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Thread: Nelson Pass Crossover for L 300 Summit

  1. #1
    Junior Member Tedz's Avatar
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    Question Nelson Pass Crossover for L 300 Summit

    I'm looking for someone who can build me a set of crossovers. Is there anyone out here who can build me a pair ?

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    Quote Originally Posted by Tedz View Post
    I'm looking for someone who can build me a set of crossovers. Is there anyone out here who can build me a pair ?
    Hi, I'm not convinced the Nelson Pass design is any better than stock. You might be better off upgrading the film caps and all the wire including the wire to the LPADS.

    In the end, I found bone stock sounded the best, even though upgraded caps/resistors/wire gave better resolution and heightened presence.

    Resoldering all the xover points on the xover box by sucking off the old solder and using quality solder might also give good results, that alone evened out things much better between the 2 cabinets.

    IME.

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    Junior Member Tedz's Avatar
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    Quote Originally Posted by jfine View Post
    Hi, I'm not convinced the Nelson Pass design is any better than stock. You might be better off upgrading the film caps and all the wire including the wire to the LPADS.

    In the end, I found bone stock sounded the best, even though upgraded caps/resistors/wire gave better resolution and heightened presence.

    Resoldering all the xover points on the xover box by sucking off the old solder and using quality solder might also give good results, that alone evened out things much better between the 2 cabinets.

    IME.
    I would but I don't want to alter the OEM crossovers. The crossovers and cabinets are consecutive serial numbered.

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    Quote Originally Posted by Tedz View Post
    I would but I don't want to alter the OEM crossovers. The crossovers and cabinets are consecutive serial numbered.
    To me, it's more trivial to alter the OEM crossover in a way that you can revert it back to stock, vs creating a new crossover network.

    Using the existing inductors alone makes it easier, (and nevermind that the Pass design omits the special midrange 3 wire inductor), and then updating the caps/resistors by simply and carefully disconnecting the caps that are in the box underneath at the terminals, and carefully removing the yellow mylars (don't just snip them). It's just soldering vs creating and buying all the inductors, caps, resistors, and then you still have about 3 + feet of wire from the xover up to the LPADS and back, plus all the driver wires, unless you just want to tackle caps in which case you could just modify the OEM with care.

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    Administrator Mr. Widget's Avatar
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    I definitely would rather build new and preserve the original networks for any speaker as collectable as the L300. They keep going up in value. That will likely change when we all die off, but then our heirs will have to deal with these gigantic speakers and good luck to them. As long as we are around there will likely be a good market for original L300s.

    As far as which network is better? I haven't heard the Nelson Pass crossover, but the vintage JBL networks I have had were pretty much the weakest link in every one of my vintage JBLs. I'd bet Nelson's is an upgrade.


    Widget

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    Quote Originally Posted by Mr. Widget View Post
    I definitely would rather build new and preserve the original networks for any speaker as collectable as the L300. They keep going up in value. That will likely change when we all die off, but then our heirs will have to deal with these gigantic speakers and good luck to them. As long as we are around there will likely be a good market for original L300s.

    As far as which network is better? I haven't heard the Nelson Pass crossover, but the vintage JBL networks I have had were pretty much the weakest link in every one of my vintage JBLs. I'd bet Nelson's is an upgrade.


    Widget
    I agree that preserving the original network in a speaker as collectible as the L300 is wise from a standpoint of preserving the (sale) value of these speakers.

    There also is no doubt in my mind that a better network can be designed and built, given enough time, knowledge, skill, and instrumentation. The original network however was designed by a man who from his own writings always loved network design, it was one of his strengths, and by the time the Summit was designed was well entrenched and able to spend money where he saw fit in these networks, I believe that it will be difficult to do better. Nelson Pass wrote in his article about his L300 Summits, after he spent significant time with several iterations of his crossover for the L300s that (I paraphrase not having the article in front of me) he wasn't sure that his design made enough difference to be worth the time invested. That in Nelson Pass's own space, not your living room, which would of course need its own tweaks to fit your LR's acoustics and your system's nuances.

    Is it worth all that he put into it? Likely yes at this point as we are experimenters and love the chase. However also note that Nelson Pass's L300s were L300As, apparently original 136A cones that were only re-foamed. Many L300s have at this point been re-coned with 2235H cones (with and without the mass ring), still more are the considerably different L300A speakers with the ferrite magnet, which should be a complete start-over for Mr. Pass's journey, and there are of course the re-coned with 2235H L300As like mine that are another level and should have a still different design from Mr. Pass's iterations.

    I am able to see "flat" response from 26Hz to 20kHz with very good phase coherence from mine with the original crossovers, 2235H woofers, in my listening room (minus one 50Hz reflection that was causing an out-of-phase cancellation at first). It surprises me how flat the graph is, considering the cone is not the original 136H but instead the 2235H, must be very close to the original above 30Hz. To go any further I would be using my DSP and bi-ampng or tri-amping anyway, it seems that duplicating Nelson Pass's process on my version of this speaker in my space and on my equipment is more than I'm willing to do. Just my experience and opinion.

    On the 4333 OTOH, I'd already be tri-amped.
    - Jeff

  7. #7
    Senior Member duaneage's Avatar
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    I've built several sets of Pass crossovers for the L300. I've even done a bi amp version.
    If you are interested in a set on PCBs PM me and I can help you. I've also done sets with new pots as well.

    A B comparison was definitely different and I think it improved the midrange performance. I do agree in keeping the old networks for reference as well as resale value.
    Why buy used when you can build your own?

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    Quote Originally Posted by Tedz View Post
    I'm looking for someone who can build me a set of crossovers. Is there anyone out here who can build me a pair ?
    Pairs of crossover PCBs that incorporate both the Nelson Pass modification and the charge-coupled (biased) capacitor technique, well documented here on LH, are available on eBay:
    https://www.ebay.com/itm/JBL-L300-43...-127632-2357-0

    (not my listing; no affiliation)

    They are bare PCBs only; you’d need to order the parts and solder them up yourself, but they appear to fit inside the stock cabinet, using the stock mounting features, and you’d be able to keep your original crossovers intact in a safe place.

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