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Thread: The purpose of JBL E145

  1. #16
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    Re: Jacked Up Numbers

    Originally posted by Earl K
    Hi RobG
    You and I went through this a couple of forums ago. What TS numbers were/are wrong. I remember you reporting that JBL said to measure it yourself,,, etc. The numbers I use seem to give the appropriate curves for this class of speaker. Here's a pdf of a 2 cu' , 50 Hz tuning I did quite a while ago ( ignore the date stamp ) . How does this curve compare to what you see with your tuning-prediction software?

    regards <. Earl K
    Well for one thing...

    Given a value for Fs of 35 Hz, Mms of 0.055 kilograms, and Sd of 0.090 square meters, Vas SHOULD be ~427.7 liters instead of 274.7.

    This is given by:
    Vas = (2 * pi * Fs)^2*Mms)^-1 * p0 * c^2 * Sd^2 * 10^3
    Where Vas is in liters
    Mms is in kilograms
    p0 is 1.18 kilogram/cubic meter (mean density of air)
    c is 345 meters/second (speed of sound)
    Sd is in square meters

    Dyslexia perhaps?
    I think using 427.7 instead of 274.7 jacks up the reference efficiency though... I'd have to work through it...

  2. #17
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    Anyway, back to:

    "I was talking with a man here in sweden who liked
    the e-145 more than the 2235 up to ca 600hz, more
    attack he said.."


    Looking at the TS parameters both drivers have the same Qts, the 2235H has a bit better mechanical control with it's lower Qms and the E145 has a bit better electrical control with it's lower Qes.

    The 2235H clearly has a "better" Bl factor but...

    155 grams / (20.5 Newton/Amperes * (1/6.0) Amperes) = 45.4 grams/Newton

    55 grams / (16.1 Newton/Amperes * (1/5.7) Amperes) = 19.5 grams/Newton

    Wow! If my math is correct, I guess we can see why the E145 has such a nice attack
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  3. #18
    Moderator / Treasurer/Marketplace Czar boputnam's Avatar
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    Dyslexia and typos...

    I've noticed some myself - in the 1982 Pro brochure, p5 JBL appears to have swapped the Enclosure Volume figures for the 4345 and 4355...
    bo

    "Indeed, not!!"

  4. #19
    Senior Member Niklas Nord's Avatar
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    Great, this thread has become wery interesting.
    Is the e-145 a rare object in the USA?

    Are there one alnico version and one ferrite version ?
    Best Regards
    .Niklas Nord, Stockholm Sweden
    Proud owner of the Project K2 s9500 system

  5. #20
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    No the E145 isn't rare.

    Note that it's the same transducer as the 150-4H (Everest).

    http://www.audioheritage.org/html/pr...bl/everest.htm

    The K-series are alnico, the E-series are ferrite. JBL increased the flux densities in the E-series though...

    Note that these TS parameters haven't been checked yet so some might be "wrong"

    ***********
    K120, K151, E120, E145 look suspect
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    Last edited by 4313B; 06-22-2003 at 05:33 AM.

  6. #21
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    Question E145 Effective Piston Diameter

    Hello,

    If someone has an E145, I need to know the effective piston diameter, preferably in millimeters. I already have "published" notes, I need the "real deal".

    Thanks

  7. #22
    Administrator Robh3606's Avatar
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    Well I can measure my 801C cone. It's different cone kit than the 145. Don't know if it because of the central spider or if the cones/surround are different.

    Rob

  8. #23
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    Re: E145 Effective Piston Diameter

    Originally posted by Giskard
    Hello,

    If someone has an E145, I need to know the effective piston diameter, preferably in millimeters. I already have "published" notes, I need the "real deal".

    Thanks
    Giskard

    I have three E145's. One NOS, two that are reconed with what appears to be a generic kit ("10455" stamped on cone.... looks exactly like the JBL kit, but slightly heavier).

    Let me know how to measure the "piston diameter" and I will get you a number. Sorry, I'm pretty much a novice when it comes to the technical stuff


    This message comes from JBL Dog

  9. #24
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    Re: E145 Effective Piston Diameter

    Hi JBL Dog,

    Measure from the middle of the surround Thanks!
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    Last edited by 4313B; 06-22-2003 at 03:31 PM.

  10. #25
    "new and improved" JBL Dog's Avatar
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    Giskard:

    I measured it to be exactly 13.25 inches. A conversion to millimeters is 336.55. Hope this helps.

    This message comes from JBL Dog

  11. #26
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    Great! Thanks a bunch

    So that means the Vas of the E145 is 427.7 liters instead of the published 274.7 liters. It makes sense since JBL likes to put this driver in a 4.0 cubic foot volume tuned to 40 Hz.
    Last edited by 4313B; 06-22-2003 at 07:06 PM.

  12. #27
    Senior Member sa660's Avatar
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    E145 and 801C

    Originally posted by Robh3606
    I would love to get my hands on a pair of them to drop in my mains. My 801C is based on it and it is one really nice sounding driver.
    Rob
    ROB,
    I have 2 E145 that need recone and I am wondering about getting them done.
    Can you describe the frame of the 801C?
    The E145 has a thicker frame about 3/4 " thick to allow for a deeper cone that usual JBL chassis. Is the 801C the same?

    Do you have characteristic of the vents and volume of the box for the 801C.

    Regards,
    Regards,
    Richard,
    JBL 2450+JBL E145

  13. #28
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  14. #29
    Administrator Robh3606's Avatar
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    The 801C uses the same frame as the E-145. The diference between the volumes would be the volume taken by the 2425S hanging off the back. Take a look at the attached photo. There is a recess in the UREI cabinet the frame is thicker than it looks in the photo. If you talk to JBL they told me to use the T/S for the E-145. I have always wondered about that though looking at the -3db for the 811C monitor. I think they have the box tunned tight for maximum transient response.

    Rob
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    Last edited by Robh3606; 06-23-2003 at 07:33 PM.

  15. #30
    Administrator Robh3606's Avatar
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    Some decent pictures
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