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Thread: JBL 2445_46 frq.response

  1. #46
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    Quote Originally Posted by ivica View Post
    I will try to make a photo with "half removed back-cap".
    No need. It sounds like you know how to put them together properly.

  2. #47
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    Quote Originally Posted by 4313B View Post
    No need. It sounds like you know how to put them together properly.
    Well Tom,

    It's still a mystery why your two new diaphragms don't perform correctly .

    I suggest that you take both back to your JBL dealer and ask him to install them into either a 2450/1 or 2446/7 driver ( from his own stock ) . Pay him to do it , if that is what it takes to get this done .

    Then take some response measurements ( at the JBL dealers shop ) of the diaphragms fitted into the proper drivers ( use your 2311 horn . This should prove ( or disprove ) that your diaphragms can be made to work correctly .

    It's possible ( maybe unlikely ) , those diaphragms just won't ever fit into your ( 2 ) 2445 drivers .

    - I have a new D8R2450SL diaphragm that just won't fit into any of the ( 8 ) 2440/1 drivers that I own . This diaphragm cost me @ $ 300.00 Cdn, eight or nine years back .
    - I wish I had followed similar advice to confirm ( or not ) if it was a manufacturing defect that prevents a proper fitup from happening with any of my drivers .
    - This diaphragm seems to be "tight" in the gap, implying to me that it's a bit wide in the voice-coil windings .
    - If I had been able to prove it couldn't be properly mounted into a JBL dealers' 2446, I might have been able to get a no-cost replacement ( based on the discretion of the dealer ) .
    - It was a somewhat expensive mistake on my part to not findout why this diaphragm won't work with my stuff .

    Anyways, there's one route to think about .


    <> cheers EarlK

  3. #48
    Senior Member ivica's Avatar
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    Quote Originally Posted by Earl K View Post
    Well Tom,

    It's still a mystery why your two new diaphragms don't perform correctly .

    I suggest that you take both back to your JBL dealer and ask him to install them into either a 2450/1 or 2446/7 driver ( from his own stock ) . Pay him to do it , if that is what it takes to get this done .

    Then take some response measurements ( at the JBL dealers shop ) of the diaphragms fitted into the proper drivers ( use your 2311 horn . This should prove ( or disprove ) that your diaphragms can be made to work correctly .

    It's possible ( maybe unlikely ) , those diaphragms just won't ever fit into your ( 2 ) 2445 drivers .

    - I have a new D8R2450SL diaphragm that just won't fit into any of the ( 8 ) 2440/1 drivers that I own . This diaphragm cost me @ $ 300.00 Cdn, eight or nine years back .
    - I wish I had followed similar advice to confirm ( or not ) if it was a manufacturing defect that prevents a proper fitup from happening with any of my drivers .
    - This diaphragm seems to be "tight" in the gap, implying to me that it's a bit wide in the voice-coil windings .
    - If I had been able to prove it couldn't be properly mounted into a JBL dealers' 2446, I might have been able to get a no-cost replacement ( based on the discretion of the dealer ) .
    - It was a somewhat expensive mistake on my part to not findout why this diaphragm won't work with my stuff .

    Anyways, there's one route to think about .


    <> cheers EarlK
    That is good proposal, but here in Serbia, such relationship with the barn company support is almost 'science-fiction". I was happy that I can get (I believe) original diaphragm, and such
    complicated investigation is out of any expectation ( sorry for my bad English).
    I wonder, may be, my drivers (I have bought them as second hand) have some systematic malfunctions, but lookig from out side I can not see.
    I have make some photos, so you can see in this thread.

  4. #49
    Senior Member ivica's Avatar
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    Quote Originally Posted by grumpy View Post
    voice coil depth (from underside of diaphragm 'diamond' surround to edge of former)
    measured at 4.5-4.6mm, best I could determine.

    pics. D16R2450


    Attachment 47128Attachment 47129Attachment 47130Attachment 47131Attachment 47132
    yes, on mine diaphragm almost the same, but the stickers are from inside of teh assembly. fixing the voice coil is done almost on teh same way
    Attached Images Attached Images      

  5. #50
    Senior Member ivica's Avatar
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    Quote Originally Posted by Earl K View Post
    Well Tom,

    It's still a mystery why your two new diaphragms don't perform correctly .

    I suggest that you take both back to your JBL dealer and ask him to install them into either a 2450/1 or 2446/7 driver ( from his own stock ) . Pay him to do it , if that is what it takes to get this done .

    Then take some response measurements ( at the JBL dealers shop ) of the diaphragms fitted into the proper drivers ( use your 2311 horn . This should prove ( or disprove ) that your diaphragms can be made to work correctly .

    It's possible ( maybe unlikely ) , those diaphragms just won't ever fit into your ( 2 ) 2445 drivers .

    - I have a new D8R2450SL diaphragm that just won't fit into any of the ( 8 ) 2440/1 drivers that I own . This diaphragm cost me @ $ 300.00 Cdn, eight or nine years back .
    - I wish I had followed similar advice to confirm ( or not ) if it was a manufacturing defect that prevents a proper fitup from happening with any of my drivers .
    - This diaphragm seems to be "tight" in the gap, implying to me that it's a bit wide in the voice-coil windings .
    - If I had been able to prove it couldn't be properly mounted into a JBL dealers' 2446, I might have been able to get a no-cost replacement ( based on the discretion of the dealer ) .
    - It was a somewhat expensive mistake on my part to not findout why this diaphragm won't work with my stuff .

    Anyways, there's one route to think about .


    <> cheers EarlK
    I put some photos
    Attached Images Attached Images   

  6. #51
    Senior Member ivica's Avatar
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    [QUOTE=grumpy;293749]voice coil depth (from underside of diaphragm 'diamond' surround to edge of former)
    measured at 4.5-4.6mm, best I could determine.

    pics. D16R2450


    Thanks for teh nice photos. As I told you the voice coil is relatively unxpectable "short".
    On my mind one idea "come", may be my magnet is weak , I have no ide how to measure the
    magnetic field in the gap (off course I have no specila measuring equipmemnt )

  7. #52
    Senior Member ivica's Avatar
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    [QUOTE=grumpy;293749]voice coil depth (from underside of diaphragm 'diamond' surround to edge of former)
    measured at 4.5-4.6mm, best I could determine.

    pics. D16R2450

    One 'interesting' thing while cleaning the voice coil gap, I realized that this narrow gap is VERY DEEP about 30mm> While pitting this in AkAbak simulator this small box can make the very deep notch around the frequency we are toking about.
    Here is AkAbak Script and its response.
    what is iportant deep notch around 3kHz and smaller here on 9kHz (on measured on 10kHz),
    Black line on attached figure,
    but if depth of the voice coil gp is reduced from 30mm to 8mm then the figure would be different-red line
    Attached Images Attached Images  
    Attached Files Attached Files

  8. #53
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    Quote Originally Posted by grumpy View Post
    voice coil depth (from underside of diaphragm 'diamond' surround to edge of former)
    measured at 4.5-4.6mm, best I could determine.

    Quote Originally Posted by ivica View Post
    One 'interesting' thing while cleaning the voice coil gap, I realized that this narrow gap is VERY DEEP about 30mm> .

    - While pitting this in AkAbak simulator this small box can make the very deep notch around the frequency we are toking about.
    - Here is AkAbak Script and its response.
    - What is important ( is the at ) deep notch around 3kHz and (the ) smaller here on 9kHz (on measured on 10kHz),
    Black line on attached figure,
    - But if depth of the voice coil gp is reduced from 30mm to 8mm then the figure would be different-red line


    - Maybe it's nothing but , JBL doesn't use the type of binding(connection) posts shown in the above picture . That type was commonly used by P-Audio copies of the 2445 driver .
    - Plus, the black connector is supposed to be on the left-hand side .
    - They could have been switched by someone ( so as to follow normal color-coding /polarity conventions, I suppose ) .

    The 1.18" depth of the gap/top-plate ( which you just mentioned ) seems wrong for a bonafide JBL .
    - Are you sure of that measurement ?

    - Anyways, you need to have someone with a 2445 driver measure the depth of the gap ( I don't own any 2445 driver ) so that you can compare to what you have .

    <> cheers

  9. #54
    Senior Member ivica's Avatar
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    [QUOTE=Earl K;293898]
    Quote Originally Posted by ivica View Post



    JBL doesn't use the type of binding(connection) posts shown in the above picture . That type was commonly used by P-Audio copies of the 2445 driver .

    The 1.18" depth of the gap/top-plate ( which you just mentioned ) seems wrong for a bonafide JBL .
    - Are you sure of that measurement ?

    - Anyways, you need to have someone with a 2445 driver measure the depth of the gap ( I don't own any 2445 driver ) so that you can compare to what you have .

    <> cheers
    May be your right that this is bad copy of 2445 driver. In order to measure the 'depth' of voice coil gap I haev used a strip of hard paper and pushed it in until reached the bottom. May be there is an error of 1mm but for sure about 30mm. I will try to measure the width (under magnet pole plate). May be it is wider than the gap at the top. The problem is that if I would "discover" a large cavity under pole plate. How to "fill-in" such cavity, and what effect such experiment would produce. Concerning the AkAbak simulation, such cavity can introduce such notch about 3kHz. Generally the problem for such experiments is that you can not disassemble the driver with "home equipment"

  10. #55
    Senior Member grumpy's Avatar
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    I'm 99.999999999% sure that's not a 2445 or a JBL driver at all.

    That side view and the phase plug pictures are not what I would expect.

    You might want to read through this thread:

    http://www.audioheritage.org/vbullet...read.php?28776

  11. #56
    Senior Member ivica's Avatar
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    Quote Originally Posted by grumpy View Post
    I'm 99.999999999% sure that's not a 2445 or a JBL driver at all.

    That side view and the phase plug pictures are not what I would expect.

    You might want to read through this thread:

    http://www.audioheritage.org/vbullet...read.php?28776
    Yes, I have red that before. I am afraid that mines are some copy (unfortunately bad)

  12. #57
    Senior Member grumpy's Avatar
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    It is still interesting (at least to me), that your AkAbak model assumptions seem to correspond to the "problem" driver behavior.

    At least one mystery was solved.

  13. #58
    Senior Member ivica's Avatar
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    Quote Originally Posted by grumpy View Post
    It is still interesting (at least to me), that your AkAbak model assumptions seem to correspond to the "problem" driver behavior.

    At least one mystery was solved.
    Well, to be honest, in AkAbak software there are several examples where I have find the example for model of compression driver and that was starting point.
    If you would like to "experiment" on computer I suggest:

    http://www.randteam.de/_Software/AkA...ad-AkAbak.html

    where you can download AkAbak....

  14. #59
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    ...someone went to extraordinary measures to copy this driver and, from the visual inspections, it was diffucult for the experts here to identify them as fakes.

    OK, so what have we learned from this?

    1. Harman to Houston: "We have a problem!"

    2. The technology that is necessary to manufacture modern JBL drivers ("knock-offs") is not as complex as one might initially think.

    3. Thre is a significant cost advantage to manufacture these in Asia (??) Vs the USA - otherwise Asian cheats (??) would not do this. (Remember - Toyota and Honda "copied" GM and Ford in the 1960s)

    4. Someone is likely to use the experience they gained in making the knock-offs to develop new OEM products that are competitive in the marketplace with JBL and, eventually that surpass the performance of JBL.

    5. The participants in today's world economy do not always play fair.

    6. If I'm the CEO of Harman, I need to keep close tabs on what is happening in the marketplace and to take appropriate action to avoid being uterly CRUSHED!

  15. #60
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    ...one other thing...

    I'm going home tonight and I plan to check my pair of 2445Js to see if they are real. When I installed a new pair of OEM 8 ohm frames about one year ago, I remember not being able to see down the throat to the phase plug, so I should be OK.

    ...This blows!

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