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Thread: L300/Summit Recap thoughts

  1. #1
    Junior Member T.Rex's Avatar
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    L300/Summit Recap thoughts

    Hi all,

    I have a lovely set of Summits and was wondering about recap longevity. I know that this is going to vary, but want to keep my options open for the future. My Summits have worked flawlessly since I purchased back in 2007 as the 2nd owner........no cracks, pops.....nothing. Even the L-Pads, after treating with a little deoxit work like new. I also know that capacitors don't last forever. These are pushing 40-years old now and probably only a matter of time. I play every day, never really pushing them in a controlled environment.

    How hard to disassemble crossover and remove board?...........Should I have the caps replaced on the original board or will a new board built for the job be the better route?.....Does anyone have any experience with the Pass-Nelson Board that is listed on Ebay/Amazon?.....will it directly fit into speaker or are their mods needed? (Pic Below)......Does anyone have any experience with the sound quality with this change?

    I don't want to have to haul these heavy behemoths to a repair center.........how much is involved with the upgrade and could an electrician possibly be hired to replace for me?

    I know I'm asking a lot of questions and seems funny since these speakers work fantastic as I write this.

    Thanks,

    Tom

    Product description

    Crossover for JBL L300 summit century 3 way speaker system! ( pair)
 
Welcome back to the sound of the century! We have decided to put together a " top quality crossover that will match the specifications of the JBL L300 ( modified version) , since it has a better frequency response and sound.. this crossover will work and sound just like back on the 70"s, but just built with new top quality components this days. sweet sound on the highs, clean and projected vocals on the midrange and the great boom, tight punchy bass on the lows. heavy duty 250 volt capacitors, high temp inductors and heavy duty resistors that will last for a long period of time. this crossover will have the feature for you to ad the L-Pads on the tweeter and the Mid, just like the original! specs: • 3 way crossover network system
 • crossover frequencies 1.2khz & 8khz 
 • 500 watts RMS / 1000 watts peak 12db/oct
 • to use with 8 ohms drivers
 • built and based on the " modified version of the "JBL L 300 "
 • heavy duty Bugle "J" 250 volt Metallized Polyester Film capacitors
 • orifices built on board for tweeter&mid for L Pad easy installation 
 • dimensions 4 3/4" X 6 3/4
.


    Attached Images Attached Images  

  2. #2
    Senior Member macaroonie's Avatar
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    Is your crossover is the same as N333 , essentially a steel box with all the components inside and a wiring loom going to the drivers ? If so you will find that the bass section caps and chokes are potted in wax in the bottom of the box. It's quite the process to extricate the relevant parts as you need to melt the potting and clear it out .

    I did it with 4315 networks and it was a pita. You will need to be very meticulous
    as to what wire goes where. Take loads of pics as you go and refer to the schematic.

    It can be done , but take care.

    BTW , if you have a woodburner with it on at a lazy heat you can heat the whole caboodle till the wax melts.

  3. #3
    Junior Member T.Rex's Avatar
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    [QUOTE=macaroonie;415616]Is your crossover is the same as N333 , essentially a steel box with all the components inside and a wiring loom going to the drivers ?


    Yep....Steel Box with wiring loom............Can I remove the whole box and remove from the cabinet and work on the crossover or is it riveted or non-removable?

    thanks for your help,

    Tom

  4. #4
    Senior Member macaroonie's Avatar
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    [QUOTE=T.Rex;415620]
    Quote Originally Posted by macaroonie View Post
    Is your crossover is the same as N333 , essentially a steel box with all the components inside and a wiring loom going to the drivers ?


    Yep....Steel Box with wiring loom............Can I remove the whole box and remove from the cabinet and work on the crossover or is it riveted or non-removable?

    thanks for your help,

    Tom
    Yeah it will disconnect and de mount. Screws probably. You will see a perf top plate on the box , thats when you need to start taking notes. Depending on the age the components may not have values printed on them but they will have part No's. You then need to refer to find that part in the schematic.

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    Junior Member T.Rex's Avatar
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    Thanks.....When it comes time, or when I'm in a adventurous mood I will remove and have them rebuilt. I'm guessing that there are no spade connectors...just wires? So I'll have to cut, label and splice when I re-install?

    thanks,

    Tom

  6. #6
    Senior Member macaroonie's Avatar
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    You can de mount the whole x/o complete with driver wiring. Once you start to take the
    x/o to bits ,after you remove the perf cover you WILL have to start de soldering to get the tag board out of the way and then you are in to the potted components.

    At each solder lug / tag you must ID the wires , some come from down below in the wax.

  7. #7
    Junior Member T.Rex's Avatar
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    If I have someone else recap these can I just remove the box with wires attached and have the tech do all the de-soldering? Also It looks as though the drivers are connected with spades...right? Are the Mid/Treble connections to the Brilliance and treble controls on the front simply soldered at their ends? From the pictures it looks like there is 1 wire coming from the crossover assembly leading to the 2. Does this wire branch out so that I can label the wires? I do not want to remove the front folical if at all possible.

    thanks,

    Tom

  8. #8
    Senior Member SEAWOLF97's Avatar
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    Quote Originally Posted by T.Rex View Post

    I have a lovely set of Summits and was wondering about recap longevity. I know that this is going to vary, but want to keep my options open for the future. My Summits have worked flawlessly since I purchased back in 2007 as the 2nd owner........no cracks, pops.....nothing. Even the L-Pads, after treating with a little deoxit work like new. I also know that capacitors don't last forever. These are pushing 40-years old now and probably only a matter of time. I play every day, never really pushing them in a controlled environment.
    reading the above, I'm wondering why you want to fix what ain't broke ?
    It's easier to try than to prove it can't be done

  9. #9
    Senior Member Ian Mackenzie's Avatar
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    That’s a good point.

    It’s about your desires and expectations.

    Today’s film quality crossover capacitors are superior what’s in that original network.

    In light of other attempts to update the L300 crossover it might pay to first research & document all the wires from the L pads to the network and from the network to the drivers and rear terminals. Assuming you are not considering selling them any time soon arrange a new network to be built. The charge coupled version of the existing network would be a good place to start. I would simply cut the lead-in wires to the network and use a terminal block strip to connect the new network to all the existing wires.

    The complexity of sorting out what goes with what in those old networks is a bit much. They were not built to be modified by diy people.

  10. #10
    Junior Member T.Rex's Avatar
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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 ?
    I don't.......I am just keeping one step ahead when the time comes. I never plan on selling these. I was just stating that caps don't last forever and I want to be prepared when the time may come........

    thanks!

  11. #11
    Senior Member Ian Mackenzie's Avatar
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    If you still use the ML preamp and associated equipment a network re build is justified.
    I personally would not buy a prefabricated crossover off eBay in your situation.

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    JBL L300 Nelson Pass Crossovers

    How handy are you? I recently built a pair of L300 crossovers based on the Nelson Pass design. It was a LOT more work than anticipated. The mechanical assembly and making the new wiring harnesses were quite time consuming. The gentleman I built these for wanted to preserve the original crossovers and also wanted the Pass crossovers to have biamp capability.

    Here's some photos of my work:







    Wiring harnesses and main terminal block:







    Note: the leads to the midrange driver (labeled 3 and 4) are deliberately swapped as the Pass design required the midranage be connected out of phase with the woofer and tweeter drivers.


    Test setup using generic drivers to test basic functionality and operation of the L-Pads:



    One of the replacement terminal plates with Biamp Capability:



    It was a lot of work, but if you can read a schematic, are handy with a soldering iron, and have access to a table saw and a drill press, they might not be THAT much more work than de-potting and rebuilding the stock crossovers.

  13. #13
    Junior Member T.Rex's Avatar
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    Wow MCM.....too much for me to do. Very nice job though.....how does it sound? I may just have the original crossovers rebuilt when the time comes.

    thanks!

    Tom

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    Quote Originally Posted by T.Rex View Post
    Wow MCM.....too much for me to do. Very nice job though.....how does it sound? I may just have the original crossovers rebuilt when the time comes.

    thanks!

    Tom
    I haven't actually heard them. The gentleman I built them for lives over 2000 miles away, but he is very pleased with how they turned out.

  15. #15
    Member Fitero's Avatar
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    Beautiful work MCM!

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