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INTRODUCTION - PLEASE READ FIRST TO UNDERSTAND THIS FORUM!

"This Harbeth User Group (HUG) is the Manufacturer's own managed forum dedicated to natural sound from microphone to ear, achievable by recognising and controlling the numerous confounding variables that exist along the audio chain. The Harbeth designer's objective is to make loudspeakers that contribute little of themselves to the music passing through them.

Identifying system components for their sonic neutrality should logically proceed from the interpretation and analysis of their technical, objective performance. Deviations from a flat frequency response at any point along the signal chain from microphone to ear is likely to give an audible sonic personality to the system at your ear; this includes the significant contribution of the listening room itself. To accurately reproduce the recorded sound as Harbeth speakers are designed to do, you would be best advised to select system components (sources, electronics, cables and so on) that do not color the sound before it reaches the speakers.

For example, the design of and interaction between the hifi amplifier and its speaker load can and will alter the sound balance of what you hear. This may or may not be what you wish to achieve, but any deviation from a flat response is a step away from a truly neutral system. HUG has extensively discussed amplifiers and the methods for seeking the most objectively neutral among a plethora of product choices.

HUG specialises in making complex technical matters simple to understand, getting at the repeatable facts in a post-truth environment where objectivity is increasingly ridiculed. With our heritage of natural sound and pragmatic design, HUG is not the best place to discuss non-Harbeth audio components selected, knowingly or not, to introduce a significantly personalised system sound. For that you should do your own research and above all, make the effort to visit an Authorised Dealer and listen to your music at your loudness on your loudspeakers through the various offerings there. There is really no on-line substitute for time invested in a dealer's showroom because 'tuning' your system to taste is such a highly personal matter. Our overall objective here is to empower readers to make the factually best procurement decisions in the interests of lifelike music at home.

Please consider carefully how much you should rely upon and be influenced by the subjective opinions of strangers. Their hearing acuity and taste will be different to yours, as will be their motives and budget, their listening distance, loudness and room treatment, not necessarily leading to appropriate equipment selection and listening satisfaction for you. Always keep in mind that without basic test equipment, subjective opinions will reign unchallenged. With test equipment, universal facts and truths are exposed.

If some of the science behind faithfully reproducing the sound intended by the composer, score, conductor and musicians over Harbeth speakers is your thing, this forum has been helping with that since 2006. If you just want to share your opinions and photos with others then the unrelated Harbeth Speakers Facebook page http://bit.ly/2FEgoAy may be for you. Either way, welcome to the world of Harbeth!"


Feb. 2018
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Low volume listening

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  • Low volume listening

    Discussing elsewhere the issue with certain music that is difficult to listen through at the same volume setting (Mahler 1, Shostakovich 2 etc.), reminded me that the reason why I bought Harbeth is because they sound so good at low levels, in that sound retains dynamics and structure, rather than sounding like a pocket transistor radio.

    If you google, this is a widespread view, particularly with P3ESR.

    I think there is some distinction in that the P3ESR is a near field speaker that has an uncanny ability to fill a medium sized room, whereas that SHL5+ (and presumably M30.1) is a speaker for a mid size room that does quiet really well.

    Are there basic and easy to understand reasons why this is the case?

  • #2
    This is a very interesting point and I too would appreciate more knowledge on this area.

    Over the years, I've always heard (no pun intended) it mentioned that the ability to do low volume in a satisfactory manner was with regards to amplifiers although I was never convinced myself as to why this would be the case.

    However, I do agree that Harbeth speakers work exceptionally well at lower volume levels and maintain a very good balance of frequencies. Simple as it may seem, and I'm not competent enough in these matters to know any more, I can only put this down to the Harbeth presenting a benign, easy to drive load to the amplifier and getting enough 'juice' from the amp at the selected volume level.

    Comment


    • #3
      The reality of 'low level sounds'

      In my opinion, anything you may have read about 'doing low levels satifactorily ' as being an amplifier issue is wrong at best and downright mischievous more likely. It just doesn't stand up to scrutiny although, as with most issues in the mysterious and invisible world of audio, there is a real issue, and a wrong explanation.

      For the amplifier to be involved in treating low frequencies differently from high frequencies, there would have to be some gross signal non-linearity, and that would be extremely easy to detect with an input/output ramp test and low cost audio test equipment (say, < GBP1000). It's such a basic test that it would be hard to imagine that any professional audio electronics designer and manufacturer anywhere on earth wouldn't be aiming for a perfecly straight-line ramp (a precursor to the device being a high fidelity unit) , undless he was designing a signal compressor for use in FM radio transmission, or a hightculb disco pa system, or a device for maximising the punch of a rock group performance, (in which case he would have good reason to make the ramp not a straight line, at 45 degrees to horizontal).

      You can see from this application video of the well-regarded Lindos test box just such a ramp test. Any audio device could be comprehensively tested in just a few seconds, as shown in the Lindos video. It isn't rocket science: it's fully automated.

      The explanation of the ramp "headroom test" is from about 3 mins in. Here. Watch to the end if you can and you'll see a set of measurements which well describe the audio equipment (amp, digital device etc.) to the point that the trained eye can anticipate how such a device would sound.

      So, if it isn't the amp (and I'm 100% certain about that), what is it then?

      Clue: ISO226 - beacause as a speaker designer I read and understood it's implications 30 years ago ...
      Alan A. Shaw
      Designer, owner
      Harbeth Audio UK

      Comment


      • #4
        Does this article by Benchmark Audio shed any light, at least on one aspect of this? Obviously it's marketing copy, but Benchmark seem fairly engineering driven, e.g.:

        > "Using a double-blind ABX test, we verified that there was a clearly audible difference when the amplifiers drove speakers at an output level of 0.01 watt."

        In Benchmark's listening room we recently demonstrated the importance of the first watt using two 100 watt stereo power amplifiers. One amplifier was a traditio

        Comment


        • #5
          It's a very human assumption to read more than intended in a statement, even one that is engineering based. One wants to believe so that one is carried along with the rhetoric. As a commercial person, I am well aware that in practically every subject one has to stop short of a full and frank disclosure of the entire, complete facts, because they could empower ones competitors. So, in the statement above, what jumps out to me is what is not actually stated. There is not a product created by man that is in every conceivable way perfect. The art of the communicator then is to highlight the ups and avoid the downs. Of course, if those downsides are significant, they cannot be hidden: the consumer will find them and the game is over.

          Can you see what that is? I have no reason whatever to doubt the integrity of the statement, but we have a long history here of awareness of AB testing.

          Anyway, I really don't think that what is being discussed is the purity (i.e. freedom of distortion) but the perceived spectral sonic balance, a totally different issue and in no way related to the first watt or even tenth watt.

          Again: hunting for differences, especially when a nice graphic makes an impact - even in not one consumer in 10,000 can explain even approximately what the mage shows, is the art of the audio marketeer. For that reason, Harbeth chooses to promote the hard way: no attractive technical graphics in our marketing and trying to use words to convey technical points. Like this post.
          Alan A. Shaw
          Designer, owner
          Harbeth Audio UK

          Comment


          • #6
            Originally posted by A.S. View Post

            So, if it isn't the amp (and I'm 100% certain about that), what is it then?

            Clue: ISO226 - beacause as a speaker designer I read and understood it's implications 30 years ago ...
            It can only be that because the ear is not equally sensitive to all frequencies at all volume levels, which means that a speaker must have a specific reply loudness level (or range) at which it will sound most balanced and natural. I expect that Harbeths are made so that they sound full and balanced at lower replay levels than are most competing speakers, which usually demand to be played louder.

            Comment


            • #7
              Originally posted by EricW View Post

              It can only be that because the ear is not equally sensitive to all frequencies at all volume levels, which means that a speaker must have a specific reply loudness level (or range) at which it will sound most balanced and natural. I expect that Harbeths are made so that they sound full and balanced at lower replay levels than are most competing speakers, which usually demand to be played louder.
              Hello Eric. I would have expected that most audiophiles if asked to draw the sensitivity curve of the ear would draw a flat line of dB versus frequency. The truth couldn't be further from that. At no frequency, at no loudness is the ear's sensitivity anything remotely like a flat line. Just take a look at 100 plus years of study of the ear, boiled down into an ISO standard.

              If you want a shock, look at the reality of the human ear's sensitivity, and compare that with the relative perfect flatness of a supermarket all-in-one micro system's performance. $50 wins. ISO Here.

              So, let's run with this a bit further as we hunt for an explanation over why Harbeth speaker sound so very different to many others. Those are not marketing words, they are for visitors to put to the test in their local store or come and make direct room-by-room comparisons at Bristol next month. The longer the listen, the better the recording, the cleaner the Harbeth sound and the greater the contrast. The fact is that as the designer I am well aware of how the ear perceives sound and consequently I work with the ear, not relying on a theoretical laboratory design of speaker.

              So, to interpret those wiggly red lines on the ISO226 curves. Along the bottom we see the usual low frequencies to high frequencies scale we're familiar with when we see 'frequency response' curves for audio equipment. Let's compare.
              .
              1. Here you can download a technical review of the SHL5plus speaker. The link to the downloadable PDF is in blue text to the left of the woofer cone in the picture of the SHL5plus. Once downloaded, go to page 5/7, Fig.1. You see the nice smooth frequency response with a horizontal axis from 20Hz to 40,000 (40kHz). Keep that browser window open

              2. Open a new browser window, then again go again to the ISO226 from above, here (or re-view the first visit there if that window is still open)

              3. Hopefully you have the SHL5plus curve and the ISO226 open in two side by side browsers now. Make an allowance for the fact that the ISO horizontal scale is 16Hz to 16kHz, and the SHL5plus graph is 20Hz to the much higher 40kHz (over twice as wide a bandwidth as the ISO curves).

              4. Now, look at the SHL5plus curve in Fig1, and run your eye over the the left vertical scale and see that it generally aligns with about the 90dB line (approximately)


              Agree so far?

              5. Now look again at the ISO226 curve and look for the 90dB line on the left vertical axis .... it's easier to look in the middle of the graph left - right to see a stack of phon numbers marked 'minimum level' to '100 phon' and see that there is one set of curves at 80 phon and another at 100. So the 90dB test frequency response used for the SHL5plus must be a loudness level which lies half way between these two. Run your eye left to see that that imaginary midway point would align with the 90dB vertical scale.

              6. Now, note that the exact shape of the 80dB and 100dB lines are not quite the same, but there is not much difference between them. In contrast, the curve lines down at 20 phon are markedly different, becoming less so as the dB level progressively increases.




              That's a very important point, but there are other more subtle and more critical to this discussion. Any suggestions?

              Oh, one vital thing I have not mentioned is that the ISO curves are presented in the inverse way to that which we hifi people normally think, and you have to make a mental allowance for that. These curves show equal loudness, that is, a sensory experience to a human listener. In other words, how loud sounds had to be, relative to 1kHz, for the listener to say that they are perceptually equally loud relative to 1kHz. To think of the ear's characteristics as conventional equipment frequency response charts you have to flip the ISO curve set vertically.

              Every trace is normalised to 1kHz at various loudnesses. (Read that again: it took me years to properly grasp that).

              See what beautiful picture they paint of the ear and the traps for the unwary speaker designer? Even a rudimentary understanding of this is of paramount importance in the selection, critiquing and listening satisfaction to hifi equipment.
              Alan A. Shaw
              Designer, owner
              Harbeth Audio UK

              Comment


              • #8
                Alan, the link in your numbered paragraph 1 seems to be the same document as the others, i.e. to the ISO 226 document - don't think this is what you intended?

                Comment


                • #9
                  That article is pseudo-science, as every engineering student can tell after a basic course of control systems theory.

                  The test is also flawed. First of all, we don’t know anything about the other reference, then using a single steady tone is misleading: with real music, even at low loudness levels, that (supposed) difference of distortion would be completely masqued to a human ear by other parts of useful signal.

                  Comment


                  • #10
                    International Organization for Standardization - "When the world agrees"

                    Originally posted by Nessuno View Post
                    That article is pseudo-science, as every engineering student can tell after a basic course of control systems theory.

                    The test is also flawed. First of all, we don’t know anything about the other reference, then using a single steady tone is misleading: with real music, even at low loudness levels, that (supposed) difference of distortion would be completely masqued to a human ear by other parts of useful signal.
                    I'm sorry but we are indeed dealing with recognised facts so I'm not going to debate this with you. The International Standards Organisation (ISO) are empowered by the world to represent the best that science can offer in the understanding and regulation of our bodies and environment. ISO standards are thoroughly vetted and peer reviewed. They represent the ultimate in human knowledge.

                    The small all print of the precise conditions under which a standard can apply and so on are properly defined, as you would expect, as are caveats concerning use. I chose to link to a third party site for a single-page overview of the ISO standard, but you can look it up on the ISO website, here. Payment of Swiss Francs 88 is required to download it. It was technically reviewed and reauthorised as recently as 2014.

                    As with all research work in any field, it is imperfect. The skill is to recognise and work within limitations and apply common sense in interpretation. For our purposes, common sense validates the hearing acuity curves, known since the 1920s and subtly revised since.

                    An overview of the entire hearing acuity matter is here on the Lindos site, here
                    Alan A. Shaw
                    Designer, owner
                    Harbeth Audio UK

                    Comment


                    • #11
                      Many thanks to those eagle-eyed readers: links fixed.

                      It's amazing: one goes to bed thinking over a subject that one is in outline familiar with, and at 4am the subconscious wakes you with a hitherto unseen connection between matters!

                      I suspect the biggest difficulty with this so far is the mental ability to flip the ISO 226 chart vertically, to make it more recognisable to those who appreciate audio equipment frequency responses. I'm preparing that now.
                      Alan A. Shaw
                      Designer, owner
                      Harbeth Audio UK

                      Comment


                      • #12
                        Originally posted by Nessuno View Post
                        ...then using a single steady tone is misleading: with real music, even at low loudness levels, that (supposed) difference of distortion would be completely masked to a human ear by other parts of useful signal.
                        I know where you're coming from, but I think that there are many instances of "real music" that make use of steady tones. Those steady tones might have other harmonics added to them to make them more musically palatable, but there is still an underlying steady tone sitting there for everyone to hear. Isn't that what synthesisers are good at doing, and they are a popular instrument amongst many musicians who have learnt how to use their programmability to generate new and novel sounds (e.g. Rick Wakeman, Greg Lake, Jean Michel Jarre, Richard Wright, to name but a few that I know of; there must be many others). Therefore, if an amplifier generates 1% distortion on a steady tone at low power output levels, then this would detract from the quality and accuracy of the reproduced sound, at least if one plays that type of music at such low power output levels.

                        Comment


                        • #13
                          I stress - we are NOT focusing in this thread on DISTORTION, neither low level nor high level. Distortion is not relevant to this thread at all. Explore that in another thread by all means.

                          We are focusing on spectral balance: low, mid and high frequencies. Let's keep to the core subject or this, like so many threads before it, will dry up before the matter can be adequately explored.
                          Alan A. Shaw
                          Designer, owner
                          Harbeth Audio UK

                          Comment


                          • #14
                            OK, to make the ISO226 curves a little more manageable, I've coloured the ones that are relevant to our normal listening level experience of hearing music. Much more on that innocuous little sentence later.

                            Click image for larger versionName:	HUG AAS AA ISO 260 colour.jpgViews:	1Size:	191.3 KBID:	75470






                            Sound levels marked on the left vertical scale below, say, 50dB, are those that would be found in an office, and are really too low to be of interest to us listening to music at even a moderate level at home. There, depending upon amplifier power, speaker efficiency, listening distance, music type, recording, taste, neighbours, room absorption, time of day and so on, we may typically be listening in the 70-100dB range.

                            I stringly recommend spending time just looking at this chart, even with no understanding of the technical back. What they tell us is that the sensitivity across the audio band of the ear is directly correlated with how loud the sound is. If that were not the case, every one of those coloured and grey lines would be a perfectly flat horizontal line from left (low freq.) to right (high freq.), exactly as you would expect for a hifi amplifier.

                            Make sense?

                            Now I'll manipulate the curves a bit.
                            Alan A. Shaw
                            Designer, owner
                            Harbeth Audio UK

                            Comment


                            • #15
                              Originally posted by A.S. View Post
                              ISO standards are thoroughly vetted and peer reviewed. They represent the ultimate in human knowledge.
                              Sorry, my bad: I was of course referring to the article linked from the Bemchmark site, in which technical terms are used in a quite fictional way.

                              For the very reason quoted above the idea of telling an ISO paper “pseudo-science” couldn’t ever have crossed my mind. Not in the least!

                              Comment

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