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Thread: woofer impedance folded horns

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    woofer impedance folded horns

    I have 2 "K" type folded horns with JBL 2205 woofers rated at 16ohms.
    I understand that the woofers should be 3.2ohms. Can I place resistors across the woofer terminals ( Pos. to Neg.) to lower the impedance? What values on the resistors do I need?

    I am using the LX-5 network ,8ohms, and the 2440 drivers with horn and lens assembly. The LX-5 actually measures
    12.5ohms.
    Last edited by Esoteric; 08-14-2007 at 01:55 PM. Reason: Addded crossover information.

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    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.
    Harvey "Hifi" Gerst
    ("Hifi" was my nickname at JBL.)

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    foldeed horns

    Quote Originally Posted by grumpy View Post
    Why is that?
    Hal Cox suggested that impedance and I think Klipsch used 3.2 drivers.

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    RIP 2010 scott fitlin's Avatar
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    I think the impedance of the original woofers used was a 4ohm woofer, as 3.2 ohms is the DC resistance, not the impedance. Many 4 ohm woofers of the past would read 3.2 ohms on a meter.
    scottyj

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    folded horns

    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.
    Thank you, Harvey for your suggestions.

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    folded horns

    Quote Originally Posted by scott fitlin View Post
    I think the impedance of the original woofers used was a 4ohm woofer, as 3.2 ohms is the DC resistance, not the impedance. Many 4 ohm woofers of the past would read 3.2 ohms on a meter.
    You're right. My mistake. The woofers were 4ohms. I don't understand why
    because my woofers blend nicely with the 2440s, but I just wondered what I was missing if anything. The curse of us hi-fi nuts!

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    Yeah, but if the crossover networks were designed to see a 4 ohm impedance, you arent getting the correct performance using 16 ohm coils.
    scottyj

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    folded horns

    Quote Originally Posted by scott fitlin View Post
    Yeah, but if the crossover networks were designed to see a 4 ohm impedance, you arent getting the correct performance using 16 ohm coils.
    I understand that, but the crossovers (LX-5s) actually measure 12.5 ohms and not a bad match for the woofers. I want to know why JBL used a 4 ohm woofer in the Hartsfield and Paragons with 8-16 ohms mid and hi freq.drivers which is what Klipsch did. My speakers are very similar to the Hartsfields.

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    folded horns

    Quote Originally Posted by grumpy View Post
    I could be mistaken, but wasn't the LX-5 expecting nominal 16 ohm drivers?
    (like LE15A, or was there more than one LX-5 version?)
    Horn loading the 2205 might raise the driver's impedance some... which
    would tend to lower the crossover for the bass driver (only)... perhaps
    making a hole where the K-horn is already running out of steam (400-500Hz)

    ... that's about all I can think of without available measurements with
    respect to frequency (impedance and/or amplitude).

    Bottom line... if you like what you're hearing, why poke at it?
    (OK... I would too )

    Edit: why 4ohm drivers in horn loaded enclosures?
    Some interesting reading:
    http://www.volvotreter.de/khorn.htm



    -grumpy
    There were 8 and 16 ohm versions of the LX-5. I have the 8 ohm unit. Thanks for the link, it answers my question. Nick

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    Quote Originally Posted by Esoteric View Post
    I understand that, but the crossovers (LX-5s) actually measure 12.5 ohms and not a bad match for the woofers. I want to know why JBL used a 4 ohm woofer in the Hartsfield and Paragons with 8-16 ohms mid and hi freq.drivers which is what Klipsch did. My speakers are very similar to the Hartsfields.
    Whoa, back the wagon up there, sonny. When exactly did we ever put 4 ohm woofers in Hartsfields? I don't remember that during my time at JBL, and I was the guy putting the speakers in them and testing them.
    Harvey "Hifi" Gerst
    ("Hifi" was my nickname at JBL.)

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    Senior Moment Member Oldmics's Avatar
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    Yeah,Think ya Got Some Incorrect Information There

    Hartsfields used 16 ohm woofers,16 ohm on the 375 drivers and 16 ohm on the tweeters that were so equipted.

    Same with the Paragon drivers.

    Oldmics

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    Quote Originally Posted by Harvey Gerst View Post
    Whoa, back the wagon up there, sonny. When exactly did we ever put 4 ohm woofers in Hartsfields? I don't remember that during my time at JBL, and I was the guy putting the speakers in them and testing them.
    So what kind of speakers did you put in the Hartsfields and Paragons?

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    Quote Originally Posted by RKLee View Post
    So what kind of speakers did you put in the Hartsfields and Paragons?
    When we started putting out Hartsfields and Paragons, they came standard with 150-4C's in both. Even with the first "coffin-back" Hartsfields, they had 150-4C's. After Ed May and Bart Locanthi came up with the LE-15, we switched to those instead.

    Most of the Hartsfields were made during the Fletcher Drive years. The coffin-back Hartsfield was designed by Bill Burton and Bart Locanthi while we were still on Fletcher Drive. We started thinking about stereo only during the last year or so at Fletcher Drive, but it became more serious when we moved to Casitas.

    The Paragons were all from the Casitas years. Ed May didn't come on board till after we moved to Casitas, so no LE-15's were even designed until well after our move from Fletcher Drive. I remember working on the first Paragon prototype. That's the only time I met Col. Richard Ranger.
    Harvey "Hifi" Gerst
    ("Hifi" was my nickname at JBL.)

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    [quote=Harvey Gerst;181388]When we started putting out Hartsfields and Paragons, they came standard with 150-4C's in both. Even with the first "coffin-back" Hartsfields, they had 150-4C's. After Ed May and Bart Locanthi came up with the LE-15, we switched to those instead.

    quote]


    Harvey,

    sorry my English is very bad. Do I have correctly understood also in the Hartsfield the LE15 was used?

    regards
    juergen

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    [quote=rs237;181389]
    Quote Originally Posted by Harvey Gerst View Post
    When we started putting out Hartsfields and Paragons, they came standard with 150-4C's in both. Even with the first "coffin-back" Hartsfields, they had 150-4C's. After Ed May and Bart Locanthi came up with the LE-15, we switched to those instead.

    quote]


    Harvey,

    sorry my English is very bad. Do I have correctly understood also in the Hartsfield the LE15 was used?

    regards
    juergen
    We were making very few Hartsfields by the time the LE-15 came out, but yes, I think I recall putting the LE-15 in some of the last Hartsfields made. I may be wrong, but catalogs from that period (around 1965) should have it right.
    Harvey "Hifi" Gerst
    ("Hifi" was my nickname at JBL.)

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