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Thread: woofer impedance folded horns

  1. #31
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    Quote Originally Posted by glen View Post
    from the Hartsfield article on this site:
    http://www.audioheritage.org/html/pr...hartsfield.htm
    "The logic of stuffing a $25 driver into a $300 enclosure was questionable at best and was never a marketing success. This option was dropped within two years. "
    © 2000 Don McRitchie


    But I wonder if that D208 option might have been influenced by the Lowther loudspeaker single-driver philosophy and designs that were popular with hobbyists in England. The D208 would have been the LE8T of it's time, and there are still plenty who still think the LE8T is the best option available.

    Around the same time the Hartsfield was introduced Lowthers were being used in large rear-loaded folded horn cabinets. The TP1 London enclosure, introduced in the 50's and still being made, is a big front and rear-loaded corner horn, but at 39x31x23 inches (102x80x60 cm) not quite as big as a Hartsfield.

    Maybe someone at JBL thought the D208/D216 was special enough to spark a wave of interest similar to the Lowther popularity that is still going strong today.

    Has anyone ever heard a D208/D216 in a Hartsfield cabinet?
    Believe it or not, I had a pair of Hartsfields for a while with Lowther's in them and they did sound pretty damn impressive. The 208 adapter kit was a curved smaller wood horn arrangement, that sat where the lens goes, and arched down to the woofer opening. I'll try to draw something up today as to what it looked like.

  2. #32
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    Quote Originally Posted by Harvey Gerst View Post
    Uh, that's not a great idea; the resistors would get most of the power and it would just be radiated as heat.

    The right answer to the resistor problem would be adding a 4 Ohm resistor in parallel across the 16 Ohm speaker to achieve a 3.2 Ohm load, but it's not the right solution.

    The correct solution is to use a different amp that can properly drive the woofer, or recone the speaker to the desired impedance.
    If your current amp is able to drive the speaker/enclosure to a level you are happy with then there is no reason for a new amp. Now the only question is does the crossover match the woofer. If it doesnt it can be modified or replaced. If it is looking for 4ohms and sees 16 it will cross much higher. This may or may not be audible as you undoubtedly have a lot of mechanical roll off as well.

    It's also possible that it is so efficient that you are using so little power that you actually could parallel it with a power resistor but I would make sure that I had a problem before I started fixing it.

  3. #33
    Senior Member rs237's Avatar
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    Quote Originally Posted by glen View Post
    Has anyone ever heard a D208/D216 in a Hartsfield cabinet?

    unfortunately not. As Fullrange fan I would try it gladly. Unfortunate those the plans of the old Hartsfield are not available.

    regards
    juergen

  4. #34
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    Very strange to realize I may be the only person on the planet to have heard the Lowthers in the old Hartsfield cabs. I don't remember installing any 8" speaker kits in the Hartsfields while I worked there. We may have built a few, but it would have been a damn few.

    The other "weird" system I had was a Metragon with Janzen electrostatic tweeter and their woofers installed. What the "weird" part is that the cabinet shop actually made the Metragon with the Janzen cutouts for me; the only time I think they built something for non-JBL components. I damn near got fired because of it. Bill Thomas actually had to step in and settle the dispute it caused.

  5. #35
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    The 208 "Hartsfield kit" used 1/4" plywood as I recall for the horn part, while the box and 15" opening adapter was 1/2" thick. Excuse the crude drawing but the 208 "Hartsfield kit" kinda looked like this:
    Attached Images Attached Images  

  6. #36
    RIP 2011 Zilch's Avatar
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    There is no mystery here as to why the Hartsfield was built the way it was. Look at the independent claims of the patent, 1, 4, 7, and 10.

    http://www.audioheritage.org/html/pr...hartsfield.htm

  7. #37
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    Quote Originally Posted by Zilch View Post
    There is no mystery here as to why the Hartsfield was built the way it was. Look at the independent claims of the patent, 1, 4, 7, and 10.

    http://www.audioheritage.org/html/pr...hartsfield.htm
    Damn, you mean I didn't hafta do the drawing?

  8. #38
    RIP 2011 Zilch's Avatar
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    It was a test, Harvey.

    [And you passed, obviously.... ]

  9. #39
    Senior Member louped garouv's Avatar
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    that's awesome....


  10. #40
    Senior Member glen's Avatar
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    Quote Originally Posted by Harvey Gerst View Post
    The other "weird" system I had was a Metragon with Janzen electrostatic tweeter and their woofers installed. What the "weird" part is that the cabinet shop actually made the Metragon with the Janzen cutouts for me; the only time I think they built something for non-JBL components. I damn near got fired because of it. Bill Thomas actually had to step in and settle the dispute it caused.
    What the hell!
    Hey Harvey, you gotta give us more details on this story,
    sounds good enough to be a whole new thread!
    Anybody who came accross that cabinet would have been shaking their head at the weird customization done to a perfectly good Metregon system
    glen

    "Make it sound like dinosaurs eating cars"
    - Nick Lowe, while producing Elvis Costello

  11. #41
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    Quote Originally Posted by glen View Post
    What the hell!
    Hey Harvey, you gotta give us more details on this story,
    sounds good enough to be a whole new thread!
    Anybody who came across that cabinet would have been shaking their head at the weird customization done to a perfectly good Metragon system
    Yeah, but it's probably not worth a whole thread. George Augspurger and I were always putting together weird stuff, and I was impressed with the clarity of these new electrostatic tweeter panels that I heard at one of the Hi-Fi shows. What I wasn't impressed with was the dispersion. There was none.

    Soooo, I reasoned, what if I dump this stuff into a Metragon to give me the dispersion? I bought one, using my employee discount and gave the cabinet shop the layout I wanted for the baffle boards. When the paperwork came across our sales dept. desk, the shit hit the fan.

    "The discount is to encourage JBL employees to buy JBL systems; you can't put other peoples components in there." Well, I didn't take that laying down (I was very pushy in my youth).

    Ray Pepe and I argued, but we were both unmovable. Finally, Bill Thomas came in and settled the argument - in my favor. It was a kickass sounding system.

  12. #42
    RIP 2010 scott fitlin's Avatar
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    Hey, thats a great story.

    scottyj

  13. #43
    Senior Member glen's Avatar
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    Harvey Gerst Loudspeker Freakshow

    Quote Originally Posted by Harvey Gerst View Post
    Yeah, but it's probably not worth a whole thread. George Augspurger and I were always putting together weird stuff . . .
    Sure sounds like an interesting thread to me, wonder what else you had along with the Jantzen powered Metregon and Lowthers in Hartsfield cabinets.

    What happened to those oddball systems?
    Do you still have any of them?
    glen

    "Make it sound like dinosaurs eating cars"
    - Nick Lowe, while producing Elvis Costello

  14. #44
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    Quote Originally Posted by glen View Post
    Sure sounds like an interesting thread to me, wonder what else you had along with the Jantzen powered Metregon and Lowthers in Hartsfield cabinets.

    What happened to those oddball systems?
    Do you still have any of them?
    Nope, they're all long gone. I had a couple of 300Hz horns for 175 drivers that I found in the back room at JBL. They were about 3 feet deep by 3 feet wide by maybe 10 inches tall. Somebody told me they were made for Bolt, Baranck?, & Neuman, or possible Ampex.

    Other than the big JBL system (in our Studio A) that Ed May built for himself, all the JBL's I still have are stock stuff.

  15. #45
    RIP 2010 scott fitlin's Avatar
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    Quote Originally Posted by Harvey Gerst View Post
    Nope, they're all long gone. I had a couple of 300Hz horns for 175 drivers that I found in the back room at JBL. They were about 3 feet deep by 3 feet wide by maybe 10 inches tall. Somebody told me they were made for Bolt, Baranck?, & Neuman, or possible Ampex.

    Other than the big JBL system (in our Studio A) that Ed May built for himself, all the JBL's I still have are stock stuff.
    No one off JBL designs?

    No things that would have been fantastic but never made it to production because they would cost too much to produce?

    JBL had to have a few things no one knows about! Not even 1?

    scottyj

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