Distortion measurements question

Discussion in 'Audio Science' started by Some1, Apr 17, 2019.

  1. Some1

    Some1 Rando

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    Hi, why do THD measurements never show THD above 10khz?
    I'm asking because I want to add in EQ 5db above 10khz and I've heard that it's supposed to raise THD.
     
  2. atomicbob

    atomicbob dScope Yoda

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    Q: What is the 2nd harmonic of 10 KHz?
    A: 20 KHz

    Q: What is the 3rd harmonic of 10 KHz?
    A: 30 KHz

    Q: What is the generally accepted frequency response upper limit for the human auditory system?
    A: 20 KHz
     
  3. Some1

    Some1 Rando

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    Thanks for the reply.
    So where do i see in the graph the distortion from 10khz-20khz?
    I see in purrin's THD measurements D2 D3 D4. What are those?
     
  4. purr1n

    purr1n Finding his inner redneck

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    D2 = 2nd harmonic
    D3 = 3rd harmonic
    D4 = 4th.

    In many graphs, we may not see plotted distortion from 10kHz to 20kHz. This is because these distortion components are ultrasonic - not be within the range of human hearing and may not be measured (it's good practice to limit bandwidth for measurements - another topic).
     
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  5. Thad E Ginathom

    Thad E Ginathom Friend

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    Curious about your intentions and motives. Did you just pluck a number out of the air, or do you have a reason? I may well be listening with more than +5dB starting lower than that, because without it I won't even hear that stuff. Do I get distortion as a result? Frankly, these days I wouldn't know so I don't care.

    Your ears are probably in better shape. They, rather than the theory, should be telling you if your EQ is doing what you want and whether or not it sounds good.
     
  6. Some1

    Some1 Rando

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    I saw in the FR measurements of Koss/Massdrop ESP95X that its lacking in 10-20khz about 5db (or a bit more). I also increased 8-10khz since in one measurement its also lacking.

    So it did make them brighter and more treble forward. And I dont like it. So I dont EQ anymore.

    But what really bothered me more about them is that the soundstage is too small and forward to my taste. I added cotton beneath the pads to make the driver be further away from my ears. I like the sound better now. I bet it changes FR but I dont have the equipment to see how.
     
  7. purr1n

    purr1n Finding his inner redneck

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    Measurements past 10kHz tend to be reliable and subject to radical change depending upon positioning. I'd take them with a grain of salt.

    With mods, don't worry about measurements too much. If it sounds right and achieves the goals you set forward, then that should be sufficient. If I have time I can try stuffing material under the pads and take another measurement.
     
  8. Dzerh

    Dzerh Friend

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    Sorry, what do you mean by "lacking 5db"? Compare to what?
     
  9. purr1n

    purr1n Finding his inner redneck

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