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Thread: Improving The JBL L 7

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    Improving The JBL L 7

    The JBL L 7's I now own are my second pair.
    The first pair did not work out for me.
    This second pair sounded a LOT better.
    I also own B&W Matrix 801's as a reference speaker.
    I heard problems in this second pair of L 7's immediately.
    Cat Stevens and Bob Seeger revealed what I THOUGHT to be insufficient damping material behind the drivers.
    I about drove myself crazy adding, removing, and trying various amounts and types of damping materials.

    After speaking with the ex JBL engineer who designed these speakers, I realized the problem is NOT in the upper two cone drivers.
    What I was hearing is the upper range of the side mounted woofers!

    He told me these should be a generous amount of fiberglass behind the side mounted woofers, and to check to see if it was installed per his specs.
    Sure enough, it was NOT!

    So, I pulled out the totally useless 1/2 inch fiberglass sheet the factory installed.

    In it's place, I placed the 2 inches of fiberglass, being careful NOT to block the port.
    I listened again, better, much better, but STILL I could hear the upper range of the driver.

    So, I undid the woofers again, and stuffed some additional fiberglass up into the top of the cabinet.
    There is a hole leading from the woofer chamber into the top of the cabinet.
    I LOOSELY filled this hole with some additional fiberglass.
    This did the trick!

    No more Chesty sound on Cat Stevens or Bob Seeger.

    Are the L 7's a B&W Matrix 801 ?
    Not in this lifetime, but I like them a lot still.

    The bass did not seem to suffer by adding the extra fiberglass.
    If anything, it got tighter.

    Once this woody, chesty sound is gone from the L 7, they really open up.

    Imaging is FAR better, and it just plain sounds better, top to bottom.

    If YOU own L 7's, you NEED to CHECK the damping behind ALL drivers!

    Mine were ALL wrong, according to what the designer of these speakers TOLD them he wanted.

    Just a couple of hours time, and you can have your L 7's sounding the way the designer INTENDED them to sound.

  2. #2
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    Chris

    You got pictures of the procedure?

  3. #3
    Registered User MJC's Avatar
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    When I was building my subs, I stuffed the boxes with 3 1/2" fiberglass batts, all around, except the baffle.
    The same with my L212s, stuffed the mid-bass enclosure almost to the max and the mid-range enclosure as well. The insulation also increases the virtual volume of the boxes.

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