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Thread: Heil with a JBL woofer

  1. #106
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    What are people doing about the rear wave and what was done in other simulations? Is the elevated distortion at lower frequency possibly due to rear wave cancellation/destruction?

    Would a set of "wings" help?

    http://www.enjoythemusic.com/diy/121..._amt1_horn.htm

  2. #107
    Senior Member jmpsmash's Avatar
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    Dispersion measurement. Not bad. By the time it got to 50 degrees, the microphone can no longer "see" the diaphragm directly.

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  3. #108
    Senior Member jmpsmash's Avatar
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    Distortion. Looks quite good from 900Hz and probably can go down to 800Hz.
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  4. #109
    Senior Member jmpsmash's Avatar
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    Comparison of my 2 Heil AMT's. They are produced on the same day, consecutive serial numbers.

    Note the scale. They are within 2dB of each other without large deviation in overall shape.

    The distortion from the green one is higher, around 2-3dB. REW doesn't seem to have a way to overlay the distortion on the same graph.


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  5. #110
    Senior Member jmpsmash's Avatar
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    Phase measurements, comparing the 2 units.

    Here is the weird one. And I have double checked the wiring and double checked the measurement. If I wire the positive to blue, and negative to brown, the same way on both drivers, they are 180 out of phase!

    After I flip the pos/neg on one of them, the phase is completely in sync again. WTF?

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  6. #111
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    Quote Originally Posted by jmpsmash View Post
    Phase measurements, comparing the 2 units.

    Here is the weird one. And I have double checked the wiring and double checked the measurement. If I wire the positive to blue, and negative to brown, the same way on both drivers, they are 180 out of phase!

    After I flip the pos/neg on one of them, the phase is completely in sync again. WTF?

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    Got a compass???

  7. #112
    Senior Member jmpsmash's Avatar
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    Quote Originally Posted by toddalin View Post
    Got a compass???
    Are you saying, since it is a symmetrical dipole, just point it backwards?

  8. #113
    Senior Member jmpsmash's Avatar
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    Impulse response comparison. The wires are flipped, confirmedName:  100126-Heil-Phase-fiipped.png
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  9. #114
    Administrator Robh3606's Avatar
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    That's odd! Well at least you know. Here is a distortion measurement I did a while back. It's overall THD Sine Sweep.

    Rob
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    "I could be arguing in my spare time"

  10. #115
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    Quote Originally Posted by Robh3606 View Post
    That's odd! Well at least you know. Here is a distortion measurement I did a while back. It's overall THD Sine Sweep.

    Rob

    Really, there's not much odd here about any of the preceding distortion measurements.

    Your measurement ( at 110db ) indicates over 3% which is in line with the other measurements ( yours is higher since it's done at a louder level ) .

    Distortion Conversions


  11. #116
    Senior Member jmpsmash's Avatar
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    Quote Originally Posted by Earl K View Post
    Really, there's not much odd here about any of the preceding distortion measurements.

    Your measurement ( at 110db ) indicates over 3% which is in line with the other measurements ( yours is higher since it's done at a louder level ) .

    Distortion Conversions

    110dB is crazy high. I am measuring at ~80-90dB. My family won't talk to me anymore and that's not just because I am wearing earplugs!

  12. #117
    Administrator Robh3606's Avatar
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    That is not a 1 meter measurement but yes it was loud as hell and worst case. I would never listen to them at anywhere near that at average levels. I am about an 85db - 90db listener depending on the source material.

    Rob
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  13. #118
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    Quote Originally Posted by Earl K View Post
    Hi "D"

    I'd suggest displaying only the 2nd, 3rd & 5th harmonics as seen in the following pic ( clipped from the previously mentioned german pdf article highlighting these AMT's ).

    Attachment 85731

    I also believe your measured distortion numbers would be a lot more comparable ( to what's seen immediately above ) if you measured at 90db ( at 1 meter distance ) like the magazine did.

    ( Just saying > measuring at 1/2 a meter at 2.83 volts will naturally jack-up the distortion readings ! )

    Duly noted - I'll take additional measurements at 90db and will show 2nd, 3rd, and 5th.

  14. #119
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    Quote Originally Posted by jmpsmash View Post
    110dB is crazy high. I am measuring at ~80-90dB. My family won't talk to me anymore and that's not just because I am wearing earplugs!
    Is the 80-90db at 1m?

  15. #120
    Senior Member jmpsmash's Avatar
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    Quote Originally Posted by dkalsi View Post
    Is the 80-90db at 1m?
    2 feet.

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