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Thread: L300/Summit Recap thoughts

  1. #16
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    Quote Originally Posted by SEAWOLF97 View Post
    reading the above, I'm wondering why you want to fix what ain't broke ?
    +1.

  2. #17
    Junior Member T.Rex's Avatar
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    Read below...........I'm not going to fix what ain't broke.......just don't want to wait to the inevitable happens and than not have any idea what to do.

    If, and when the caps go, I'll disconnect everything and have the original crossover box replaced with high end, reliable parts...that should last until I die I hope.

    I think Ian is right.........am running through a Levinson 38S Preamp and Mcintosh MC 252 Power Amp........don't want to mess with the current synergy that might be lost with an aftermarket Crossover.

    thanks,

    Tom

  3. #18
    Junior Member T.Rex's Avatar
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    MCM......you should get a medal or something for that work!.........Unbelievable workmanship.

    Macaroonie, Ian and MCM ....thanks for the help.

    regards,

    Tom

  4. #19
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    Tom,

    Unlike amps/receivers, etc. with active electronics, capacitors in speaker crossover networks rarely fail catastrophically. They typically drift over time. How much and how fast the drift depends on the quality of the original parts, operating and environmental conditions.

    So, don't expect any "a ha" moment when your speakers suddenly stop working or start sounding noticeably worse than they did the day before. The caps typically drift so slowly, you don't even notice it, until you do a recap and things suddenly sound better.

    The caps in your L300 Summits are now over 40 years old. The caps JBL used were high quality for the time, but are nothing special by today's standards. I've recapped many smaller JBLs, and to my ears, they always sounded better after the recap. In the case of the smaller speakers, the crossovers are simpler, replacement parts are cheaper and the labor involved is minimal (compared to building a pair of L300 crossovers from scratch). So, I generally do them as a matter of course when I have the woofers pulled for replacing the deteriorated foam surrounds. Gives me something to do while the glue dries and I have easy access to the crossovers.

    Unfortunately, with the L300 Crossovers potted in wax, a simple recap becomes more time consuming. You have multiple options:


    • Just leave them as they are and be content that even if the caps have drifted the speakers still sound good to your ears.



    • Replace the easily accessible caps - fortunately, the easily accessible caps are the ones in the tweeter and midrange circuits. These are more crucial to sound quality than the woofer shunt caps that are potted in the wax. This would be quick easy and relatively inexpensive. Low hanging fruit.



    • Melt the wax and do a complete rebuild of the existing crossovers.



    • Make some new crossover based on the original design.



    • Make some new crossovers based on the Nelson Pass design. If you're contemplating going this route, I suggest you read the PDF in the link I provided in my first reply. Nelson Pass is a well respected audio engineer. He knows his stuff. Even if you don't end up going this route, as an L300 owner, it's worth reading his report just to fully understand your options.


    As you move down this list, the cost of parts and time/effort involved increases.

  5. #20
    Junior Member T.Rex's Avatar
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    Hi MCM........

    The Summits still sound good to my ears, but your right....I'm sure they have drifted a tad compared to new. I'll probably, in the next few years, remove and have the whole damn crossover re-done. I don't want to replace part of it now and part later. These speakers produce some of the most realistic vocals that I have ever heard and the drivers are built like a tank. I purchased them in 2007 after looking for years for a "like new Set" and found them with an additional set of unused Camel grill covers to boot. I wipe them down with Howards Feed-N-Wax a few times a year and the Black Walnut still looks almost new. Only modification was to install high-quality banana plug jacks. They are consecutively numbered as well........

    thanks a million,

    Tom
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  6. #21
    Senior Member macaroonie's Avatar
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    Quote Originally Posted by MCM_Fan View Post
    Tom,

    Unlike amps/receivers, etc. with active electronics, capacitors in speaker crossover networks rarely fail catastrophically. They typically drift over time. How much and how fast the drift depends on the quality of the original parts, operating and environmental conditions.

    So, don't expect any "a ha" moment when your speakers suddenly stop working or start sounding noticeably worse than they did the day before. The caps typically drift so slowly, you don't even notice it, until you do a recap and things suddenly sound better.

    The caps in your L300 Summits are now over 40 years old. The caps JBL used were high quality for the time, but are nothing special by today's standards. I've recapped many smaller JBLs, and to my ears, they always sounded better after the recap. In the case of the smaller speakers, the crossovers are simpler, replacement parts are cheaper and the labor involved is minimal (compared to building a pair of L300 crossovers from scratch). So, I generally do them as a matter of course when I have the woofers pulled for replacing the deteriorated foam surrounds. Gives me something to do while the glue dries and I have easy access to the crossovers.

    Unfortunately, with the L300 Crossovers potted in wax, a simple recap becomes more time consuming. You have multiple options:


    • Just leave them as they are and be content that even if the caps have drifted the speakers still sound good to your ears.



    • Replace the easily accessible caps - fortunately, the easily accessible caps are the ones in the tweeter and midrange circuits. These are more crucial to sound quality than the woofer shunt caps that are potted in the wax. This would be quick easy and relatively inexpensive. Low hanging fruit.



    • Melt the wax and do a complete rebuild of the existing crossovers.



    • Make some new crossover based on the original design.



    • Make some new crossovers based on the Nelson Pass design. If you're contemplating going this route, I suggest you read the PDF in the link I provided in my first reply. Nelson Pass is a well respected audio engineer. He knows his stuff. Even if you don't end up going this route, as an L300 owner, it's worth reading his report just to fully understand your options.


    As you move down this list, the cost of parts and time/effort involved increases.

    OR ......

    Buy 3 x ML 11 in good nick and a DBX / JBL Urei 260 crossover and DSP the living crap out of them.

    Well , perhaps a ML9 for the Bass

    oops thats only 5K £££$$$eee

  7. #22
    Senior Member Ian Mackenzie's Avatar
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    I think they look really great.

    In fact l am going to look around for a pair to go in the family room!

  8. #23
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    Quote Originally Posted by T.Rex View Post
    Hi MCM........

    The Summits still sound good to my ears, but your right....I'm sure they have drifted a tad compared to new. I'll probably, in the next few years, remove and have the whole damn crossover re-done. I don't want to replace part of it now and part later. These speakers produce some of the most realistic vocals that I have ever heard and the drivers are built like a tank. I purchased them in 2007 after looking for years for a "like new Set" and found them with an additional set of unused Camel grill covers to boot. I wipe them down with Howards Feed-N-Wax a few times a year and the Black Walnut still looks almost new. Only modification was to install high-quality banana plug jacks. They are consecutively numbered as well........

    thanks a million,

    Tom

    Tom,

    Wow, those really are beautiful. JBL really made some great cabinets back in the day. Of course back then everything from the drivers to the boxes were top notch.

    I've also installed new binding posts on every pair of vintage JBLs I've owned. If there was a weak spot, that was it. Fortunately, it's easily corrected.

  9. #24
    Administrator Robh3606's Avatar
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    Wow I forgot just how nice those speakers look!

    Rob
    "I could be arguing in my spare time"

  10. #25
    Senior Member 1audiohack's Avatar
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    Dang those really are gorgeous!

    Barry.
    If we knew what the hell we were doing, we wouldn't call it research would we.

  11. #26
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    IMHO, the yellow mylar caps on top and the wax filled caps in the resin filled box are likely fine. There's no electrolytics in the L300 to worry about. But if you want to play, and possibly achieve better sound...

    With patience, you can carefully remove the yellow mylars on top intact, and simply carefully disconnect the wax filled caps from the terminals, making sure it can all be put back to stock if that's a concern. Then you can strategically use the top of the box for mounting caps/resistors. I left the cores alone since there's a special one in there with an extra lead, I think the nelson pass design got rid of that. Anyway contact Jeff @ SonicCraft. He can help achieve what you are looking for in cap selection. If you want excellent sound, then you need xcellent caps/resistors, not the solens dayton clarity stuff. Also think about using quality wire specially for the LPADS, and the LPADS really need inspection to make sure they're functioning properly too.

    All IMO.

  12. #27
    Junior Member T.Rex's Avatar
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    Thanks Jfine....I'll keep that in mind.

    regards,

    Tom

  13. #28
    Junior Member T.Rex's Avatar
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    Couple more pics...........Look how beautifull those cabinets are. Boy, those were the days.
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    Name:  l300 (1).jpg
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