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Gradient Absolute Listening Test

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  • Tom Mallin
    The description of the Gradient Absolute Listening Test developed by Gradient designer Jorma Salmi has not easily been available on current internet pages for
    Message 1 of 4 , Jun 5, 2014
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      The description of the Gradient Absolute Listening Test developed by Gradient designer Jorma Salmi has not easily been available on current internet pages for awhile.  Here is a capture from the internet archive wayback machine at https://web.archive.org/web/20060620220211/http://www.gradient.fi/design/stereo/sivu3.htm; unfortunately the graphic was not captured, but I think you can figure out the test procedure anyway:  


      THE ABSOLUTE LISTENING TEST

      At first Salmi arranged a listening test in a big anechoic room. What is an anechoic room? To put it simply it is a room without reflections i.e. reverberation, standing waves, flutter echo etc. In fact it´s a room with no acoustics at all.

      He listened to various loudspeakers on the spot where the measured frequency responses were as flat as possible (usually you can find this spot on the so called design axis).
      When listening to high quality recordings with high quality speakers he was surprised to learn how good they sounded. Here are his main findings:

      • the sound was very clean and pure
      • imaging was excellent
      • acoustics of the recording venue were reproduced excellently
      • spatial information was reproduced much better than in ordinary rooms
      • sound quality was much better than in ordinary rooms

      After listening to loudspeakers in an anechoic room Salmi arranged the so called Absolute Listening Test (ALT). It was conducted as follows:

      • the loudspeaker under test was situated inside an anechoic chamber
      • a high quality measuring microphone (B&K 4133) was placed on the design axis of the speaker
      • music program was fed to the speaker from a source (record player, microphone or tape recorder)
      • monitoring took place outside the anechoic chamber
      • by switching it was possible to detect the difference between the speaker/microphone combination and the source (a straight wire)
      • both headphones and loudspeakers were used in monitoring

      Absolute listening test

      This test produced the following rather surprising results:

      • when the frequency response curve of the test speaker measured by the microphone was flat, the listeners could not make a distinction between sounds arriving directly and those reproduced via the speaker under test
      • non-linear and phase distortion, delayed resonances and similar phenomena did not appear to have an audible effect upon the sound quality of high quality speakers
      • flat frequency response was the most important factor

      Listening to good quality recordings in an anechoic room sounded excellent. The difference between the direct sound compared to that passing through the loudspeaker and the microphone was minimal.
      At that stage Salmi decided to investigate what happens in an ordinary room. Or how your listening room kills the sound quality.

    • listentwice2002
      Was this a stereo test or performed with a single mono speaker in the anechoic room? I could not find a hint. A serious description of the setup would specify
      Message 2 of 4 , Jun 5, 2014
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        Was this a stereo test or performed with a single mono speaker in the anechoic room?
        I could not find a hint.
        A serious description of the setup would specify angle and distance between the speaker(s) and the microphone(s).
        Comparing a single speaker and the same signal from a stereo set of identic speakers creates quite some difference, beside spatial information.

        These thoughts come to my mind:
        Joachim Gerhardt and Siegfried Linkwitz try to integrate rear radiated and front energy into the room, with their dipole concepts. JG wrote about a more directional front and more diffused rear energy being helpful for a close to natural performance/reproduction.

        The Gradient approach with the citated 12" midrange (no baffle, no cabinet resonance, no edge diffraction) is no pure dipole, it looks appears to be close to JGs G-pole
        http://www.georg-stracke.eu/?p=1040
        br HM
      • Tom Mallin
        As I recall, this was a monophonic test with a single speaker in the anechoic test chamber, with the microphone aiming at the speaker on the speaker s design
        Message 3 of 4 , Jun 5, 2014
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          As I recall, this was a monophonic test with a single speaker in the anechoic test chamber, with the microphone aiming at the speaker on the speaker's design axis.  The speaker, according to REG, was a B&W 801.  

          The observed results of this test led Gradient to pursue speakers with flat frequency response which, to the maximum extent practical, ignored the listening room acoustics, simulating sound generated in an anechoic room, thus enabling them to accurately reproduce the source fed to the speakers.  This research fed into the development of Gradient speakers from the 1.3 to Revolution to 1.5.

          The 12" midrange was found on the Gradient 1.0 and 1.3.  That made especially the 1.3 an unusual looking speaker since the midrange is larger than the woofer and even seems big compared to the entire woofer cabinet.  See the picture at:  http://www.regonaudio.com/Gradients.html  The Revolution's in-room response was exceptionally flat in both REG's measurements and Stereophile's tests.  See:






          On Thu, Jun 5, 2014 at 4:26 PM, listentwice2002@... [regsaudioforum] <regsaudioforum@yahoogroups.com> wrote:
           

          Was this a stereo test or performed with a single mono speaker in the anechoic room?
          I could not find a hint.
          A serious description of the setup would specify angle and distance between the speaker(s) and the microphone(s).
          Comparing a single speaker and the same signal from a stereo set of identic speakers creates quite some difference, beside spatial information.

          These thoughts come to my mind:
          Joachim Gerhardt and Siegfried Linkwitz try to integrate rear radiated and front energy into the room, with their dipole concepts. JG wrote about a more directional front and more diffused rear energy being helpful for a close to natural performance/reproduction.

          The Gradient approach with the citated 12" midrange (no baffle, no cabinet resonance, no edge diffraction) is no pure dipole, it looks appears to be close to JGs G-pole
          http://www.georg-stracke.eu/?p=1040
          br HM


        • regtas43
          I think the point of the test was to point out--which is surely true--that many of the things that people worry about about speakers-- delayed
          Message 4 of 4 , Jun 5, 2014
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            I think the point of the test was to point out--which is surely true--that many of the things that people worry about about speakers--"delayed resonances"[Gradient's phrase], phase nonlinearities, distortion and so on --were not really important compared to room effects and indeed were not very important altogether in absolute terms. There is more on this here

            http://www.regonaudio.com/Audio%20in%20Modern%20Times.pdf

            pages 9 and 10

            This includes a diagram and quote from the (now deleted it seems) description formerly on the Gradient website.

            Strange is it not how one of the crucial, definitive experiments in the history of audio is now documented only by a secondary source on a small website, namely my own.

            Can one imagine this in say physics? That for example the Michaelson-Morley experiment could be found described only on the website of one single private individual?

            But this illustrates the difference between audio and real science, I suppose.

            This is a fundamental experiment, carried out correctly and with profound consequences. Hardly anyone has ever heard of it and even fewer people seem to take in what it means.

            Read carefully those two pages--9 and 10--over and over. Here is truth.

            REG

             


             

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