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Thread: Group Delayed Speakers, anyone?

  1. #31
    Webmaster Don McRitchie's Avatar
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    Quote Originally Posted by Robh3606
    Hello Don

    Have you ever read the Stereophille review on the L250's?? I would love to scan and post it to get owner reactions. Let's just say it has a few twists and is not that favorable.

    Rob
    I never have. I would love to get the chance.

    Don

  2. #32
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    John,

    Great pickup.

    Glad to see you are enjoying your revived JBL's.

    Would be nice if you can post us a closer look.


    Ian

  3. #33
    MJC
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    L212s side ways

    Quote Originally Posted by Ian Mackenzie
    John,

    Great pickup.

    Glad to see you are enjoying your revived JBL's.

    Would be nice if you can post us a closer look.


    Ian
    Will do.
    I had a thought the other day, while listening to just the mirrored pair and the 2 sub1500s, that I have another pair of boxes I built two years ago, not being used. Reworking the boxes by leaving the 8" driver holes where they are, on the wide face, pluging up the holes for the 066s and le5-9s and cutting out new holes on one end, at the same elevation as the pluged holes.
    This configuation would simular to the Infinity Preludes, speakers that I auditioned in 2000, and thought were every bit as neutral sounding as the L212s. Just to see(hear) what improvement, if any, would take place.
    Of coarse the Preludes come with a heathy price tag of over $12k for 5.2 system.

    whej4312
    btw, have you ever noticed that the size of the baffle of the Performance Series towers and driver placement is about identical to the L212s? And in the brochure for the L212 it sez that "the width of the cabinet is designed to create a front baffle surface that is effectively infinite for the high frequency radiator."
    Although off setting the drivers two inches in has produced an even better soundstage, a better "center channel" in stereo playback.

    So I guess at JBL, what goes around, comes around. Because here we are a quarter of a century later, 1977~2002 (the years that these two speaker systems were debuted) and the biggest difference in the L212 and Performance Series is what the drivers are made from, with the PS being Titanium.
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  4. #34
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    Nice work John,

    Would be interesting to hear your impressions with the spare box

    I wish I had some spare JBL drivers to tee up a L212. Eventually I plan to built a ''good'' 4 way electronic crossover to play around with these concepts.

    Ian

  5. #35
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    Quote Originally Posted by MJC
    .

    whej4312

    So I guess at JBL, what goes around, comes around. Because here we are a quarter of a century later, 1977~2002 (the years that these two speaker systems were debuted) and the biggest difference in the L212 and Performance Series is what the drivers are made from, with the PS being Titanium.
    Yes it does, Beautifully put.

  6. #36
    MJC
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    Quote Originally Posted by Ian Mackenzie
    Nice work John,

    Would be interesting to hear your impressions with the spare box

    I wish I had some spare JBL drivers to tee up a L212. Eventually I plan to built a ''good'' 4 way electronic crossover to play around with these concepts.

    Ian
    Thanks, finding the 066s and the le5-9/2105 are easy, its the 112A that took most of 2 years to get 4 of them, being they were only used in the L212.
    I still haven't gotten around to buying some .005uF polystyrene caps to use as bypass caps for the 066s, but I did install polyproplene bypass caps for the 2105 and 112A.

  7. #37
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    Lsr28

    I am interested in your high regard for the LSR28. I would like to see if anyone else here has a similarly high opinion of the LSR28 or LSR6328. I don't have the reference point of all those other JBLs to compare them to. Yes, I know this is an old post...

    Quote Originally Posted by whej4312 View Post
    MTM designs have been around for years. It's just that Joe DiAppolito decided to patent his version. As far as Real Group delay designs, many of your european high-end manufacturers as well as American high-enders use very close tolerances in both driver topology and in the execution, placement and design of the network. Here in Colorado, Avalon Acoustics claim's that they can control off axis group delay and distortion nodes by A; physical placement of the Drive Units on the baffle plane. Augmenting the physical size of the baffle, controlling unwanted resonant points within the confines of the cabinet, and B; Controlling crossover and acoustic anomolies in the crossover with regards to the drivers inherant acoustical/electrical properties within the cabinet design. I have many friend's as well as myself that have experimented with wire types, wire lengths, coils, caps, and resistors to obtain a certain sound. Trust me, these things matter enormously. When you get a chance to hear these speakers again, one thing to look for is a lack of vertical dispersion. MTM's (Symmetrical Array) generally have stellar horizontal charictaristics but lack a true vertical soundstage.They sound closed-in and lack placement of the image vertically. In your L-212's case, driver placement on the baffle plane is a big problem. The baffle is much to wide to make the L-212's behave like a point source. Damping the face acoustically helps a ton. I have a few tricks on that idea. Finally, while we all know that JBL can and does build some of the most remarkable drivers out there, their overall cabinet designs and crossover execution leave a lot to be desired. In my opinion the closest JBL has ever gotten to a real world high-end worthy loudspeaker is, K-2, LSR28, and more importantly the Century Gold. But if you look at the networks or cabinet design in any of them, they still leave me wondering why. Why James B. Lansing Sound Inc. Can't build a speaker that would flatten the industry much like or beloved L-100 and 4310. As simple as they were, they did, to this day what no one has. Sell well, and sell often. Plus that patented, trademarked, and elusive WestCoast Sound we all love. Speed baby, It's that simple...

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