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  • Speaker THD percent, DIY compared to commercial

    I was curious how commercial offerings compared and despite some horrifying returns on investment even in the $10,000-15,000 range (cheap crossover components, electrolytics everywhere). Many European speaker manufacturers produce their own drivers and I'm wondering how their best compares.

    Based on the German site stereo.de THD measurements most TOTL commercial $10-15k offerings offer THD of (63 / 3k / 10k Hz 0.3 / 0.1 / 0.1%) and some of the crazy $20k-30k speakers offer THD of (63 / 3k / 10k Hz 0.1 %/ 0.01 / 0.01%)

    I notice that some of the speakers which use drivers such as the Scan revelators, SB satori, Accuton drivers offer THD around (63 / 3k / 10k Hz 0.4 / 0.2 / 0.2%). Of course THD is not everything and IMD, 2nd vs 3rd, higher order distortions matter more but .01% from the latest tech on these outrageously priced speakers seems impressive. Are there any DIY drivers which can compete with this spec, or is this .01% something we should expect with the next generation of DIY drivers?

  • #2
    0.01% from a speaker? I think not. Below 500Hz 1% at 1 watt is more like it, and as that's -40dB it's well below the threshold of audibility. Even 10% is -20dB. That's why 10% was picked as an acceptable definition of woofer xmax. Don't compare speaker THD to the very low levels that electronics can achieve. Electronics have very low THD because with their lack of moving parts it's very easy to realize.
    www.billfitzmaurice.com
    www.billfitzmaurice.info/forum

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    • #3
      I'm pretty sure I saw .01% somewhere but .03/.02% seems to be it. That would be -70db down right? Not sure at what output level these are taken but there are plenty of Accuton speakers and the Wilson Audio speakers have recognizable revelator and satori drivers.

      Reviews (use google translate, chrome browser)
      https://www.stereo.de/hifi-test/kate...andboxenpassiv

      Wilson Audio with Revelators
      https://www.stereo.de/hifi-test/prod...sabrina-x-1919

      Dynaudio with the lowest measurements
      https://www.stereo.de/hifi-test/prod...idence-50-1756

      Bill, I'm not understanding your comment on THD at 1 watt. Erin has a Purifi woofer review where THD is under 1% even at 100db for most of the passband. And the audioexpress measurements has the Scan 21we 50-60 db down for 2nd & 3rd harmonics at 50hz. Although there are two THD graphs and no output level is given for the .25% THD given in the bass. Is it 100-110db output like the other?

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      • #4
        Originally posted by Krillin View Post
        I notice that some of the speakers which use drivers such as the Scan revelators, SB satori, Accuton drivers offer THD around (63 / 3k / 10k Hz 0.4 / 0.2 / 0.2%). Of course THD is not everything and IMD, 2nd vs 3rd, higher order distortions matter more but .01% from the latest tech on these outrageously priced speakers seems impressive. Are there any DIY drivers which can compete with this spec, or is this .01% something we should expect with the next generation of DIY drivers?
        The ATC midrange is a 40+ year old design with distortion around -70 dB at reasonable SPLs. Neumann's modern equivalent has a similar performance. It would be more difficult to design motors to get these distortion levels with the large displacement of a woofer at reasonable SPLs but if it sold drivers in any sort of volume I expect it could be done. What advancing technology/manufacturing seems to have done more is enable modestly priced standard range drivers like those from SB Acoustics to have levels of distortion approaching those of the premium drivers.

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        • #5
          In some electronics (eg. some but not all modern DA converters) where a threshold of audibility of SINAD or THD+n can be established, and where some existing real devices can be objectively shown to be fully under that threshold, then that threshold and the device's measured performance relative to that threshold can be very useful. For if it can be shown that all of the nonlinearity is always below a threshold of perception, then that nonlinearity needs no further evaluation in its effect in the audio.

          That doesn't work for loudspeakers, because not all of a loudspeaker's nonlinearity is below threshold of audibility, so it needs further analysis and evaluation and characterization suitably weighted for the perceived degradation of the resulting sound. Among audibile nonlinearity, some forms and levels of nonlinearity are widely perceived as more offensive than others. Because of that, it has been argued (and I agree with the argument) that THD oversimplifies the characterization of nonlinearity in loudspeakers, and is a poor figure of merit in that application.

          The efforts of Earl Geddes and Lydia Lee were worthwhile in trying to establish perception weighted distortion metrics, a good foundation that could be further refined. His is sometimes a controvercial personality, and that seems to get in the way of some useful discussion topics that include discussion of his contributions to the applied science.

          http://www.gedlee.com/Papers/papers.aspx
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          of interdependent networks of trade, finance, information, law, people and governance."
          - from the October 2007 U.S. Naval capstone doctrine
          A Cooperative Strategy for 21st Century Seapower
          (a lofty notion since removed in the March 2015 revision)

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          • #6
            Originally posted by Krillin View Post
            Bill, I'm not understanding your comment on THD at 1 watt.
            THD rises with excursion, excursion rises with power. If the THD plot is measured at the same time as the SPL plot, which is typically done at 1 watt, the THD will be lower than if it was measured at higher power. As I alluded to before if a woofer is measured with sufficient power to reach xmax as per the Klippel standard THD will be 10%.

            www.billfitzmaurice.com
            www.billfitzmaurice.info/forum

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            • #7
              Shifting the conversation a bit here. Can anyone explain why audioxpress voicecoil test bench butchers so many tweeters and midwoofers in frequency response? And why so many fr sweeps by DIY'ers do not match up?

              I have seen many DIY speakers have flat frequency response. Then the voicecoil frequency response has wild swings.

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              • #8
                Krillin, it would be better to pose your question in a new post - it is a good one, and I would comment on it there.

                To the OP topic, the first challenge to measuring distortion is a quiet noise floor. Even the very best environment would be 45dB or more. This is one reason why the mic is placed so close to the driver.
                Then the mic has to be capable of loud SPL, over 120dB. This means a more expensive 1/2" capsule mic.

                Sometimes it is not so hard to actually hear distortion with your own ears, but of course more SPL means more distortion, and then you would not want to listen to such a loud level. And if you can hear it at a moderate level, you wouldn't want to use that driver in your design!

                One could make a career just from measuring distortion.
                --

                Philip Bamberg
                BambergAudio.com

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                • #9
                  Sure I will open another thread on that subject of audioexpress measurements tomorrow. As far as this distortion thread goes...

                  Revelator is at least 20 yrs old
                  Satori motor from at least 2012
                  SBacoustics motor design from late 2000's
                  Vifa NE's from at least 2011
                  Wavecor from early 2010's
                  Morel TiCW from early 2012
                  Accuton neodymium 2014?
                  Dayton Epique, accuton neodymium motor design?
                  Dayton Esoteric from late 2014

                  My point is with all the advancement in computer aided design programs is everyone aware that most designs are around ten years old? Yes, although the revelators are excellent even today, time marches on. I would just love to see them show something new with an emphasis on smooth frequency response with Purifi-like low IM distortion.


                  In the past I have advocated exotic cone materials. I still stand by that however I have noticed that smooth frequency response with no breakup is very hard to come by. I would love to see a 90db 8-ohm poly midrange cone with Audio Technology SKDM like frequency response and a 2021+ motor design. Nail a perfect design with no breakup, then afterwards add exotic cones materials when the driver has proven itself.

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                  • PEB
                    PEB commented
                    Editing a comment
                    Krillin, I agree with you. I just went browsing around for drivers the last couple of weeks, as I do every couple of years. Yawn. Always new cone materials, but as long as the motor design is solid, the driver should sound pretty good regardless. Yet prices slowly and steadily rise. The styling leaves much to be desired too IMO.

                    I am inclined to just go back to C-quenze 15cm and Scan D2904-7100, just as I use in my series 6. This is a Dynaudio like sound. IOW, boring sound at first, bc there is no artificial excitement from driver distortion, and needs to be pushed louder to sound more dynamic and transparent. But then it plays loud without strain, too. Metal cone on a good motor sounds more transparent but can sound edgy when pushed.

                    It's a fine line between resolution and forgiveness.

                • #10
                  Originally posted by Krillin View Post
                  My point is with all the advancement in computer aided design programs is everyone aware that most designs are around ten years old? Yes, although the revelators are excellent even today, time marches on.
                  The win from a better understanding of the detailed physics provided by 3D computer simulation happened years ago. Further advances will need to come from elsewhere. This better understanding of how to design motors shows up more in the rise in performance of standard range drivers rather than premium ones. That is, how to do more with less.

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                  • #11
                    Krillin,

                    Can you share a link of the TOTL speaker you're referring to?

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                    • Krillin
                      Krillin commented
                      Editing a comment
                      Post #3. Wilson Audio compared to Dynaudio Confidence 50. The measurements are not the most comprehensive but it's something.
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