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Thread: LE15a frequency response?

  1. #1
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    LE15a frequency response?

    Anyone know the actual frequency response of the LE15a or have a graph? I will be running the 15a in a folded horn enclosure with an LE85 and an 075. When younger I use to listen to music way too loud and had issues with blowing the LE85. After several new diaphragms I put in a call to JBL (this was in the 80's) and was told the LE85 really didn't do well down to 500Hz. My solution back then was to add a 10" mid driver and crossover at 500 with the LE15a and 2500 for the LE85. That set of speakers is long gone but I'm putting together a new set with the folded horn enclosure and do not want to use a 10" mid. I will be building my own crossovers (24 dB rolloff, Linkwitz-Riley) and wanted to go a little higher than the 500 Hz of the LX5 to protect the LE85. I was originally thinking 800 Hz but the only literature I can find on the LE15a says 600 Hz is to highest recommendation for it. I think the LX5 is a 12 dB rolloff, maybe going to 600 Hz and rolling off at 24 dB is enough to protect the LE85 (and not listening too loud!). Also, I'm not that familiar with folded horn designs ... will they even go up to 600 Hz?

    Help! Any advice, pointer, recommendation would be appriciated.

    Thanks,

    Eric M.

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    Eric,

    300 to 400hz is about the top-end extent of what you can expect from a 15" woofer working within a folded horn.

    Also, the le15a was never known to be a good horn driver ( merely adequate > it's best suited to a bass reflex type alignment, IMHO )

    You might want to rethink your project.

    That said, the 600hz - 1K response of a le15a looks no worse than a 2235H ( to these eyes ).




  3. #3
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    Thanks. I had not thought about switching out the LE15a for something better suited for the folder horn design. I can certainly do that. It sounds like due to the cabinet design, I'm really limited to a max of 400 Hz and will need to figure out something for above that. With that in mind (and sticking to a 15" driver), it looks like the 2235H might be a better choice. Could you recommend any other woofer that might be better suited for this application?

    I was looking through the "library" here and found what looks like the folded horn design I have. I'll try to find it again and post a link.

    I came across these cabinets on Saturday and was going to pull the drivers and dump the cabinets until I took a closer look at them. They are unique and I thought it would be a nice addition. I'm selling a pair of 220 TI, these will take their place.

    Thanks,
    Eric M.



    Quote Originally Posted by Earl K View Post
    Eric,

    300 to 400hz is about the top-end extent of what you can expect from a 15" woofer working within a folded horn.

    Also, the le15a was never known to be a good horn driver ( merely adequate > it's best suited to a bass reflex type alignment, IMHO )

    You might want to rethink your project.

    That said, the 600hz - 1K response of a le15a looks no worse than a 2235H ( to these eyes ).




  4. #4
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    Enclosure #34

    http://www.lansingheritage.org/images/jbl/plans/c34/page2.jpg


    http://www.lansingheritage.org/image.../c34/page1.jpg

    My cabinet is a little different in that there is some sort of bracket under the woofer (at the horn exit) that hangs a 175 or LE85.

    JBL is actually calling for a 130a and 175 w/ option for 075 add on.
    Do you think the 130a would be a good option for this? JBL is claiming crossover at 1200 Hz (N1200) which is higher than I need to go with the LE85. But, is this folded horn still limited to about 400 Hz at the high end?


    Thanks,
    Eric

  5. #5
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    Quote Originally Posted by Eric M. View Post
    Enclosure #34

    http://www.lansingheritage.org/images/jbl/plans/c34/page2.jpg


    http://www.lansingheritage.org/image.../c34/page1.jpg

    My cabinet is a little different in that there is some sort of bracket under the woofer (at the horn exit) that hangs a 175 or LE85.

    JBL is actually calling for a 130a and 175 w/ option for 075 add on.
    Do you think the 130a would be a good option for this? JBL is claiming crossover at 1200 Hz (N1200) which is higher than I need to go with the LE85. But, is this folded horn still limited to about 400 Hz at the high end?


    Thanks,
    Eric

    The horn you're showing ( links to ) is a "Back-Loaded-Horn" ( aka; BLH ).

    The back wave combines with the front wave at around 300hz ( so above 300hz the output is all about what comes directly from the cone ).

    You can effectively use a 2225H or a 2226H in that type of hybrid horn box.

    The preferred woofer/horn driver crossover point will be determined by the however high the woofer reaches and the low-end limit of the horn/driver combo.

    IOW; My previously mentioned folded horn limit of @ 300hz no longer applies.


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    Earl, thank you for your help. I'll run the 2225H and crossover at 800. The 2225 is good to 1200 and I should not have any issues with my LE85 crossing that high.

    Thanks again,

    Eric


    Quote Originally Posted by Earl K View Post
    The horn you're showing ( links to ) is a "Back-Loaded-Horn" ( aka; BLH ).

    The back wave combines with the front wave at around 300hz ( so above 300hz the output is all about what comes directly from the cone ).

    You can effectively use a 2225H or a 2226H in that type of hybrid horn box.

    The preferred woofer/horn driver crossover point will be determined by the however high the woofer reaches and the low-end limit of the horn/driver combo.

    IOW; My previously mentioned folded horn limit of @ 300hz no longer applies.


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