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Thread: Which horn on JBL 4560?

  1. #16
    Senior Member RMC's Avatar
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    Hi Soulman,

    RE: "I believe the problem with these cabinets is the large distance between the horn and the woofer."

    I have something else which may be relevant to your sound problem.

    From the picture you posted, and subject to the perspective (depth) a viewer may have, it appears to me the MF/HF drivers are somewhat behind on top of the cab.

    According to J. Eargle (Handbook of Sound System Design, chapter: Dividing Networks/Components Matching, section: Physical Placement of HF and LF Elements), the horn should be mounted on top of cab with its mouth flush with the front of the enclosure.

    "A good rule to follow is this: mount the HF horn so that its mouth is flush with the upper edge of the LF enclosure. Then, make the polarity test and determine which poling, if either, results in the greatest output. (...) Details of this are shown in Figure 7-6B. The advantages of keeping the HF horn mouth flush with the front of the LF enclosure are minimized interferences in the crossover region and smoother vertical polar response in the crossover range." (p. 129)

    There are sketches explaining this, but I'm not at liberty to reproduce all that because of copyright issues.

    However, a small text says: "HF horn flush with LF enclosure, Displacement about wavelength at crossover; therefore, wire HF driver for maximum output: both outputs in phase at crossover" (p. 128)

    Hopefully the above may help with the issue. Regards,

    Richard

  2. #17
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    Quote Originally Posted by RMC View Post
    Hi Soulman,

    RE: "I believe the problem with these cabinets is the large distance between the horn and the woofer."

    I have something else which may be relevant to your sound problem.

    From the picture you posted, and subject to the perspective (depth) a viewer may have, it appears to me the MF/HF drivers are somewhat behind on top of the cab.

    According to J. Eargle (Handbook of Sound System Design, chapter: Dividing Networks/Components Matching, section: Physical Placement of HF and LF Elements), the horn should be mounted on top of cab with its mouth flush with the front of the enclosure.

    "A good rule to follow is this: mount the HF horn so that its mouth is flush with the upper edge of the LF enclosure. Then, make the polarity test and determine which poling, if either, results in the greatest output. (...) Details of this are shown in Figure 7-6B. The advantages of keeping the HF horn mouth flush with the front of the LF enclosure are minimized interferences in the crossover region and smoother vertical polar response in the crossover range." (p. 129)

    There are sketches explaining this, but I'm not at liberty to reproduce all that because of copyright issues.

    However, a small text says: "HF horn flush with LF enclosure, Displacement about wavelength at crossover; therefore, wire HF driver for maximum output: both outputs in phase at crossover" (p. 128)

    Hopefully the above may help with the issue. Regards,

    Richard
    You mean the lf cabinet and horn "look" at the same direction?

  3. #18
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    I suspect he means the vertical distance between the woofer and the horn. In front loaded speaker systems this distance would likely be less than one wavelength at 1khz. When listening at a distance of two or three meters this doesn't have a big effect on arrival times from two sources and thus doesn't cause significant comb filtering. Your speaker set up has a much larger vertical distance well over a wavelength at an 800 hz crossover. Less of an issue when listening at the 10-20 meters this speaker cabinet was designed for but pretty noticeable in a home environment.

    Your
    Quote Originally Posted by retro soulman View Post
    You mean the lf cabinet and horn "look" at the same direction?

  4. #19
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    Quote Originally Posted by Riley Casey View Post
    I suspect he means the vertical distance between the woofer and the horn. In front loaded speaker systems this distance would likely be less than one wavelength at 1khz. When listening at a distance of two or three meters this doesn't have a big effect on arrival times from two sources and thus doesn't cause significant comb filtering. Your speaker set up has a much larger vertical distance well over a wavelength at an 800 hz crossover. Less of an issue when listening at the 10-20 meters this speaker cabinet was designed for but pretty noticeable in a home environment.

    Your

    Ok... i need better cabs and definitely not horn loaded ! Maybe a pair of 4507 would be way better

  5. #20
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    One trick people experimented with back in the day ( before we gave up on 4560s altogether ) was to mount a horn in the 4560 horn with the HF driver acting as a sort of low budget phase plug for the 15" low driver. Can't say I ever heard one myself but I did hear a similar concentric bass horn box that sounded pretty good ( well maybe not bad would be more accurate ). It was not as big a driver as a 2440, the driver we normally used on top of 4560s but I don't remember what it was, perhaps a 2425 or an EV. The horn was not a large 500 hz capable horn but again I don't remember what was used. Might be fun to play with if you have a small enough horn. Certainly would make the phase at crossover more coherent having an over sized coax.

    Quote Originally Posted by retro soulman View Post
    Ok... i need better cabs and definitely not horn loaded ! Maybe a pair of 4507 would be way better

  6. #21
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    Quote Originally Posted by Riley Casey View Post
    One trick people experimented with back in the day ( before we gave up on 4560s altogether ) was to mount a horn in the 4560 horn with the HF driver acting as a sort of low budget phase plug for the 15" low driver. Can't say I ever heard one myself but I did hear a similar concentric bass horn box that sounded pretty good ( well maybe not bad would be more accurate ). It was not as big a driver as a 2440, the driver we normally used on top of 4560s but I don't remember what it was, perhaps a 2425 or an EV. The horn was not a large 500 hz capable horn but again I don't remember what was used. Might be fun to play with if you have a small enough horn. Certainly would make the phase at crossover more coherent having an over sized coax.
    No small horns here! Lol . For now i add the 2380 horns with the 2440 drivers. Smooth sound but plastic alsoName:  20210106_205012.jpg
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  7. #22
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    Nothing wrong with well designed plastic horns. It’s aluminum that makes a poor material for horns. The 2350 & 55s had to be coated with plaster to reduce the resonance but never really eliminated it.

    Quote Originally Posted by retro soulman View Post
    No small horns here! Lol . For now i add the 2380 horns with the 2440 drivers. Smooth sound but plastic alsoName:  20210106_205012.jpg
Views: 162
Size:  98.0 KB

  8. #23
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    Keep in mind the JBL 2390 lenses were designed to be used with a baffle behind the lenses, I didn't see anything like that in your pictures.

    Cut a piece of plywood that's about 12 inches larger in all dimensions of the 2390 lens with the horn mounted in the center. You want to assemble it so the back of lens is directly resting on the plywood baffle.

  9. #24
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    Quote Originally Posted by Mike Caldwell View Post
    Keep in mind the JBL 2390 lenses were designed to be used with a baffle behind the lenses, I didn't see anything like that in your pictures.Cut a piece of plywood that's about 12 inches larger in all dimensions of the 2390 lens with the horn mounted in the center. You want to assemble it so the back of lens is directly resting on the plywood baffle.
    Name:  20210103_133407.jpg
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  10. #25
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    Quote Originally Posted by retro soulman View Post
    Name:  20210103_133407.jpg
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    Your already there!

  11. #26
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    Quote Originally Posted by Mike Caldwell View Post
    Your already there!
    Yeap i had the baffles but still not the sound i like :/

  12. #27
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    horn in cabinet

    Not my cabinets. Actually if anyone has photo's of my 4560's it would be Ian in Australia.... but that is another story. They ended up in my wife's office with horns stuffed into the cabinets and a 4 inch riser under the cabinet that replaced the volume lost to the the horn.

    Similar to this photo, lifted from the web. They actually worked better than they had any right too. And were eventually replaced with L-300's In some ways the 4560's altered thusly are better than the L-300's They certainly project "Live" or the illusion of live better than the L-300's


  13. #28
    Senior Member jbl4ever's Avatar
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    The 2345 horn fits in the above cutout well. If you use the 2425/26 you will have to take off the rubber magnet protector. Still have 4 pairs
    Name:  100_0178.jpg
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