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    JBL L26 speaker restoration

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    wildiowa

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    JBL L26 speaker restoration

    Post by wildiowa on Thu Dec 29, 2016 7:16 pm

    I dug out an old pair of JBL L26 two-way speakers and plan to rebuild them for my daughter, who is going vinyl. I ordered recone kits for the woofers and knock-off replacement tweeters and will refinish the cabs. But don't know if I should mess with the crossovers. They are hard to get to and I believe are glued and stapled on the inside front baffle...anyone know for sure on this? Even then the most I would do is replace the caps, if that is even needed. There is a guy with an upgraded crossover from Denmark but don't want to spend that much $$. While they are torn down I hate to not do everything, but it will be a hassle and could break the board etc. just trying to get it out. What would you guys do? Thanks.

    GP49

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    Re: JBL L26 speaker restoration

    Post by GP49 on Fri Dec 30, 2016 3:25 am

    How about waiting until you have the woofers out, then see for sure if they are really that difficult to get out.

    wildiowa

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    Re: JBL L26 speaker restoration

    Post by wildiowa on Fri Dec 30, 2016 8:20 am

    They are totally torn down and I am peeking through a 10" hole into a mirror trying to get a view of them on the front baffle. Appears they are held by glue and staples. Sorry to hijack the board on this but I do respect the opinions and views of all on here. I am just generally wondering if it's worth replacing caps on a crossover as we do in the amps. So much voltage running through the amps, but no so much on a crossover....do they go funky as well? If this was easier there would be no issue.
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    Kentley

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    Re: JBL L26 speaker restoration

    Post by Kentley on Fri Dec 30, 2016 10:00 am

    Crossover caps most definitely go south, and it's particularly awful when the speaks have sat idle for any considerable time. I blew a mid in my B&Ws recently from this nasty syndrome. And they were only 25 years old. Premature senility.
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    Peter W.

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    Re: JBL L26 speaker restoration

    Post by Peter W. on Fri Dec 30, 2016 10:50 am

    Absolutely replace everything on the crossover but the inductors, if any. If there is a pot or selector switch, clean it thoroughly. The caps will be non- polarized, and it really helps to select for 5% caps or better. JBL speakers are not my favorites, being "California" sound, but they are generally well made and your daughter could do much worse. Well worth the effort.

    When you get the woofers out, carefully remove all the batting, taking pictures as you go for replacement. Then you will have space and a good view to deal with the crossover.

    Good luck with them!
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    corndog71

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    Re: JBL L26 speaker restoration

    Post by corndog71 on Fri Dec 30, 2016 11:29 am

    Technically, using non-original drivers should require a whole new crossover tuned to the new drivers. Even with new caps and resistors the crossover may not match the new drivers. Better performance can be had by just buying newer speakers.

    If you contact JBL you should be able to get a schematic for the crossover and perhaps optimal drivers for those cabinets. I would definitely replace the caps, resistors. If you have the circuit then toss the old board and just wire them point to point. Secure them to a small piece of pegboard and screw it into the cabinet interior.

    Like this:


    wildiowa

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    Re: JBL L26 speaker restoration

    Post by wildiowa on Fri Dec 30, 2016 11:44 am

    Thanks everyone...looks like I try and get them out...all I have to say is, grrrrr. I am reconing the original woofers but alas, the original radiator tweeters are long gone...I ordered two similar replacements from Simply Speakers, not quite the JBLs but they recommend it as a replacement on the L26 if all else fails and very similar cosmetically. Technically I probably need to tweak the crossovers given the replacement of the original speakers but not quite that talented and getting them up and running is sufficient for a kid in a NYC apartment.

    There is quite a bit of info on this speaker on the web and I have seen some who say you just start prying the crossover with a putty knife or spatula and pull them up. You just can't see anything in there, that is the problem and there is a pot sticking out the front to adjust the high end balance on the crossover board so who knows....I do think these are worth reclaiming, though...will refinish the cabinet and should look good although the front covers are also lost. Recone kit for the 10" woofer was $60, new radiators $75 each. So I will have about $300 in them by the time I get done if I go with the caps, but it does seem to be a quality speaker. And I like to mess with this stuff.

    GP49

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    Re: JBL L26 speaker restoration

    Post by GP49 on Fri Dec 30, 2016 12:17 pm

    I would add that if it gets too difficult and if they are plastic film capacitors, you could let them be.  Electrolytics should be replaced.  Bipolar electrolytics for use in AC circuits such as crossovers have an even higher failure rate than common unipolars and by now are probably far off-value.  If one of them used as a high-pass filter in the tweeter circuit fails shorted, your tweeter will tweet (shriek) one final time as it is fed low frequency energy.

    Plastic film capacitors are far more stable, tighter-toleranced, and age far better...though I had one in a direct-drive turntable, which appeared to be operated well under its working voltage, that failed on several samples.  Even Mercedes-Benz break down (actually they are not a sterling examplar of reliability!) . And Toyota has had engineering gaffes.

    wildiowa

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    Re: JBL L26 speaker restoration

    Post by wildiowa on Sat Dec 31, 2016 2:18 pm

    Update...got the crossovers out with minimum damage. There is only one capacitor in there, it looks to be 8mf. Both leads are coming out of one end...is this a radial cap? Also I see it looks to be unpolarized.

    I plan to order two:

    8mf,
    metal polypropylene,
    unpolarized,
    +/-5%,
    100 vac,
    100 vdc caps...

    sound OK? Are these essentially Orange Drops? Those are fairly cheap....I am kind of in the dark here, thanks for the help...recone kits arrive today..

    ia.
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    corndog71

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    Re: JBL L26 speaker restoration

    Post by corndog71 on Sat Dec 31, 2016 2:45 pm

    Can you post a pic?

    GP49

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    Re: JBL L26 speaker restoration

    Post by GP49 on Sat Dec 31, 2016 2:48 pm

    Orange Drops are polypropylene film capacitors but polypropylenes are made by many manufacturers and sold through many distribution routes at many different quality grades and price points.  It's good that the ones you got are close-tolerance at ±5%.

    Yes, both leads out one end is a radial capacitor.  If you could only source axials, you could have simply bent one of the leads back upon the body of the capacitor, extending it by soldering on more wire if need be, and insulating with tape.

    I've done that a lot. Sometimes you just have to use what you've got!

    wildiowa

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    Re: JBL L26 speaker restoration

    Post by wildiowa on Sat Dec 31, 2016 7:45 pm

    I joined Photobucket and tried and tried to post a photo, but the best I can do is this link which will take you there if you copy and paste. It is a simple crossover, a couple of coils and one cap, and the pads for the attenuation. What is this type of capacitor? Is an Orange Drop OK for a replacement or should I get something else? THANKS.  IA. And Happy New Year!!


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    Dave_in_Va

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    Re: JBL L26 speaker restoration

    Post by Dave_in_Va on Sat Dec 31, 2016 10:05 pm

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    Peter W.

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    Re: JBL L26 speaker restoration

    Post by Peter W. on Sat Dec 31, 2016 10:31 pm

    Orange Drop is fine. No worries.

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    corndog71

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    Re: JBL L26 speaker restoration

    Post by corndog71 on Sun Jan 01, 2017 4:08 pm

    I know you don't want to spend a lot but I think it would be worthwhile to replace all of that.

    The pot, the cap and get some air core chokes and spread them out a bit preferably with the couls perpendicular to each other. ERSE is a good source for the caps and coils and reasonably priced.

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    Peter W.

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    Re: JBL L26 speaker restoration

    Post by Peter W. on Sun Jan 01, 2017 4:47 pm

    Inductors can be measured and do not deteriorate any more than a transformer would. If you do not have an LCR meter, test them with a VOM. Anything other than dead ( 0 ohms ) short or open = good for your purposes.

    Replace the rest as you see fit, but the caps absolutely.

    As to crossovers, they are not as closely 'tuned' as one might think in the case of a 2-way speaker, they pretty much serve to cut off the woofer at a specific frequency, with *everything else* going to the tweeter. Hence, no need to fuss with cap values beyond OEM w/in 5%. Your woofer has not changed, so *everything else* still goes to the tweeter. Were this a 3-way speaker, there might be some argument to change values 'tuned' to the replacement tweeter - but a replacement mid-range would be grounds for more concern that way.

    I do keep an LCR meter - I bought it purely on a whim for $5 at a surplus sale, and now find that I use it at least a few times per month. It is a B&K hand-held that a large electronics assembly shop in the Philadelphia region (they still exist) was replacing en-mass. Calibrated the year I bought it, and has held up ever since. But, if one comes across one where you can kick the tires (test it with known-values) and it is reasonably priced, grab it.

    GP49

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    Re: JBL L26 speaker restoration

    Post by GP49 on Sun Jan 01, 2017 5:35 pm

    Peter W. wrote:
    As to crossovers, they are not as closely 'tuned' as one might think in the case of a 2-way speaker, they pretty much serve to cut off the woofer at a specific frequency, with *everything else* going to the tweeter.

    Actually, not; you've got it backwards. A series capacitor is always used in the tweeter circuit to block low frequencies, else they would go to the tweeter and fry its tiny voice coil, as they constitute a much higher power than the tweeter is designed to handle (exception: piezo tweeters whose impedance rises rapidly at lower frequencies and thus block current flow in the bass).

    The woofer is often allowed to run full-range, as the thinking is that its high moving mass reduces high frequency response, all by itself.

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    Peter W.

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    Re: JBL L26 speaker restoration

    Post by Peter W. on Sun Jan 01, 2017 9:26 pm

    GP49 wrote:
    Peter W. wrote:
    As to crossovers, they are not as closely 'tuned' as one might think in the case of a 2-way speaker, they pretty much serve to cut off the woofer at a specific frequency, with *everything else* going to the tweeter.

    Actually, not; you've got it backwards.  A series capacitor is always used in the tweeter circuit to block low frequencies, else they would go to the tweeter and fry its tiny voice coil, as they constitute a much higher power than the tweeter is designed to handle (exception: piezo tweeters whose impedance rises rapidly at lower frequencies and thus block current flow in the bass).

    The woofer is often allowed to run full-range, as the thinking is that its high moving mass reduces high frequency response, all by itself.


    You are, of course, correct. My only excuse is strong drugs (temporary) for a hopefully equally temporary condition.

    In the words of my Irish Mother - Treat a cold and it goes away in 7 days. Leave it alone, it takes about a week.

    Thank you for setting the record straight!

    Dogstar

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    Re: JBL L26 speaker restoration

    Post by Dogstar on Mon Jan 02, 2017 11:55 am

    Just out of curiosity when were L26's on the market?

    wildiowa

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    Re: JBL L26 speaker restoration

    Post by wildiowa on Mon Jan 02, 2017 12:59 pm

    I would guess mid to late 1970's. There was also an L36 model with two woofers as I recall and others in this line. They were intended to take on Advents which were super popular at that time. If you are a child of the 60's you will remember JBL also included a menu of garish colors for their front grilles on these models including the traditional black and brown, but also electric orange and maybe even a green or something to match your orange shag carpeting. They are solid wood except for the front and back baffles and the woofers are cast aluminum so it's a pretty good box to start with. Mine were outside in a trailer for about 15 years in Iowa winters and summers...they smell seriously musty and I have them totally torn down and spraying shellac and other sealers into the interior and on the back and front to seal the smell....will paint the baffles and am sanding out the veneer to re-stain and seal.

    This is a total rebuild with recones and replacement tweeters. Found a couple 8.2 mf crossover caps from Parts Express and I'm off and running. On a cold windy winter day i will start the recones....a little apprehensive on the JBLs I have not done one yet and they say the voice coil tolerances are very very tight...we will see! if you guys haven't done a recone you should give it a try find an old scab speaker laying around and for $40 or $50 you can see if you can bring it back to life. What a hoot when you fire it up and it is restored! Or maybe I have been breathing too many fumes from the glue pot....
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    Rabindu

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    Re: JBL L26 speaker restoration

    Post by Rabindu on Mon Jan 02, 2017 4:23 pm

    I have a pair of L36's which my father bought back in '78. I have since re-foamed the woofers with great success and love their sound. They are 3-way with the standard tweeter, mid driver and one 10" woofer. I find that they are a very bright sounding speaker therefore have the brilliance and presence greatly attenuated otherwise ear fatigue sets in quickly. Bass is nice and tight and my VTA ST-120 has no problems driving them. JBL lists their efficiency as 76db/1watt at 15' which doesn't sound good until you realize the measurement is at 15'. I wonder what that might translate into using the standard 1 watt @ 1 metre method. They were considered a great sounding speaker back in the day and still sound every bit as good today.

    Mike

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