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Thread: 2441 distortion

  1. #1
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    2441 distortion

    Iīve been told the 2441 drivers are not very low in distortion.
    What are the reasons for these distortions?

    What has been done in the more modern drivers to reduce distortion?
    Is there a significant difference between 2" and 1,5" throat-size?
    Or is the diaphragm material a major factor?

  2. #2
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    I think you will find relevant answers to your questions in the two documents below. Regards,

    Richard

    JBL Tech Note - Vol.1, No.8 COMPRESSION DRIVERS.pdfJBL TECH NOTE V1 N 21 OPTIMIZED APERTURE.pdf

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    Thanks a lot, great links!!

    So the main factor in reducing distortion is the 1,5" throat vs. the old 2" throat. As the 1,5" throat drivers have a more rapid flare rate, they will produce less thermal pressure e.g. distortion.
    By comparing the distortion graphs of 2" vs. 1,5" drivers, itīs obvious that 1,5" driver have about half the dispersion above 5khz than 2" drivers. But between 1-5khz they are very similar in distortion.
    Now I would assume that the human ear is much more sensitive below 5khz than above. So is this reduced distortion above 5khz that important?
    Or does the distortion above 5khz affect the distortion below 5khz as well? Something like intermodulation maybe, I have heard that once before but don`t understand it.

    Is there a difference in distortion between aluminum and berryllium diaphragms as well?
    For example the TAD 4001...
    It has a different diaphragm than JBL 2441, but it has the same old 2" throat angle. So in theory it should suffer from the same distortion, right?

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    Hi Dr. db,

    RE "Now I would assume that the human ear is much more sensitive below 5khz than above."

    Unfortunately, that statement is subject to nuances. The human ear's maximum sensitivity is at about 4 khz. At some points the statement is correct. However, as you go into lower frequencies like mid-bass the ear's sensitivity is lower and decreases further with lower frequencies.

    Note the above is also level dependent, since low frequencies get more in line with higher sound levels (say 90-110 db). The ear is less sensitive to higher frequencies from about 5 khz and up regardless of level.

    Initially established by Fletcher & Munson and later revised by Robinson & Dadson, the equal loudness contours were again revised 2003 or so for the purpose of ISO standardization, where better agreement was found with Fletcher & al specially in bass range, instead of Robinson & al. The curves are based on experiments with numerous humans and decades later they still appear in many Audio Engineering books, like in Eargle's.

    When the graph with the curves is flipped over it shows roughly the ear's "frequency response" based on levels. Google preferably "Fletcher & Munson equal loudness contours" to see what the curves are all about.

    In the old days I had a Yamaha integrated amp with a continuously variable loudness control which followed more or less the equal loudness contours. Turning the knob counter clockwise basically reduced the mids level where ear sensitivity is high to give the impression that LF and HF were at comparably perceived levels. Regards,

    Richard

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    Hi Richard,

    thanks a lot for your explanation.

    Do you know if the TAD 4001 is significantly lower in distortion than a JBL 2441?
    They both share the same throat e.g. flare rate, so the TAD should produce the same distortions...
    Or is the diaphragm material a major factor as well?

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    Hi Dr. db,

    I don't have the data to support an answer to both of your questions. Guessing distortion levels based on diaphgram metal fatigue info I have would be quite hazardous... Sorry. Regards,

    Richard

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    No problem, thanks so far

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