JBL OEM film caps used in L19 / 4301 and other 70-80's era - paging 4313B or GT

[mech986]

So I'm on AK and an update pops up in a JBL L19 mod thread. Here's the verbatim post, with my emphasis:

I need to correct this mistake for future readers. Do not taint your JBL L19 speakers with awful new capacitors. The originals do not need replacing - and any other capacitor will be a downgrade. The original are stacked-film caps, with hand-soldered teflon leads, in a sand-damped cardboard tube which has been sealed with wax. It doesn't get more luxurious than that. Don't put your audiophoolery filth in these old speakers - you do not know better than JBL's designers.

Er, AFAIK, and I think the JBL literature of the era backs this up, the cardboard tubed caps were mylar or polyester, of no particular fancy construction other than being wound, and then sealed for ease of assembly as "radial" standup units. I may grant that the capacitors would need to be hand soldered with extending wire leads but I cannot find any evidence that JBL's suppliers (usually sourced from US and Mexico, makes Chicago, IMB, Electro-Cap, etc.) used anything but plain tinned copper wire with common pvc or similar insulation.

I have a number of JBL crossovers and have examined the caps and their wiring closely. The wire insulation is very flexible and has a matte or flat appearance and a drag texture to it, indicative of thin PVC, not Teflon (TPFE) insulation which tends to be glossy in appearance and has a very slippery feel. Also, the original cap wiring is easy to cut and strip, while Teflon insulated wire is difficult to cut, even in smaller gauges. While the wire is quite silvery and shiny, I see no evidence of silver plated copper wire as would be found with Teflon insulation.

Although JBL was on the leading edge in terms of crossover knowledge and used mylar caps extensively from the late 50's on (probably the only speaker maker to do so), the advent of boutique capacitors was still not fully appreciated till the Jung/March article in Audio, circa 1978 or so, and still did not see wide use in crossovers for another decade. As for stacked film caps, AFAIK, they would have been made from mylar, they weren't widely available in the 70's and because of their construction, they don't offer a high volumetric efficiency for large values (above say 2uf). I haven't been able to find ANY stacked film caps in sizes above 2uf as their construction and use is primarily for PC board use. I suspect they would have been too expensive to build, purchase, and use, especially for values typically used in crossovers.

Another reason why the typical cardboard encased cap is not likely exoticly built or an exotic material is the simple fact that JBL would have touted their use in their product literature, consumer or professional, and discussed the merits of the type of material, construction, and use. JBL DID discuss use of bypass caps, eventual polycarbonate and polypropylene bypass in the 80's, as well as crossover topology when they were used on select models.

The last factor arguing against exotic is simply cost. Although JBL could certainly specify and buy in bulk and get the highest quality, even back then, costs mattered, especially in the consumer lines. It would make little sense for JBL to specify and use exotic caps in the L19/4301 at those lower price levels. The L100 of the early 70's used similar caps and the tech was even less known then.

Here's a couple of older threads which discuss the cap issue and thanks to mbottz for the helpful deconstruction of the OEM caps that look tubular and have no end plate as would stacked film types.

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

http://www.audioheritage.org/vbullet...type-cap-is-it

[mech986]

A couple of other observations:

Four caps that I have removed from old 4301/L19 crossovers have had cut and stripped wire ends. they have remained shiny for at least 3 years. IF there was teflon insulation, it would oxidize the copper wire, so the wire usually would have been silver plated copper which would still oxidize when exposed over time. This leads me to believe they are tinned copper wiring.

Certainly the other issue is the cost of using teflon insulated wires, and I don't think JBL was in the habit of buying up military surplus mil-spec wiring.

[Alobar]

Hopefully will get some good opinions on this subject and even better some sort of consensus on whether to recap or not. I have some L200's that still sound fine to me but at 42 years old always wonder if any improvement could be gained from rebuilding their xovers. The last thing I want to do is make them worse...

"Do no harm".

[Steve Schell]

Just a note from the memory bank... I once photographed some of Greg Timbers' experimental crossovers, but lost the images later (I think) in a hard drive crash. Greg took copper plated circuit board material, made many shallow vertical and horizontal cuts with a saw to isolate many square sections, and puddled solder and tacked components in place to build a circuit rapidly for testing. Genius! He also had many shelves full of bin boxes of inductors, capacitors and resistors so that he could "grab and go" when building. He would test, swap components, test, swap components, test etc. until he had the circuit he wanted.

[4313B]

I bought the exact same capacitors from JBL and IMB Electro-Cap, depending on who had what values in stock. They were metallized mylar.

It is entirely possible that the person who posted that on the other website replaced some of those old mylar capacitors with some fancy new capacitors and didn't like the results.

Today I would simply bias the L19 or 4301 network using metallized polypropylene capacitors and thoroughly enjoy the results.

[4313B]

Just a note from the memory bank... I once photographed some of Greg Timbers' experimental crossovers, but lost the images later (I think) in a hard drive crash. Greg took copper plated circuit board material, made many shallow vertical and horizontal cuts with a saw to isolate many square sections, and puddled solder and tacked components in place to build a circuit rapidly for testing. Genius! He also had many shelves full of bin boxes of inductors, capacitors and resistors so that he could "grab and go" when building. He would test, swap components, test, swap components, test etc. until he had the circuit he wanted.

Yep, and on that note people should realize that he was listening to metallized mylar capacitors at the time. Then he started using metallized polypropylene mains along with polypropylene and polystyrene bypass capacitors. And IMB Electro-Cap had them all available. I tried out every single one of them. Now he uses biased metallized polypropylene capacitors.

Also note that JBL started using N.P. electrolytic capacitors for the large values used in the conjugate filters. These were invariably bypassed with the appropriate smaller poly capacitors.

[mech986]

thanks for the comments. Can anyone make a specific comment on the claim that the OEM caps were stacked film construction vs. typical conventional wound, and on the use of Teflon insulated wire?

IIRC, most wire insulations use a pvc or polyethylene which will melt or burn when flame exposed. Teflon, IIRC, has a self extinguishing property (halogenated) so is almost flame retardant.

[4313B]

Yeah... and the cardboard tubes were recycled from the Queen's Royal Toilet Paper Tubes... a special Electro-Cap envoy respectfully collected each cardboard tube as the Queen finished a roll of toilet paper and transported the cardboard tube back to America in a gilded box lined with the finest silk where is would then be made into one of these luxurious capacitors.

Seriously, they're metallized mylar, who really gives a **** how they are made? At the very least do yourselves a favor and put 0.01 uF polypropylene bypass capacitors in parallel with them.

Oh, and stop reading stupid **** on the Internet.

[mech986]

I understand you position, I'm just trying to gather evidence, logic, and reason against all points put forth by that poster before I respond to him. the only way to counter Magical audiophile thinking is to provide facts, and even then, people don't change their minds if they aren't open.

[4313B]

I understand you position, I'm just trying to gather evidence, logic, and reason against all points put forth by that poster before I respond to him. the only way to counter Magical audiophile thinking is to provide facts, and even then, people don't change their minds if they aren't open.

I wouldn't even bother responding to him. Nobody cares what he does with his L19's. The information was posted many years ago and if people like this guy just don't get it, screw 'em. It quite simply isn't your problem. These clowns will argue with you until the end of time if you let them. It's what they do...