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Thread: 130a, 175DLH crossover info... please?

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  1. #1
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    130a, 175DLH crossover info... please?

    I wish to build a pair of JBL speakers, in an 8cu. ft. bass reflex enclosure, (JBL design) using a 130a 8Ohm bass and 175DLH 16Ohm horn, driver, lens. I do not, however, have the proper N1200 crossover. I do have a pair of 3120 Professional crossovers. Would these be a drop in substitution?

    I'm guessing that they would work just fine. But then, I really don't know anything about crossover design math.

    What can I expect? Thank you.

    Steve

    "I'm OK with what I know that I don't know. It's what I don't know that I don't know that's the problem."

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    Quote Originally Posted by Stevedel View Post
    I wish to build a pair of JBL speakers, in an 8cu. ft. bass reflex enclosure, (JBL design) using a 130a 8Ohm bass and 175DLH 16Ohm horn, driver, lens. I do not, however, have the proper N1200 crossover. I do have a pair of 3120 Professional crossovers. Would these be a drop in substitution?

    I'm guessing that they would work just fine. But then, I really don't know anything about crossover design math.

    What can I expect? Thank you.

    Steve

    "I'm OK with what I know that I don't know. It's what I don't know that I don't know that's the problem."

    I'm on my B/U computer ( so I can't do the comparison for you ) but I recommend you use google to find the published schematics for the two computers ( then compare them for any differences between the values of the LC components ).

    That'll certainly help further the conversation in a meaningful manner.


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    Senior Member grumpy's Avatar
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    A quick check of the schematics would seem to indicate functional equivalence.
    Good to doublecheck though.

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    Thanks for taking the time to respond, Grumpy, Earl.

    I think that there is a little more here than meets the eye. I've seen the schematics but don't know enough to compare them. Also, the old 130a, 175DLH and N1200 are for 16 Ohm components. The newer components (LE175DLH, 130a) are 8 Ohm.

    To further confuse me, the 3120 is listed for a LF driver of 8-12 Ohms and HF of 12-16 Ohms.

    At least, with further investigation, I'm beginning to know what I don't know so thanks for that.

    Maybe someone can recommend a good book on crossover design. I'll make use of that and get out the HP50g calculator like I know what I'm doing. My math education was BC (Before Calculator) so I'll have a bit of a learning curve. But then, I always think that things are a bit more complicated than they really are.

    Perhaps I should use the 3120 crossovers and play with the resistor values for the best sound.

    I'd best think this through a little more.

  5. #5
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    Quote Originally Posted by Stevedel View Post
    Thanks for taking the time to respond, Grumpy, Earl.

    I think that there is a little more here than meets the eye. I've seen the schematics but don't know enough to compare them. Also, the old 130a, 175DLH and N1200 are for 16 Ohm components. The newer components (LE175DLH, 130a) are 8 Ohm.

    To further confuse me, the 3120 is listed for a LF driver of 8-12 Ohms and HF of 12-16 Ohms.

    At least, with further investigation, I'm beginning to know what I don't know so thanks for that.

    Maybe someone can recommend a good book on crossover design. I'll make use of that and get out the HP50g calculator like I know what I'm doing. My math education was BC (Before Calculator) so I'll have a bit of a learning curve. But then, I always think that things are a bit more complicated than they really are.

    Perhaps I should use the 3120 crossovers and play with the resistor values for the best sound.

    I'd best think this through a little more.
    You might enjoy the old Cohen text from the '60s. It's got all the basics in terms of math, schematics, charts that explain how this stuff actually works. All the old vintage systems of the day as well. Today's computer based manuals are not the best in terms of physics, etc., they do all the work for you; based on models which, of course, are only models. Anyway, Abraham B. Cohen, Hi Fi Loudspeakers and Enclosures. Amazon? But, it's a good hobby - and those old 3120s are not all bad "starter" units. Can modify to taste, etc.

  6. #6
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    Thank you, Mannermusic.

    Found a copy on Amazon for a good price. It's on it's way.

    Through sleet and snow and all that.

    Regards, Steve

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