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Thread: Tractrix Horn Help

  1. #1
    Senior Member Sootshe's Avatar
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    Tractrix Horn Help

    I'm considering a timber tractrix horn with a GPA 399. It will have an Fc of 250Hz & the mouth dimensions will be 23" wide X 9" high x 16.87" deep with a 1" motorboard. It will be similar to the attached pic.

    There's plenty of info to determine the lowest frequency that the proposed size horn will go to, the program used to generate the dimensions will calculate this & many other things. My problem is determining how high this horn will go to.

    Would anyone know if it will go up to the upper limit of the driver? That is, to 15K?
    Thanks,
    John
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  2. #2
    Maron Horonzakz
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    Yes I,m famallier with that Martinelli horn,,,And its owner,, With the proper driver it will go to 18K

  3. #3
    Senior Member Lee in Montreal's Avatar
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    Quote Originally Posted by Maron Horonzakz View Post
    Yes I,m famallier with that Martinelli horn,,,And its owner,, With the proper driver it will go to 18K
    Interesting. And what would that proper driver be? Anything JBL? TIA.

  4. #4
    Senior Member Sootshe's Avatar
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    Quote Originally Posted by Maron Horonzakz View Post
    Yes I,m famallier with that Martinelli horn,,,And its owner,, With the proper driver it will go to 18K
    To clarify, the picture of the horn is not mine, I just used it as an example of what it will look like.
    Would one similar to this, with the specs given above, go all the way to the limit of the 399, that is, to 15K?

    I've read some reports that horns of this type sometimes only go to 6-7K & therefore will limit the frequency range of the driver, regardless of how high the driver goes.

    Thanks,
    John

  5. #5
    Maron Horonzakz
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    Not so,,,,But the polor response would suffer,,Verticle Vs Horizontal

  6. #6
    Senior Member spkrman57's Avatar
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    Great Plains 399 driver is 1.3875" not 1"

    That will change the math somewhat.

    Ron sends...
    JBL Pro for home use!

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    Senior Member stephane RAME's Avatar
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    Club double 16"
    "Laissez les Bons Temps Rouler"

  8. #8
    Senior Member Lee in Montreal's Avatar
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    Quote Originally Posted by stephane RAME View Post
    Thanks for the link Steph.

    "Frequency Response: 500 Hz - 15 kHz at rated power."

    If the above rating doesn't include "within X db" it is a meaningless info. It might very well be 800Hz- 8Khz within 3db

    Manufacturers usually include a grah to back-up their claim.

  9. #9
    Senior Member stephane RAME's Avatar
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    Club double 16"
    "Laissez les Bons Temps Rouler"

  10. #10
    Senior Member Sootshe's Avatar
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    Quote Originally Posted by spkrman57 View Post
    That will change the math somewhat.

    Ron sends...
    Sorry, the motorboard is 1" thick, not 1" in diameter.

    The throat diameter is 1.25 inches.

  11. #11
    Senior Member Sootshe's Avatar
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    Quote Originally Posted by stephane RAME View Post
    Thanks Stephane....haven't come across this before.
    Looks like the response is already going to be down at least 6db at 6K anyway.

  12. #12
    Senior Member Lee in Montreal's Avatar
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    I looked a bit closer at the Altec driver. It seems more like a 1Khz to 6Khz driver. With some CD correction it might go up to 10Khz where most horns will break-up.

    Here's the enlarged response graph in an Altec horn.


  13. #13
    Senior Member Sootshe's Avatar
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    Quote Originally Posted by Lee in Montreal View Post
    I looked a bit closer at the Altec driver. It seems more like a 1Khz to 6Khz driver. With some CD correction it might go up to 10Khz where most horns will break-up.Here's the enlarged response graph in an Altec horn.
    Thanks Lee,You can easily get hoodwinked with some of these components & their claimed responses. I would agree that the response would only be flat to 6K after viewing these graphs & from there starts to fall away. This at least gives me a starting point to determine where to bring the tweeter in.Makes you wonder what the real response of the GPA 390 driver is......they claim 300-7K, but again, no parameters of the response deviation within this range. Whatever the case, looks like the 399 will be suitable if I run 3 way & cross over around 6-7K, so I'm sure the horn will cope with this OK.Thanks,John
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  14. #14
    Unabashed Speakerholic cosmos's Avatar
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    Tractrix Horns

    If you build it, it's going to look pretty much or exactly like these.
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  15. #15
    Senior Member louped garouv's Avatar
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    what's up with the phase plug on that woofer?

    to help with "beaming" of higher freqs?


    looking good, nonetheless!

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