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Thread: LE-10 used up to 1000Hz.

  1. #1
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    LE-10 used up to 1000Hz.

    Dear Sirs,

    I am setting up two 2-ways medium size monitors (i.e. woofer and horn).
    The horns, that I already own, have a good response from 1000Hz up.
    So I need a woofer able to go up to 1000Hz (the crossover is active with 24dB/octave slopes).
    A friend of mine have a pair of 10" LE-10 to sell.
    Are they good up to 1000 Hz ? or it would be better to look at a 8" ?
    Any other kind suggestion about JBL woofers (vintage or new) able to go up to 1000Hz ?
    As I said they will be cut at 1000Hz with a 24db/octave filter.

    Thank you very much indeed.
    Kind regards,

    beppe

    P.S. where can I find the LE-10's graph response (possibly with the indication of the point where it starts to become beaming)?

  2. #2
    Senior Member alexkerhead's Avatar
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    zilch will probably have graphs and a better answer, but yes, those should be fine up to 2000Hz.

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    Quote Originally Posted by alexkerhead
    zilch will probably have graphs and a better answer,
    but yes, those should be fine up to 2000Hz.
    Thank you very much indeed for your kind and valuable reply.
    Maybe I was worrying to much about this beaming effect.
    By the way can you give me your opinion about the LE-10 ?
    Any other even better 10" candidate for the 40-1000 Hz range (I have already renounced to very low frequencies as my listening room is just 5x7 meters).
    Thank you so much again.
    Kind regards,

    beppe
    Italy

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    - The whole le10 family ( alnicos & ferrites ) sound nice up to 1500hz , in my experience .
    - Le111H woofers are the same as Le10H / they just have a black front frame instead of the brushed aluminum.
    - You realize ( I hope ) that the le10 is an @ 89 db / 1 watt transducer .
    - You'll be padding down your compression driver a good 16 db .


    - Your "beaming" question needs to be put into some context.
    - At the crossover point to the horn (or any other domed transducer ) / it's nice to match the horns directional characteristics to that of the woofers (in the transitional/crossover area ).
    - This makes for a smoother transition from one transducer to the other.
    - Therefore, you may want to consider raising your crossover point ( depending on the horndriver combo you have ) .



    - You've been a member of this website since April.
    - Therefore, by now I think you should know that these woofers are highly considered by virtually everyone who owns them.
    -They have a nice deep coil winding ( for good Xmax ) / a 3" diameter coil winding / lots of coil length in the winding ( giving a decent BL figure which can be directly related to resolution ) / a nice application of Aquaplas ( to reduce harmonic disrtortions ) and on and on .
    - The pertinent statistics ( including Frequency Response ) are outlined in the "Transducer" Forum .

    Quote Originally Posted by beppe61
    Any other even better 10" candidate for the 40-1000 Hz range (I have already renounced to very low frequencies as my listening room is just 5x7 meters).
    - No, IMHO, there's no better JBL 10" woofer ( that offers linear response in the 40 to 1000hz range ).


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    Quote Originally Posted by Earl K
    -
    The whole le10 family ( alnicos & ferrites ) sound nice up to 1500hz , in my experience .
    - Le111H woofers are the same as Le10H / they just have a black front frame instead of the brushed aluminum.
    - You realize ( I hope ) that the le10 is an @ 89 db / 1 watt transducer .
    - You'll be padding down your compression driver a good 16 db.
    Thank you sincerely for your extremely kind and helpful advice.
    Actually I would like to use the compression driver (a 2") in unconventional way, mounted backwards and without the horn, like a normal dome mid-tweeter from 1000Hz up.
    In this way the actual sensitivity of the driver should be reduced (I do not know how much anyway. I have to try this).
    - Your "beaming" question needs to be put into some context.
    - At the crossover point to the horn (or any other domed transducer ) / it's nice to match the horns directional characteristics to that of the woofers (in the transitional/crossover area ).
    - This makes for a smoother transition from one transducer to the other.
    - Therefore, you may want to consider raising your crossover point ( depending on the horndriver combo you have ) .
    This is a very important point I was wrongly overlooking.
    Unfortunately I do not have any graph response of the horn's driver.
    At the crossover point then the dispersion of woofer and tweeter should match.
    I guess this could be difficult to achieve.
    Maybe I am misunderstanding, but shouldn't I have to lower the crossover point?
    The directionality of the woofer should increase going up with the frequency so the mismatch should be greater at 1500 than it is at 1000 Hz. Am I wrong ?
    - You've been a member of this website since April.
    - Therefore, by now I think you should know that these woofers are highly considered by virtually everyone who owns them.
    -They have a nice deep coil winding ( for good Xmax ) / a 3" diameter coil winding / lots of coil length in the winding ( giving a decent BL figure which can be directly related to resolution ) / a nice application of Aquaplas ( to reduce harmonic disrtortions ) and on and on.
    - The pertinent statistics ( including Frequency Response ) are outlined in the "Transducer" Forum .
    - No, IMHO, there's no better JBL 10" woofer ( that offers linear response in the 40 to 1000hz range ).
    This is more than enough for me.
    Thank you sincerely again.
    I will look thoroughly at the "Transducer" Forum .

    Kind regards,
    beppe

  6. #6
    Senior Member GordonW's Avatar
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    If you do the basic math, you can get a handle on the frequency that ANY 10" driver will start to beam. It's a dimensional thing, dependent on the diameter, more than any other factor.

    For a JBL LE10, that frequency will be around 1600 Hz. So, using it up to 1KHz, 24 dB/oct. lowpass, will be absolutely fine. Should be no need to worry about dispersion problems, whatsoever.

    Regards,
    Gordon.
    This Is Gordon's Page: www.geocities.com/gordonwaters

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    Quote Originally Posted by GordonW
    If you do the basic math, you can get a handle on the frequency that ANY 10" driver will start to beam.
    It's a dimensional thing, dependent on the diameter, more than any other factor.
    For a JBL LE10, that frequency will be around 1600 Hz.
    So, using it up to 1KHz, 24 dB/oct. lowpass, will be absolutely fine.
    Should be no need to worry about dispersion problems, whatsoever.
    Regards,
    Gordon.
    Dear Mr Gordon,
    thank you very much for your kind and valuable reply.
    I sincerely do not know of the existence of a relation between a woofer diameter and the frequency at which it starts to beam.
    I am very interested in this relation. Where can I find it ?
    Anyway 1600 Hz is much more than enough for my needs.
    Thank you very much again.
    Kind regards,

    beppe

  8. #8
    Senior Member GordonW's Avatar
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    The math is more complicated... but a simple way to calculate max usable frequency before "lobing" (where the speaker starts to audibly "comb filter itself", ie, having "dead zones" that come and go with position at different angles), is to NOT use the driver above a frequency where the cone diameter is ONE WAVELENGTH of sound at that frequency.

    A good reference, is to remember a wavelength at 1KHz, is 1.1 feet, or 13.2 inches, roughly. The effective radiating area (cone diameter plus half the surround diameter) of a JBL LE10 is around 8.25 inches... so, if you calculate the frequency of a 8.25" wavelength:

    ( (Wavelength at 1kHz)*(1khz) )/(wavelength under test) = (frequency under test).

    (13.2in.*1000)/8.25in. = 1600 Hz.

    A more rigid determination (the first "beam narrowing" frequency of beaming) would be to make the cone ONE HALF wavelength at the max frequency... that would be ONE HALF the frequency of the "lobing onset" frequency above. For an LE10, that would be 800 Hz. However, if your crossover is already starting to rolloff a bit at 800 Hz (which a 1KHz fourth-order crossover WOULD be- it'd already be down a close to 1dB there, and starting to go down fast), then you're fine... the horn would already be starting to "fill in" the response at 800 Hz a bit. So, lobing wouldn't be an issue, even under the strictest interpretations...

    Regards,
    Gordon.
    This Is Gordon's Page: www.geocities.com/gordonwaters

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    Quote Originally Posted by GordonW View Post
    The math is more complicated... but a simple way to calculate max usable frequency before "lobing" (where the speaker starts to audibly "comb filter itself", ie, having "dead zones" that come and go with position at different angles), is to NOT use the driver above a frequency where the cone diameter is ONE WAVELENGTH of sound at that frequency.
    A good reference, is to remember a wavelength at 1KHz, is 1.1 feet, or 13.2 inches, roughly.
    The effective radiating area (cone diameter plus half the surround diameter) of a JBL LE10 is around 8.25 inches... so, if you calculate the frequency of a 8.25" wavelength:
    ( (Wavelength at 1kHz)*(1khz) )/(wavelength under test) = (frequency under test).
    (13.2in.*1000)/8.25in. = 1600 Hz.
    A more rigid determination (the first "beam narrowing" frequency of beaming) would be to make the cone ONE HALF wavelength at the max frequency... that would be ONE HALF the frequency of the "lobing onset" frequency above. For an LE10, that would be 800 Hz. However, if your crossover is already starting to rolloff a bit at 800 Hz (which a 1KHz fourth-order crossover WOULD be- it'd already be down a close to 1dB there, and starting to go down fast), then you're fine... the horn would already be starting to "fill in" the response at 800 Hz a bit.
    So, lobing wouldn't be an issue, even under the strictest interpretations...
    Regards,
    Gordon.
    Dear Mr Gordon,

    thank you very much again for your extremely kind and thorough explanation.
    As you very well say the math is quite complicated.
    All in all and on this basis I think that a "sane" design cannot do without the actual graph responses of the drivers at different angles.
    And I understand that is very important that the dispersion properties of the different drivers match at the crossover points (very fundamental point I think).

    Thank you so much again.
    Kind regards

    beppe

  10. #10
    Member jack_bouska's Avatar
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    loudspeaker directivity

    [quote=GordonW;132341... but a simple way to calculate max usable frequency before "lobing" .....Gordon.[/quote]
    see:
    http://www.lansingheritage.org/image...tor/page02.jpg

    for a graphical plot of directivity vs piston diameter (in wavelengths)
    Jack

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    Quote Originally Posted by jack_bouska View Post
    see:
    http://www.lansingheritage.org/image...tor/page02.jpg
    for a graphical plot of directivity vs piston diameter (in wavelengths)
    Jack
    Thank you very much Mr Jack.
    A very interesting and valuable page.
    Kind regards,

    beppe

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