent sometimes poor tolerances in value, low cost, decent reliability, high ESR (generally) - could have been used


My sense is that they were metallized mylar caps, without the usual outer coating and end epoxy seals to keep cost down. As these were crossovers made point to point without Printed circuit boards, the ability of gluing or fixing the components in a potting material like most JBL consumer and pro crossovers of that time made the sand/cardboard tube/wax seal an easy way to deal with the cap without melting it.

Tons of caps were used, so saving money while getting the best performance relative to the cost was probably a high concern.

[4313B]

I'll ask more direct this time, maybe the question is not clear enough.

What type of cap is it?

P.S. I do not want to replace it.

They are mylars.

How about just selling those nice loudspeaker components to someone that knows what to do with them?

Just asking...

[Earl K]

- Okay ( this pic ), from the thread that you linked us to ( in post #3 ), clearly shows ( to these eyes ) a Film & Foil type construction, that ( due to it's vintage age ) has got to be made with Mylar film .

They are mylars.

Yeh, what he said .

P.S. I do not want to replace it.

Then why all this fuss ?

[jfine]

They are mylars.

How about just selling those nice loudspeaker components to someone that knows what to do with them?

Just asking...

What makes you think I should sell any of the components?

[jfine]

Then why all this fuss ?

I get the feeling I can't ask any questions unless it's because I want to replace something.

Haven't you ever been curious about something? sheesh.

[jfine]

You'll have to ask Greg Timbers as he helped design it and would know. However, I think we can deduce this much from your link - the caps themselves are foil wrapped which probably is the metallic side of the dialectric. There must be a non-conductive material so its either air, paper, or plastic (of some type). Given that the speaker was designed in the mid 70's, the prevailing non-electrolytic caps were mylar, metallized mylar, paper, and then a whole host of specialized materials like polycarbonate, teflon, polystyrene, and the like. Here's the drawbacks as of 1973:

polypropylene, metallized PP - very expensive as volume production not yet available, low esr, good volumetric efficiency, hard to get in smaller production quantities
Teflon - super expensive, large size, military only back then
Polystyrene - low voltage and current capability, poor volumetric efficiency (big size, low uf values), got expensive, burned easily.
Polycarbonate - low volume made, good size and efficiency, but not much available
Paper - high voltage capable, poor volumetric efficiency, tend to get leaky, rarely used in speaker crossovers
Mylar - low cost, fair volumetric efficiency, good voltage tolerances
Metallized mylar or film and foil construction - moderate cost, good to very good volumetric efficiency for a non-polar cap, decent ESR (when people thought of those things), many manufacturers.
Non-polar electrolytic - very high volumetric efficiency, sometimes decent sometimes poor tolerances in value, low cost, decent reliability, high ESR (generally) - could have been used


My sense is that they were metallized mylar caps, without the usual outer coating and end epoxy seals to keep cost down. As these were crossovers made point to point without Printed circuit boards, the ability of gluing or fixing the components in a potting material like most JBL consumer and pro crossovers of that time made the sand/cardboard tube/wax seal an easy way to deal with the cap without melting it.

Tons of caps were used, so saving money while getting the best performance relative to the cost was probably a high concern.

Thank you and everyone for your answers, very helpful.

[mbottz]

I did not look very closely when I rebuilt the 212 crossovers in the links above. But my opinion is that JBL purchased these in bulk and that they were probally not of high quality but were of good quality for the time. That may be the reason they were put in the cardboard and sealed up. To give the apearance of somthing special!! Technology has advanced in the last 40/50 years and even the cheaper replacements today are probally better than the factory originals were when new. I think a replacement will yield an definate improvement.

Just my opinion, take it for what it is worth.

MB