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Demonstration of the unique Harbeth RADIAL™ cone material v. other materials

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  • Demonstration of the unique Harbeth RADIAL™ cone material v. other materials

    On this thread we've been looking at the sound and physical composition of the piano. In this post, we made some excerpts from the very well made video. I've taken one spoken phrase and modified to to let you experience the 'Harbeth sound' versus the sort of dry ambient sound you'll hear on other speakers, regardless of the brand if they use vacuum formed polypropylene cones, for example.

    The RADIAL™ advantage relates to the way the Harbeth cone and cone material releases energy in the decay-to-silence after a note or word. If you can hear the difference between these two clips, you are in a position to look through your CD collection and arm yourself with nice, atmospheric recordings that have space and air around the instruments (and voices) and use those to compare speakers - and experience for yourself how unnaturally dead the reverberation tails are on other speaker system. Once you know what to listen for, all other speakers sound airless, and woolly - foggy in fact. The reverberation time in this clip is about 1 second, and I've dramaticised the effect so you can hopefully hear it. The reverberation should sound clean and bright right down to silence, not have the sparkle erased from it, as vacuum formed PP unfortunately does in the upper audio regions.

    Loading the player ...
    Clip 1 - conventional speaker, polypropylene vacuum moulded cone

    Loading the player ...
    Clip 2 - Harbeth RADIAL™ cone

    Hopefully this will reproduce on PC speakers to make the point. On real speakers the effect is much more obvious.
    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

  • #2
    What should I hear?

    I hear two 2 second clips with the words "player wouldn't have as much control"

    In Clip 2 I hear a breath at the end which is missing in clip 1.

    Is that what I should be hearing?

    Listened on HiFi:

    Caiman Dac > Quad 520f > MB Quart 980s

    Comment


    • #3
      Originally posted by Labarum View Post
      I hear two 2 second clips with the words "player wouldn't have as much control". In Clip 2 I hear a breath at the end which is missing in clip 1. Is that what I should be hearing?

      Listened on HiFi:

      Caiman Dac > Quad 520f > MB Quart 980s
      Not exactly. I appreciate the feedback: I've been living with this understanding for about 20 years and I really would like to pass on the knowledge! Once you 'get it' you'll never forget it.

      Remember this is a synthetic example, so the effect is somewhat magnified. What you should concentrate on is the tonal 'brightness' of the echo (the reverberation) from the instant he finishes the word "control" to that intake of breath. You are listening for how that energy in the world "control" fades down as it dissipates into the acoustic space of the room. Maybe I could slow down the clips.

      OK, first I'll upsample the source file, cut off the in-breath so that you are not at all confused by that. Here is the mk2 versions:

      Loading the player ...
      Clip 1B - conventional speaker, polypropylene vacuum moulded cone

      Loading the player ...
      Clip 2B - Harbeth RADIAL™ cone

      and here if I reduce the pitch by 3 semitones:

      Loading the player ...
      Clip 1C - conventional speaker, polypropylene vacuum moulded cone

      Loading the player ...
      Clip 2C - Harbeth RADIAL™ cone

      Do you hear that in the RADIAL™ examples you get a clear sense of the acoustic space in which the voice is speaking? That 'microtonal detail' is masked by music (and speech) but is exposed when the masker, the much louder music/speech signal ceases. The extra resolution of the Harbeth cone is, of course, constant throughout the music, but you become most aware of it when the music ceases.

      This point is absolutely crucial to appreciating what the RADIAL™ cone digs-out from the recording. Of course, if the recording is made in a heavily damped voice booth which has no reverberation, then the RADIAL™ cone is not going to magically create 'space' around the voice that wasn't there in the first place. I guess that a reason that vacuum formed polypropylene cones are used by the vast majority of speaker brands is because their customers are not playing real acoustic music as much as I/we do, do not attend live concerts where that 'air' is really tangible and a vital part of being there live, listen to processed pop music which has no 'air' anyway, or have set their internal reference standard of how home audio should sound somewhat below the standard we enjoy.

      What sort of recording do I think captures the piano with the 'air' that I hear in the concert hall? Before I give an example of what I think is about as good as it gets, hop over to this post (and then return) where we look at a truly astonishing characteristic of the grand piano ....
      Alan A. Shaw
      Designer, owner
      Harbeth Audio UK

      Comment


      • #4
        Hopefully you've dipped into the piano thread - now let's pull this all together.

        What we're trying to do - assuming that the recording actually contains ambient information - is to get it our through the heavy, inert, speaker cones and radiating into the room to generate that light, airy clarity that surrounds a real concert piano in a rehall. Crucially, we want to capture that tonal brilliance that is exposed when the performer lifts his fingers of the keys, the energy input ceases, and the piano sings, radiating the energy for minutes afterwards.

        Loading the player ...
        Clip 3: Graham Fitkin, Aract (highly recommended).
        Makes me want to weep every time I hear those beats in the decay down to silence.

        Another example, Gulda. Actually, I used this CD to design the original Compact (in 1987?) and it was the first time I really appreciated how important the speaker cone material is to final sound. I could hear 'air' around the notes which were smothered to inaudibility on the vacuum former polypropylene cones of the very best BBC monitors of the time. It's nice to hear this track again. I'd be very surprised if this is a Steinway.

        Loading the player ...
        Clip 4: Gulda own composition I think (highly recommended).

        Another example of the inter-note air and sense of space around the piano (lovely)

        Loading the player ...
        Clip 5: Rachmaninov, Lief Ove Andsnes (highly recommended). We are in no doubt with this recording that it is live and in a large hall. We should aim to capture the air that the audience would have relished.

        Loading the player ...
        Clip 6: Guastavino (lovely) - reverb possibly electronic?

        Loading the player ...
        Clip 7: A recording I made at Fairfield Halls, no audience, Steinway D, B&K omni mics to DAT. A real sense of space.

        I better stop now. There is something about that slow-beat in the decay between the notes which really touches me deeply.
        Alan A. Shaw
        Designer, owner
        Harbeth Audio UK

        Comment


        • #5
          What I hear

          Originally posted by Labarum View Post
          I hear two 2 second clips with the words "player wouldn't have as much control"

          In Clip 2 I hear a breath at the end which is missing in clip 1.

          Is that what I should be hearing?
          What is hear is that on clip 1 there's a bit of reverb that surrounds the voice while it's speaking, but as soon as the voice stops, the reverb dies to nothing.

          On clip 2, the reverb is still alive even after the voice stops; there's still energy circulating in the room.

          Comment


          • #6
            Dry v. wet acoustics

            Originally posted by EricW View Post
            What is hear is that on clip 1 there's a bit of reverb that surrounds the voice while it's speaking, but as soon as the voice stops, the reverb dies to nothing.

            On clip 2, the reverb is still alive even after the voice stops; there's still energy circulating in the room.
            That's it. That's the effect I'm trying to demonstrate.

            Studio engineers talk about reverberation in terms of dryness and wetness. A recording made in an anechoic chamber (not that one would record music in such a dead acoustic) would be 100% 'dry'. A recording made in an all-glass space such as the Louvre pyramid where there is no absorption and the echo would bounce around for ages, would be considered 100% 'wet'*. All normal concert halls fall somewhere along the line between completely dry and completely wet, and getting the reverberation just right is a very specialist matter because, when optimised, it adds air, clarity and loudness to the performance. If ouir aim is to reproduce the magic of the hall, we don't want the loudspeaker to modify the acoustic around the performers, to throw a woollen blanket over the walls of the venue to suppress the natural reverberation.

            So, as you have identified, what I am attempting to illuminate (by synthesis) is that the vacuum formed polypropylene cone itself dries out the ambient microtones in the recording (assuming they are there) that passes through it. This is because polypropylene is not free to release those exceedingly low-energy details as sound; the molecular structure in waxy polypropylene is such that the molecules slide over each other when there is a small energy input from the voice coils, as in the case of low-level details, and that generates friction heat in the material, not sound. Once the voice coil micro-motion is exchanged for heat in the cone, it is impossible to hear those sounds; heat cannot be converted into sound. During normal western music performance, the high level sounds drown out or mask all low level details and we are carried along with the melody, the harmonies are of lesser importance. But between the notes, when the instrument contributions are permitted to naturally decay (there must be an Italian word for that!) the heat exchanging effect of polyproylene takes over and the sonic microtonal details evaporate.

            *I've not been to the Louvre pyramid, and the glass walls are not parallel but at angles to each other. It may be that the acoustics are less wet than an all-glass structure would suggest. This is just an illustration.
            Alan A. Shaw
            Designer, owner
            Harbeth Audio UK

            Comment


            • #7
              The 'air'

              Thank you, Alan. I have never listened for that decay in a speech recording before. I now hear it clearly in your demo clip.

              Piano? Ah yes. The the air around the instrument - a combination of the hall acoustics and the natural decay of the strings exploited by the skilful use of the damper pedal by the pianist. I will send to you at your business email address a FLAC of my favourite piano track

              Choralvorspiel "Nun komm' der Heiden Heiland" BWV 659
              Bach: The Italian Concerto; Chromatic Fantasy (1976)
              Brendel, Alfred

              This is from an old AAD CD, but it catches the "air" so well. I wonder if it would have been even better if the original had been a digital recording with a lower noise floor.

              I am still thinking about your piano clips. The problem is that the "air" is the first thing to go as you move from a lossless format like FLAC to a lossy format like MP3 or AAC. The lower the bitrate the more the "air" gets lost. It is remarkably difficult to tell a lossless file apart from a high bitrate lossy file, but you have to listen very hard around the edges of the music. So I am wondering what I am listening to and for on your Pno clips.

              My MB Quarts have two 8" paper woofers each, and aluminium dome for the mid from 300Hz up and a titanium tweeter. An audio-pro once described them to me as "Rogers on steroids". Rogers used the MB Quart titanium tweeter in some of their models. All by-the-by, I had thought the "air" was down to good bass extension capturing the ambience of the hall. (It is sometimes disconcerting to hear the hall aircon rumble!) But maybe I'm wrong about "air" and bass extension?

              And I really must hear some Harbeths sometime, but I not a box swapper - I listen to music. I come to this site for decent discussions such as this.

              FLAC follows shortly. I would be interested in your opinion, and maybe even an illustrative clip from the FLAC, though I fear transcoding to MP3 will loose a bit of the "air".

              Comment


              • #8
                Bass frequencies responsibe for 'air'? - No

                Originally posted by Labarum View Post
                Piano? Ah yes. The the air around the instrument - a combination of the hall acoustics and the natural decay of the strings exploited by the skilful use of the damper pedal by the pianist. I am still thinking about your piano clips. The problem is that the "air" is the first thing to go as you move from a lossless format like FLAC to a lossy format like MP3 or AAC... I had thought the "air" was down to good bass extension capturing the ambience of the hall. (It is sometimes disconcerting to hear the hall aircon rumble!) But maybe I'm wrong about "air" and bass extension?...
                You are absolutely correct that a lossy bit-reduction system like MP3 works by discarding detail that is masked by louder sounds. There really is no other viable strategy to retain approximately the same overall fidelity but use less data. And yes, just presenting these examples as (high bitrate) MP3 here implies that microdetails have been erased in the WAV>MP3 conversion.

                However, we are listening for the 'air' in the decay between the notes and after the notes are struck. In these special situations, the MP3 encoder can give much more attention to retaining the low-level information because it is somewhat freed-up from heavy number crunching when the music is loud. So, for just one pass WAV>MP3, enough detail remains in the reverberation tail to make the examples valid enough if not perfect. Did you see the thread about multi-pass MP3 (where?) where I made audio examples of exactly what is lost during successive encode/decode/re-encode cycles?

                No - 'air' does not relate at all to the low frequencies contained in the hall or the recording. It's not 'air' as in air conditioning or 'air' as in stifling hot or 'air' as in a draught. That's an entirely separate but parallel issue. Perhaps a better word would be 'presence', but that's not quite right because it suggests some sort of projection of sound, which this isn't. Or 'inner sparkle'? The enveloping recording atmosphere in the lower registers I think you're referring to is indeed a vital part of the overall feeling of 'being there' and has much to do with the selection of microphone types. The Peter Grimes thread is a good example of that all-important warmth and weight underpinning the live experience - omnidirectional mics of course. Personally, I would prefer some aircon rumble and a really solid, warm bass to a rolled-off anaemic bass free from rumble. The falling out of favour of omnidirectional mics with their very extended deep bass response (due to the increasing ambient noise in our modern world) has to some extent denuded modern recordings of the bass weight you hear in the hall.

                If I take the Gulda clip 4, (to hand) and I dramatically roll-off all the bass below 1kHz, (50Hz is -50dB) the 'air' I talk of in the reverberation tail of the piano notes as they fade into the room acoustic is unchanged. Here:

                Loading the player ...
                Clip 8: Gulda without/with severe bass cut - the reverberation 'air' is unchanged in the upper middle/presence band. It still sounds like the piano is in an acoustic space and can 'breath'.

                Another example (my own recording) where the inner tonal brightness works beautifully with the hall acoustic - polypropylene cones just do not have the resolution to reproduce this correctly:

                Loading the player ...
                Clip 9:Fairfield Halls

                Specifically, if we take one phrase from that recording, after the performer lifts his fingers off the keyboard, the note 'hovers' for about one second; there is, and there should not be, any change in tonality - the brightness, lightness and 'air' around the hovering notes should remain crisp until the next note is struck. Polypropylene speaker cones have a tendency to dry out this sustain sound, to over-damp those notes so that they are suppresses before the next note is played leaving little dry gaps between notes. This is what you should listen for when judging piano on loudspeakers*.

                Loading the player ...
                Clip 10: one phrase from my Fairfield Halls recording. The sustain tonality should be absolutely constant right up to the next note

                *Caution! An old marketing trick: many so called hi-fi speakers have this over-dry presentation and some makers recognise that even though journalists don't seem to. Since no one has access to Harbeth's RADIAL™ cone material, in a side by side with a RADIAL™ equipped Harbeth, a competing designer may feel compelled to elevate the tweeter level of his speaker to boost the upper harmonics giving the illusion of greater inner clarity. Many big-name brand UK speakers reviewed in HiFi News over the last years have frequency response plots which show that the tweeter has been deliberately set at multiple decibels - true - above a neutral, correct setting. They get rave reviews. This may play well in a short demonstration but it is the fast track to chronic listening fatigue and is not faithful to the recording or the live experience.
                Alan A. Shaw
                Designer, owner
                Harbeth Audio UK

                Comment


                • #9
                  Thank you Alan for the Gulda demo with and without bass cut. I hear the effect well. (I made no confusion between metaphorical and literal air!)

                  But I seem to be on the right lines suggesting that bass extension is essential to capture hall ambience, which, as you say is a separate issue. And am I right that the realism can only be heard if the bass is maintained in stereo - a mono sub will just not do it?

                  Two effects then - capturing the lower bass as it interacts with the recording space, and capturing the detail of the natural decay of the sound of instruments at higher frequencies.

                  You observe the RADIAL material does rather better than other cone materials with the latter effect. How much bass extension is required for the former effect. The SHL5 will clearly achieve more in the area that the P3.

                  Comment


                  • #10
                    Thanks!

                    That Fairfield Halls recording is extremely good. Thank you.

                    Comment


                    • #11
                      Originally posted by Labarum View Post
                      Thank you Alan for the Gulda demo with and without bass cut. I hear the effect well. But I seem to be on the right lines suggesting that bass extension is essential to capture hall ambience, which, as you say is a separate issue. And am I right that the realism can only be heard if the bass is maintained in stereo - a mono sub will just not do it?

                      Two effects then - capturing the lower bass as it interacts with the recording space, and capturing the detail of the natural decay of the sound of instruments at higher frequencies.

                      You observe the RADIAL material does rather better than other cone materials with the latter effect. How much bass extension is required for the former effect. The SHL5 will clearly achieve more in the area that the P3.
                      Very astute observations. Let's take them individually:

                      1) Dolby Labs invested much research effort into the reproduction of LF at home as a precursor to defining how many channels would be needed in a movie digital delivery system (DVD) for home use. They proved, and I'm sure they were right, that below about 120Hz, bass is sufficiently omnidirectional that it doesn't matter at all where in the room the bass radiates from: in front, behind, above, below, to the side - anywhere will do, or possibly even from the next room. Because of this omnidirectionality at low frequencies, there is no technical advantage to having two subwoofers as all LF soundwaves merge together. Furthermore, that omnidirectionality of LF at the recording means that bass, from whichever instrument, will be picked up almost equally by each and every microphone right across the orchestra, losing in the mixdown any sense of directionality or stereophony.

                      All LP records have had to be mastered and cut with mono'd bass and nobody believes that there is stereophonic information at LF on vinyl do they? There can't be if 20 mins playing time per side is needed. No consumer would accept 10 minutes just to have stereo bass. The issue here is the same as the one Dolby investigated: there is no point using precious bandwidth, playing time or data to encode LF information that contributes nothing at all to the listening experience. That's first class engineering thinking.

                      2) Yes, there are these two different but, in my opinion, defining components to a fabulous recording: warmth in the lower registers and simultaneously, the airiness and openness in the upper regions.

                      3) How much bass extension: no, the P3ESR does a really convincing job of replaying that weight and warmth despite its tiny size. That can only be because it's not the deep, deep bass that defines warmth and underpinning weight, it's the bass capabilities an octave or two higher - say, not 30 or 40Hz that's all important but 100-120Hz. The LS3/5a (like the P3ESR) has no real deep bass (physics can't be defeated) but it does have a very carefully contoured bass output where it really matters. The proof, just like the Gulda recording, would be to take a recording we agree has the sort of underpinning weight that sounds attractive, trim off the really deep bass below, say, 70Hz and see if what's left still sounds lush. I bet it would.

                      More on the late Gulda, here and here.
                      Alan A. Shaw
                      Designer, owner
                      Harbeth Audio UK

                      Comment


                      • #12
                        Thread fork point ...

                        Originally posted by Labarum
                        Can we discuss this more? Dolby defends the received wisdom, but I do know an audio-pro who is adamant that two subs are essential in some circumstances. If a recording is made of acoustic instruments using a simple microphone arrangement, some audio-pros would seem to say there is directional information into the deeper bass that can be relayed by two subs or a pair of full range speakers. If, however, a more complex microphone arrangement is used, or a "stereo image" is contrived in a mixing desk there is nothing to be gained from stereo subs. And of course, if you are playing LPs the data is not there no matter how the recording was made.
                        This thread has been split. To read more about stereo and subwoofers go here.

                        Discussion of the Harbeth RADIAL™ cone continues in this thread.
                        Alan A. Shaw
                        Designer, owner
                        Harbeth Audio UK

                        Comment


                        • #13
                          Three cones

                          I recently auditioned three British makes of speakers. One had a doped paper cone, the other had a doped linen cone and the third had an aluminium cone. What advantages does RADIAL have over those cone materials?

                          {Moderator's comment: we have covered that here before in detail. See main web site, item 10 this page: http://www.harbeth.co.uk/uk/index.ph...ignersnotebook

                          You need to go listen really.}

                          Thank you for the link. Unfortunately, I can't listen to a Harbeth without buying one first. I was interested in whether the three speaker cone materials that I mentioned exhibit particular sonic characteristics that are identifiable and can be attributed to the inherent nature of those materials. For example, I read that Alan Shaw does not like Kevlar cones and I'd like to know what it is about them that he finds disagreeable. He refers to other types of speakers sounding "dry", which he obviously regards as undesirable. Presumably Harbeths do not sound dry and I also presume that this is largely due to the RADIAL material used in Harbeth's speaker cones. If RADIAL speaker cones exhibit this inherent sonic quality, then it should follow that other speaker cone materials such as the three types that I've referred to would also.

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