How bad is .2% THD

Discussion in 'Archived Threads 2001-2004' started by Norman L, May 28, 2002.

  1. Norman L

    Norman L Second Unit

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    The Pioneer 811S is rated with .2% THD

    How bad is .2% THD?

    Do you hear distortion at only high volume?

    Do you hear hiss at high volume or moderate volume?
     
  2. Aslam Imran

    Aslam Imran Second Unit

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    You wouldn't be able to hear it. Thats how bad it is.
     
  3. ThomasL

    ThomasL Supporting Actor

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    Norman, I've wondered the same thing. When I put my ear up to my front speakers with no source playing and in cd mode, I can hear a slight hiss. I don't know if this is related to the THD rating or not. I thought I remember someone in another thread awhile ago said that they read that the human ear can't distinguish THD below 2 percent. This is from the Yamaha FAQ page in the general questions section
    http://www.yamaha.com/yec/customer/f...ral/faq13b.htm
    and seems to confirm this:
    "The THD spec stands for Total Harmonic Distortion. This
    is the amount of distortion the amplifier will introduce into the original signal. Any high quality amp made today has extremely low distortion ratings. The human ear cannot
    hear anything under 2%. For the most part, when you are
    considering purchasing an amplifier, you can disregard
    the THD specifications."
    cheers,
    --tom
     
  4. AntonS

    AntonS Stunt Coordinator

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    THD is not a hiss. It's how much 2nd and 3rd harmonics is introduced into the sound. For example, if you play a single 1kHz tone (a sine wave), you are supposed to listen (and see with spectrum analyzer on the outputs) only this tone. Instead, when THD is high, on the outputs you will see the 1kHz tone plus 2hHz, 3Khz, 4kHz, 6kHz tones - these are called harmonics. The energy of these harmonics is much smaller than that of the main tone, but if they are too big you'll actually hear that the sound is "colored". So the higher is the THD, the more unnecessary coloration is introduced into the sounds.
     
  5. Ferran Mazzanti

    Ferran Mazzanti Stunt Coordinator

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    AntonS,
    that's perfectly right. Harmonic distortion is exactly what you say, but what's under the question here is what's the lowest THD the human ear can notice. That's something that honetly I don0t know, 'cause I've heard many times that long ago (in the 60's and 70's) a THD of about 0.1 was considered to be extraordinarily good, while other people say that 0.1 is really horrible. I do believe that 0.1 (and 0.2) is certainly unnoticeable, and that you'll first notice other defficiencies in the unit rather than that, but I can't tell for sure... Furthermore, I do believe that you *might* notice the effect of high THD while listening to pure sinusoidal waves, which you never do! We all hear music and movies, and that far from being a single and pure Fourier mode...
     
  6. AntonS

    AntonS Stunt Coordinator

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    I cannot come up with the actual number when the harmonics begin to be audible. I'd say >1%-2%. 0.2% is not audible by itself, but the bad thing about harmonics is that they add up. If something else in the system also introduces a lot of harmonisc (CD player, speakers), then in the end you may have pretty high THD and the sound may become muddy. So generally you don't want to have too many equipment in a chain with high THDs.
     
  7. Ferran Mazzanti

    Ferran Mazzanti Stunt Coordinator

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    Oh, I never come to think that. Could you please clarify a little bit more? You say you should not put too many equipment in a chain because that make THD increase... what do you mean exactly? Receivers are though to allow for lots of different units connected to it, but I would say you only use one thing at a time (besides the speakers): the CD when listening to music, the DVD when watching movies, etc...
     
  8. Mark Tranchant

    Mark Tranchant Stunt Coordinator

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    The Total Harmonic Distortion (sum of all the harmonics) is also not a very good measure of perceived distortion. Even-order harmonics, especially powers of two, are much "warmer" sounding than the harsher odd-order harmonics.

    The second harmonic is an octave above the fundamental, and blends in fairly well. The human brain can tolerate very high levels of 2HD, which is why valve amps get away with monstrous THD figures - it's mostly 2HD.

    The third harmonic is an octave-and-fifth, which doesn't sound too bad on top of a single sine wave tone, but sounds awful when applied to a complex signal. Solid-state amps tend to produce odd-order HD, which is why you see such small figures quoted.

    However, 0.2% THD, even if entirely 3HD, is unlikely to be perceived as distortion. It may affect the overall sound quality perception though.

    Note that hiss and hum are noise, and not harmonic distortion. HD is distortion derived from the input signal.
     
  9. Aslam Imran

    Aslam Imran Second Unit

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    Even musical instruments have harmonic distortion but its all even ordered. Thats the reason 2HD from tube gear blends nicely with the music as the brain can't distinguish it from the fundamental note. OTOH odd order distortion is audible to the brain even in small amounts as it is perceived by the brain as harshness.

    I am wondering if one were to grow up never listening to real instruments and only to ss Bose gear (with incredible odd order distortion that never gets quoted in their spec sheets), would his/her brain be accustomed to odd order distortion so when he listens to Bose gear he finds it warm and rich? Would he then percieve tube gear as 'harsh' sounding?

    Just curious.
     
  10. AntonS

    AntonS Stunt Coordinator

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    Ferran, what I mean in chain is that if you have your CD player with high THD (let's say 0.3%) hooked to a receiver that adds 0.2% and then maybe you have an equalizer with 0.2% (it's 0.7% already) and then your speaker drivers add more, then you may be in trouble. Especially if they all add a lot of odd harmonics.

    Btw, music is based on harmonics. Musical chords are basically harmonics of the main tone. Every instrument produces tons of harmonics. Human voice is full of harmonics. Thats why they sound so different and so good. But they are all "good" harmonics, as was mentioned earlier. THD spec has to be strict on mostly "bad" (odd) harnmonics.
     
  11. Norman L

    Norman L Second Unit

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    Aslam, Anton

    Is it reason not to buy a receiver at $300 with all the bells and whistles 6.1, preouts, etc due to the .2% THD?
    or is it not that important for a bedroom HT setup.
    95% Movies and TV / 5% Music
     
  12. Saurav

    Saurav Cinematographer

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    Has anyone ever wondered why no speaker manufacturer lists THD specs? The distortion numbers of speakers are so much worse than any other component in the signal chain, and simple things like placement and room damping make such a difference in the sound, that I really don't see how a difference between .2% and .1% THD would be audible in a normal listening room. Of course, some people just need to have gear with good numbers, and in that case .2% THD is twice as bad as .1% THD, and anything above .01% is intolerable anyway.
     
  13. Aslam Imran

    Aslam Imran Second Unit

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  14. Larry B

    Larry B Screenwriter

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    Aslam:

     
  15. Saurav

    Saurav Cinematographer

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    Hm, I was wondering if I should have said "almost no manufacturer". So the Nautilus 800 has an order of magnitude more distortion than a budget receiver. And how much do those speakers cost again? [​IMG]
     
  16. Samuel Des

    Samuel Des Supporting Actor

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    So is the Signal to Noise ration the measure of the "silent hiss?" i.e., the hiss that one hears when there is no source playing?
     
  17. Saurav

    Saurav Cinematographer

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    It's the closest measure, yes. AFAIK.
     
  18. John Kotches

    John Kotches Cinematographer

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    Aslam,

    You said this:
     
  19. Larry B

    Larry B Screenwriter

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    Saurav:

     
  20. Michael R Price

    Michael R Price Screenwriter

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    I think most speakers except horns and very large direct-radiators usually produce embarrasingly high amounts of THD and IMD, several percent I think I read somewhere. (If anyone has actual numbers, I'm quite curious.) Don't worry about the THD of your electronics.
     

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