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Thread: Group Delayed Speakers, anyone?

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    Registered User MJC's Avatar
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    Group Delayed Speakers, anyone?

    Hi all happy holidays.
    This month I had the pleasure of auditioning a pair of speakers that were designed by a local electrical enginneer. They are of the MTM type, that has a time aligned baffle. The tweeter is set back 3/4" from the mids.

    But the main thing about these speakers is the crossovers. He calls it Group Delayed. Each driver has its own crossover board that is mounted right next to the driver. He spects all parts to tight tolerances. And all the leads and wires, including the wires running from the boards to the drivers are cut to precise lengths.
    The result is a pair of speakers that image beautifully, better than my mirrored L212s, with very detailed highs and a quick mid-bass down to 45~40htz.
    But its the depth of the soundstage that I've never encountered before. At least 10~15' deep.
    He told me that one guy who has heard them said "that they sound better than his $22K speakers."
    He had a local cabinet shop build 12 boxes, from his design, which are already sold. Even though he is still in the process of building the other 10 crossovers. He said that they are very time consumming. I forget the brand of the tweeter, but I think the 6" mids are Focal.

    But this enginneer's main income is from designing analyzers for coffee roasting(among others), that he said all roasters use. I also tried his coffee(mohca expresso), every bit as good as his speakers.

    The one thing I forgot to ask was how much he was selling them for. The next time I go over to his shop to buy some coffee, I'll take some of my cds and ask how much the speakers go for.

  2. #2
    Member whej4312's Avatar
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    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...
    James B. Lansing, David Hafler.
    Saul Marantz, Avery Fisher.
    Edgar Vilchur, Henry Kloss.
    David Day, Bob Carver.
    Stan Warren, Mark Levinson.
    Paul McGowan, Edmund May.
    Visionaries....




  3. #3
    Senior Member Ian Mackenzie's Avatar
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    [QUOTE=MJC]Hi all happy holidays.
    But the main thing about these speakers is the crossovers. He calls it Group Delayed. Each driver has its own crossover board that is mounted right next to the driver. He spects all parts to tight tolerances. And all the leads and wires, including the wires running from the boards to the drivers are cut to precise lengths.

    ]

    Sorry I think he's pulling you leg.

    For the real facts do a search for Siegfried Linkwitz

  4. #4
    Member whej4312's Avatar
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    [QUOTE=Ian Mackenzie]
    Quote Originally Posted by MJC
    Hi all happy holidays.
    But the main thing about these speakers is the crossovers. He calls it Group Delayed. Each driver has its own crossover board that is mounted right next to the driver. He spects all parts to tight tolerances. And all the leads and wires, including the wires running from the boards to the drivers are cut to precise lengths.

    For the real facts do a search for Siegfried Linkwitz
    Time alignment is critical in any application. Ian do you remember the L300? Everest? Why were the faces of the cabinets back 5 to 15 degrees? Siegfreid Linkwitz essentially came up with a different way to document and change phase anomolies at the crossover points, hence Linkwitz-Riley 2nd, 3rd, and 4th order constant phase and null phase networks. I have never heard a very good Linkwitz passive design. I have indeed heard many successful Linkwitz odd and even order Electronic Crossovers though. Any old AES journals have tons of info on their work. While this guy claims group delay, I really wonder where the delay is. If the tweeter is physically stepped back, than what does that do to lobing at the x-over point. Sound's like this guy is playing at phase trickery to make his sound stage bloom!!

    Want bloom? Buy Toobes!!
    James B. Lansing, David Hafler.
    Saul Marantz, Avery Fisher.
    Edgar Vilchur, Henry Kloss.
    David Day, Bob Carver.
    Stan Warren, Mark Levinson.
    Paul McGowan, Edmund May.
    Visionaries....




  5. #5
    Administrator Robh3606's Avatar
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    "Time alignment is critical in any application. Ian do you remember the L300? Everest? Why were the faces of the cabinets back 5 to 15 degrees?"

    Take a look at the L300 brochure on the site. The 4333 and L300 both used a very long midrange horn. There is no way that an angled baffle would be able to compensate for the path length diferences between the woofer, compresion driver and the slot. The only reason I can see why was to help the 077 because of the limited vertical dispersion.

    Rob

  6. #6
    Member whej4312's Avatar
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    Quote Originally Posted by Robh3606
    "The 4333 and L300 both used a very long midrange horn. There is no way that an angled baffle would be able to compensate for the path length diferences between the woofer, compresion driver and the slot. The only reason I can see why was to help the 077 because of the limited vertical dispersion.

    Rob
    Are you sure? I wonder what the polar pattern of the 300/4333 look's like at their crossover points? I agree that the 077 slottie might be one of the reasons, or it could be even simpler. Because who would put L300's on a pair of stands!! Maybe JBL just did it to aid in deep shag dispersion!! LOL!!
    James B. Lansing, David Hafler.
    Saul Marantz, Avery Fisher.
    Edgar Vilchur, Henry Kloss.
    David Day, Bob Carver.
    Stan Warren, Mark Levinson.
    Paul McGowan, Edmund May.
    Visionaries....




  7. #7
    Administrator Robh3606's Avatar
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    Well take a look see what you think.

    http://www.lansingheritage.org/image...l300/page3.jpg
    Rob

  8. #8
    Senior Member Ian Mackenzie's Avatar
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    I think you may have your magnification turned up too high.

    I was referring to the wires being cut the exact same length.

    As to the rest of it I really do not have time to debate theoretical issues about Linkwitz crossover design or why JBL do and didn't do certain things with their products.

    You can be assured however they are both classic examples of sound engineering practise with respect to real world considerations.

    Ian

  9. #9
    Senior Member Ian Mackenzie's Avatar
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    [QUOTE=whej4312]Time alignment is critical in any application. Ian do you remember the L300? Everest? Why were the faces of the cabinets back 5 to 15 degrees?

    QUOTE]

    Pigs arse,

    They (L300) were angled slightly back due to the limited vertical dispersion of the drivers.

    Any idiot could tell you that.

    There's no fancy theoretical rocket science with this stuff

    If your gonna bullshit at least do it properly and check your references...that way won't notice so much.

    Ian:o

  10. #10
    Administrator Mr. Widget's Avatar
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    Ian, calm down boy.

    Group Delay is a BS answer. I really don't doubt that the coffee engineer is putting some good practical design engineering into the mix and quite likely is designing a speaker that images better than most JBLs. Many people have.

    As for precise wire length... other than to maintain specific resistance goals, there is no reason (that I know of) to jump through those hoops. In the design of microwave communications equipment wire length and even shape make a difference, but last time I checked we were listening to Hz-KHz not GHz.

    Many designers will focus a bit too much in one area or another. In the halls of audio marketing they turn up the BS factor to 11, but I assume this guy is still a believer and not a snake oil salesman.

    Please do find out what components he is using as well as crossover topology and price... a photo or two would also be nice.

    I would love to see what he is up to.

    Widget

    BTW: I agree with whej4312. I think your imaging would improve dramatically if your baffles were treated or narrowed to 8", but I have mentioned this before.

  11. #11
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    Quote Originally Posted by Mr. Widget
    BTW: I agree with whej4312. I think your imaging would improve dramatically if your baffles were treated or narrowed to 8", but I have mentioned this before.
    Just build some mini-L250/250Ti pyramids for the 8-inch 3-ways.

  12. #12
    Moderator / Treasurer/Marketplace Czar boputnam's Avatar
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    Dammit, Giskard!!

    Doods...

    Where were you guys?? When I read the original post I just shrugged it off and decided I hadn't sufficient time. Plus, unless we can post directly with Mr. Grounds, debating what was heard and seen would be fairly unproductive.

    It would be nice to get some photos and descriptions from Mr. Grounds himself, so that he can explain his design.

    'nuff said.
    bo

    "Indeed, not!!"

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    Senior Moment Member Oldmics's Avatar
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    Mr. Grounds Himself

    Thats too funny.

    Perhaps a Columbian connection.

    Oldmics

  14. #14
    RIP 2011 Zilch's Avatar
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    Time alignment?

    Quote Originally Posted by whej4312
    Why were the faces of the cabinets back 5 to 15 degrees?
    Because it looked cool, most likely. It also matched the profile of the new Bob's Big Boy counter that had just opened down the street, where everybody ate lunch daily.

    I'm certainly not ABOUT to argue that L200 or B460 are "Time aligned," either, nope.

    Or that we all love the "West Coast" sound....

  15. #15
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by MJC
    But its the depth of the soundstage that I've never encountered before. At least 10~15' deep.
    Electronics and source material has a lot to do with this too. Most CDs are rather flat and most moderately priced amps, preamps etc. tend to flatten the image as well.

    What type of source material and electronics was "Mr. Grounds" using?

    Widget

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