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Thread: Which horns for JBL 2451 Be drivers?

  1. #31
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    This thread is gold! Couple quick questions: Is there a difference between the 2450-SL phragm and the 2451-SL?
    Assumption: I can use an 8 ohm phragm in a 16 ohm body and it will operate as an 8 ohm driver (nominal).

  2. #32
    Senior Member pos's Avatar
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    Quote Originally Posted by wrager View Post
    This thread is gold! Couple quick questions: Is there a difference between the 2450-SL phragm and the 2451-SL?
    Diaphragms are supposed to be the same, but you will sometimes see aquaplas on the surrounds and sometimes not....
    There also was a latter 2450SL-A driver with a ribbed diaphragm.

    Assumption: I can use an 8 ohm phragm in a 16 ohm body and it will operate as an 8 ohm driver (nominal).
    Yes
    (though I would personally always choose a 16 ohms diaphragm over an 8 ohms one when given the choice)

    Note that the 476Be and 476Mg are 16 ohms nominal despite what their EDS says.

  3. #33
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    Quote Originally Posted by pos View Post
    Yes
    (though I would personally always choose a 16 ohms diaphragm over an 8 ohms one when given the choice)
    Thank you POS, you are always a great help! Why would 16 ohm be a better choice? What am I giving up, 3dB?

  4. #34
    Senior Member pos's Avatar
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    You're welcome

    This was touched on in the third post of that thread:
    Quote Originally Posted by pos View Post
    Noise (hiss) is the biggest issue with high sensitivity devices in an active system.
    16 ohms will give you a 3dB advantage there, and also reduce amplifier distortion, but at the cost of 3dB reduction in max SPL capabilities (if the amp is the limiting factor).
    That said some low power amplifiers with very low residual noise might be more at ease with a 8 ohms load, like the LPUHP amps, but this is a rare case.

    IMHO 16 ohms nominal is generally the better choice there.
    JBL even went to 32 ohms nominal with the D2 (dual 16 ohms coils in series), and only wire them as 8 ohms (coils in parallel) in passive PA speakers.
    16 or 32 ohms compression drivers will even let you use some top headphones amplifiers that no speaker amplifier can touch in term of residual noise and distortion: https://www.massdrop.com/buy/massdro...near-amplifier

    Another peculiar benefit of using a 16 ohms compression driver compared to an 8 one is that you will be able to use a smaller and cheaper protection cap

  5. #35
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    Quote Originally Posted by pos View Post

    Memebr Woody designed a 1.5" version (3/4 scaled down) of the Arai 290 horns, and they seem to measure and sound pretty good!
    Can you share any measurements regarding this 1,5"-yuichi horn?

    I was told simply scaling down a horn doesn´t really work, it rather has to be redesigned and the proportions adjusted...
    So I´m really interested if this horn performs as good as the full-size yuichi a290

  6. #36
    Senior Member ivica's Avatar
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    Quote Originally Posted by Dr.db View Post
    Can you share any measurements regarding this 1,5"-yuichi horn?

    I was told simply scaling down a horn doesn´t really work, it rather has to be redesigned and the proportions adjusted...
    So I´m really interested if this horn performs as good as the full-size yuichi a290
    Hi Dr.db,

    I do not think that 3/4 scaling down would be the best solution. As You know that all JBL 2-inc CD drivers has (almost conical or exponential) horn that 'convert' 1.5inch phase plug opening to 2inch driver mouth. Such horn length is about 6cm to 7cm, so such "transition small horn" can be made if You want A290 to connect with JBL 1.5inch driver.
    Other solution can be done using Dr.Yuichi recalculation procedure but starting with 1.5inch driver mouth instead of 2inch. I do not think that it would differ much then previously mentioned adding small 'transition' horn.

    I think that EQ 2451Be (if it is Trex-Be) would be greater problem, but if You are using JBL Be (476) diaphragm, then I believe that there would be no problem about EQ it.


    regards
    ivica

  7. #37
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    2451Be EQ

    Quote Originally Posted by ivica View Post

    I think that EQ 2451Be (if it is Trex-Be) would be greater problem, but if You are using JBL Be (476) diaphragm, then I believe that there would be no problem about EQ it.

    regards
    ivica
    Ivica,

    what is the problem with putting EQ on 2451Be (Trex-Be), as opposed to JBL Be (476)?

    Herman

  8. #38
    Senior Member ivica's Avatar
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    Quote Originally Posted by Herman Chigrin View Post
    Ivica,

    what is the problem with putting EQ on 2451Be (Trex-Be), as opposed to JBL Be (476)?

    Herman
    HI Herman,

    I would expect that 4" Trex-Be would have large dropout over 10kHz compared to JBL 476-Be diaphragm, as 2440 vs 2441 diaphragms have.

    regards
    ivica

  9. #39
    Senior Member richluvsound's Avatar
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    2450 sl be

    An interesting thread indeed !

    I'm looking for a horn that behaves as close as possible to the TH4003 in its dispersion pattern . Talking to Ari about the M2 horn , 4367 but , I'd like to use 650htz as a the crossover point . That leaves the Autotech range or ...get the throat adapter and making a A290 . I have H9800 clones , but not convinced they'll come anywhere near in a 2-way set up .
    I want to avoid DSP .... I'd rather take my time and go passive . This my first speaker design from scratch .... I have some very good people helping me and I'm not in a rush .... So here goes . I'll start a thread here and over on diyaudio.com

    Parts: 2450SL /4016 BE
    JBL 1500AL - 150 litre
    Horn ?


    Rich

  10. #40
    Senior Member Ian Mackenzie's Avatar
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    Have a look at the Jbl 2384

    It’s getting good feedback from diy

  11. #41
    Senior Member richluvsound's Avatar
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    Quote Originally Posted by Ian Mackenzie View Post
    Have a look at the Jbl 2384

    It’s getting good feedback from diy
    Its huge Ian , and not the prettiest thing to look at . Have you tried any of the Tractix horns ? I can get the 4367 horn ,but I was really hoping to keep the baffle as narrow as possible .
    The price of the 2384 is good , Scan it and CNC in wood .

    http://www.diyaudio.com/forums/multi...z-510-a-5.html


    Rich

  12. #42
    Senior Member 1audiohack's Avatar
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    How about a pair of clone 4338’s with billet “aluminium” throats?

    They are 20.25” X 8.625”
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    If we knew what the hell we were doing, we wouldn't call it research would we.

  13. #43
    Senior Member 1audiohack's Avatar
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    They are permanent mold cast from mineral loaded rigid urethane.

    Barry.
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    If we knew what the hell we were doing, we wouldn't call it research would we.

  14. #44
    Senior Member Ian Mackenzie's Avatar
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    Quote Originally Posted by richluvsound View Post
    Its huge Ian , and not the prettiest thing to look at . Have you tried any of the Tractix horns ? I can get the 4367 horn ,but I was really hoping to keep the baffle as narrow as possible .
    The price of the 2384 is good , Scan it and CNC in wood .

    http://www.diyaudio.com/forums/multi...z-510-a-5.html


    Rich
    Hi Rich,

    Not recently. Depending on your aesthetic needs the Le Cléac’h AH-340 (600mm) could be interesting?

    If you are doing a passive crossover from scratch you really need a diy friendly horn

    http://www.azurahorn.com


    The 2384 is the only modern Jbl horn readily available that will do 650 hertz properly.

    If you relax that criteria to 750-800 hertz you can accommodate a narrower baffle.

  15. #45
    Senior Member Ian Mackenzie's Avatar
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    Hi Barry,

    They are nice. I have heard the 4338 and it’s really nice.

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