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Thread: JBL L250 crossover upgrade to 250Ti specifications

  1. #1
    Junior Member Rpower's Avatar
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    JBL L250 crossover upgrade to 250Ti specifications

    I had already installed the 044Ti and 104H mid drivers in my L250s, but without the crossover upgrade the speaker's sound was out of balance. Since I was unable to find any 250Ti crossovers to purchase, I decided to upgrade the L250 crossovers to 250Ti specs. It took me a couple of weeks to acquire the parts and working in my spare time to accomplish, but I am extremely pleased with the results. The sound is magnificent and the upgrade was well worth the effort. Thanks for the help from other members.
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    Junior Member Rpower's Avatar
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    More details on 250 crossover upgrade...

    I spent several weeks studying and contrasting the L250 and 250Ti schematics and pics and saw a direct one-to-one parts swap for most all the components. Also having the part numbers on the PCBs and on the schematics helped most of all. Working on the first crossover, I went forward logically, one step at a time and it eventually worked out. Wound up replacing all the capacitors, about 90% of the resistors and replaced or unwound to lower values about 95% of the inductors. Otherwise, most parts were direct replacements, swapping old parts with new value parts. Also noticed some differences in "on and off PCB" mounted inductors, but I made some judgments and sorted them out too. After several days of working very carefully, I finished the first crossover and tested it successfully the first time, much to my relief and joy. Doing what I did on the first one, the second crossover upgrade was only a two day job. Wound up costing about $200 or so, which was probably much cheaper than buying replacement 250Ti crossovers, if they could even be found at all. I've been an electronics hobbyist (parts swapper) most of my life, but this crossover upgrade was a real challenge and a kick to have pulled it off successfully. Also I get to enjoy my work every day when I listen to these wonderful speakers.

  3. #3
    Senior Member DavidF's Avatar
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    I wasn't one who helped with guidance but it's nice to hear from members who have put such advice to good use.
    David F
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  4. #4
    Junior Member LarryM's Avatar
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    What a 250ti crossover looks like

    I helped a bit with this upgrade, but he really had the work done before I made contact. Most of my help was with some pictures of an original 250ti crossover as I had at one time. About 9 years ago, I upgraded my L250 which already had the ti kit installed. The project was to upgrade the ti kit to CC'd version.

    Included here are a couple of pictures of the original 250ti crossover, in case someone is interested in converting their L250. Although with the difficulty of obtaining the 104H and 044ti, I assume few would even make the attempt. It should be noted the 250ti uses the same PCB as the L250. It is just populated with different components and L1, L2 are removed. The masonite board is obviously quite different for the two versions. Since my masonite board was already a 250ti, there was no need to remove any of the 10 watt resistors, which a ti change would require. One could easily destroy the board trying to get them off. Someone else may know how to do this. Maybe it would be better to just leave the R's in place and glue the needed new ones on top and rewire the rest. JBL also compromised by mounting the air-core coils right next to each other. Better to move them apart off-board, if possible. Be sure to mount the coils with stainless or real brass screws, not the cheap brass plated steel or else you will add unwanted inductance to the coil. When buying hardware, take a magnet to the store with you. There should be no attaction.

  5. #5
    Junior Member LarryM's Avatar
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    250ti crossover
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    Nice Work guys!


  7. #7
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    Hello;
    I am about to make the plunge, and upgrade my 250ti crossovers. I have collected a ton of info from the pages on the forum. I have decided to follow your model. one question so far. There is what appears to be a capacitor in your photo, just below the r4 7.5 resistor that is not present on the original diagraham. can you detail what/why its there. I intend to start ordering parts for this mod
    don't want to leave anything out.
    Thanks in advance for any info or advice that you are willing to share.

    David

  8. #8
    Junior Member
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    Hello;
    I am about to make the plunge, and upgrade my 250ti crossovers. I have collected a ton of info from the pages on the forum. I have decided to follow your model. one question so far. There is what appears to be a capacitor in your photo, just below the r4 7.5 resistor that is not present on the original diagraham. can you detail what/why its there. I intend to start ordering parts for this mod
    don't want to leave anything out.
    Thanks in advance for any info or advice that you are willing to share.

    David

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