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Thread: 2405 upper limit

  1. #1
    Senior Member Mike F's Avatar
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    2405 upper limit

    Has anyone ever plotted the tweeters upper frequency response limit? My RTA measurements reveal a useable response to at least 20k but that is the instruments highest measureable band and judging by how effortlessly it makes it there, it seems reasonable that it can go yet further up. According to JBL publications, a -10 db point is claimed between 6k5 and 21k5 but at which end, low,high or both? My guess is the lower end.

  2. #2
    Senior Member grumpy's Avatar
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    They drop pretty fast after ~19KHz. Calling it -10dB at 21.5KHz
    is a reasonable description of their behavior. In use, I would think
    dropping it by 10dB below 6.5KHz (and more as frequency decreases)
    when planning crossover design would also be a useful user guide.
    The intended diffraction (giving it the wide horizontal dispersion)
    appears to be less functional below that freq.

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    FR Plot of my drivers:
    Attached Images Attached Images  

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    Senior Member pos's Avatar
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    Do you have a calibrated microphone?

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    Senior Member Mike F's Avatar
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    Quote Originally Posted by pos View Post
    Do you have a calibrated microphone?
    Bonjour POS,
    Oui, les microphones sont integre dans l`appareil.

    http://www.phonic.com/en/paa6.html

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    Senior Member Mike F's Avatar
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    Quote Originally Posted by neskor View Post
    FR Plot of my drivers:
    That is what I was looking for, thank you. What were the instruments used and measuring conditions?

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    Quote Originally Posted by Mike F View Post
    That is what I was looking for, thank you. What were the instruments used and measuring conditions?
    Software is HolmImpulse, mic is Behringer ECM8000 and sound card is M-Audio Fast track pro.
    Behringer is used with generic calibration file found on net, so use this plot as a guide
    One day I need to make that calibration file.

  8. #8
    Senior Member pos's Avatar
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    Quote Originally Posted by neskor View Post
    Behringer is used with generic calibration file found on net, so use this plot as a guide
    There is no such thing as a generic calibration file for the ECM8000.
    Look at the measurement of 85 of these mics done by cross spectrum:
    Name:  ecm8000_frequency_response_large.jpg
Views: 378
Size:  83.4 KB

  9. #9
    Senior Member pos's Avatar
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    Quote Originally Posted by Mike F View Post
    Bonjour POS,
    Oui, les microphones sont integre dans l`appareil.

    http://www.phonic.com/en/paa6.html
    super machine!

    Here are the measurements of my best matched 2405H pair, using a calibrated mic :
    Name:  406+434.jpg
Views: 641
Size:  108.3 KB

  10. #10
    Senior Member 1audiohack's Avatar
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    Quote Originally Posted by pos View Post
    There is no such thing as a generic calibration file for the ECM8000.
    Look at the measurement of 85 of these mics done by cross spectrum:
    Name:  ecm8000_frequency_response_large.jpg
Views: 378
Size:  83.4 KB

    Thats about all one could expect from a $99 retail and on sale $49 dollar mic. I sure wouldn't build a crossover or QC drivers with one. I will admit I do have three of them for use in conditions that should one get killed I could shrug it off without care.
    If we knew what the hell we were doing, we wouldn't call it research would we.

  11. #11
    Senior Member 1audiohack's Avatar
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    Quote Originally Posted by pos View Post
    super machine!

    Here are the measurements of my best matched 2405H pair, using a calibrated mic :
    Name:  406+434.jpg
Views: 641
Size:  108.3 KB
    That looks a little smoother and a bit softer on top than my measurements with a good mic with a loaded calibration file. On axis 1meter? What power?

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

  12. #12
    Senior Member pos's Avatar
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    This is the smoothest and best matching pair among a batch of 6 brand new 2405HPL drivers.

    measurement conditions are as follow:
    - ~1m distance (not precisely measured)
    - gating around 2khz
    - unbaffled 2405, siting on top of a 4412
    - FIR brickwall HP filter at 7khz
    - unknown but low SPL leval
    - calibrated Dayton mic from cross spectrum (should be good within 1dB up to 20khz)
    - calibrated tascam 144mk2 sound card

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