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{Updated Oct. 2017}
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The role of the loudspeaker

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  • #16
    That looks good to me too as an observation. See, this really isn't dificult.

    OK, now a bit of a leap of imagination.

    Taking the above observations, and looking at the photo of the workings of a quality microphone here, and thinking about the process of sensing sound at the microphones and then pumping sound into the room via the loudspeakers, what do we observe?

    Clue. Look at the photo of the microphone diaphragm in the above link, then look at the masthead photo of a range of loudspeakers here .....

    There are quite a few alternative observations (that is, with only our eyes, not brain) that can be made of the comparison between the mic and the speaker. How many can you make?
    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

    Comment


    • #17
      In a sense the microphone is a reverse image of a speaker box, a deflationary device as opposed to the inflationary nature of the loudspeaker. Both the loudspeaker and the microphone are trying to capture and reproduce the same event as vividly and realistically as possible with the simultaneous aim of being as unobtrusive as possible.

      That is, the limitation of the microphone does not want to be detected in the playback by the speaker and the speaker does not want its limitations to impugn the integrity of the performance of the microphone.

      They want to be identical twins as opposed to siblings of the same family despite differences in size, weight, sensitivity, impedance, distance (one being a witness to the actual event, the other removed in time and space).

      Comment


      • #18
        Originally posted by allthumbs View Post
        In a sense the microphone is a reverse image of a speaker box, a deflationary device as opposed to the inflationary nature of the loudspeaker. ...
        That's true in as much as the microphone senses pressure and the speaker generates pressure, but describe what you see when you look at the pictures of the microphone and the loudspeakers. As simple and basic observations as my granddaughter might make. It was her first day at 'big school' last week ....

        Click image for larger version  Name:	first day school.JPG Views:	1 Size:	522.8 KB ID:	74304

        The deductions can wait 'till later. Let's just observe for now using the language that a nearly five year old would. It will be worth it!
        Alan A. Shaw
        Designer, owner
        Harbeth Audio UK

        Comment


        • #19
          There is a corresponding vibrational (mechanical) relationship in play between the mic’s diaphragm and the speaker cone. The two employ the same electronic means to translate voltage impulses into movements (just guessing). The surface areas of the two layers differ in shape as the each is optimised to fulfil its own purpose: the mic diaphragm needs to register the incoming sound waves (hence a membrane) while the speaker cone needs to disperse them, i.e. ‘return’ them back to the listening environment, omnidirectionally. In doing so the speaker effectively recreates the changes in ambient air pressure that the mic registered.

          Comment


          • #20
            Speakers adapt basic concepts of the human ear that represents human listening.
            • Two ears, two speakers. Sounds like a plan.
            • Membranes in speakers send acoustic waves to the ear.
            • Speaker membranes (as well as microphone membranes) follow the concept of the eardrum (tympanic membrane).
            • Using stereo positioning, the listener and the speakers all share the same face angle for optimum listening.


            There is more than just two ears and two speakers.
            • Room acoustics also need to be considered in addition to stereo positioning. In most cases, rooms and room objects can influence sound reflection in a negative way so that even the best speakers can sound terrible. Speaker stands, absorbers, diffusers, bass traps and other accessories can help to improve the listening experience but would also impact typical interior design of living places.
            • Multi-directional (poly-directional, dipole, bipole) speaker concepts try to produce specific sound reflections and diffuse sound with still one or two speakers to workaround limitations of typical stereo speakers and stereo positioning. While these concepts can show positive results in some rooms it can also cause the opposite. Room acoustics still play a major role.
            • Surround sound introduces more speakers (e.g. 5.1 and 7.1) to produce more effect-full and space filling "3D sound" and "sound everywhere".
            • Typical 5.1 and 7.1 surround concepts didn't really overcome fixed seating positions for the listener. New surround sound concepts such as Dolby Atmos can have the benefit of using many small speakers that are almost invisible and can better adapt to individual room acoustics and listener positions. However, proper individual and personal setups that match specific room acoustics would be very complex and costly, especially if such systems are also meant to play standard stereo music. Therefore, sticking to simple stereo positioning with a good pair of speakers is still be achievable for most of us and in most rooms.

            Comment


            • #21
              Originally posted by S Magus View Post
              There is a corresponding vibrational (mechanical) relationship in play between the mic’s diaphragm and the speaker cone. The two employ the same electronic means to translate voltage impulses into movements (just guessing). The surface areas of the two layers differ in shape as the each is optimised to fulfil its own purpose: the mic diaphragm needs to register the incoming sound waves (hence a membrane) while the speaker cone needs to disperse them, i.e. ‘return’ them back to the listening environment, omnidirectionally. In doing so the speaker effectively recreates the changes in ambient air pressure that the mic registered.
              Maybe, but is that an observation? No, it's a deductive statement.

              I'm struggling to make the point that I just want to see observations. I'm beginning to think that we have lost the ability to merely observe. Can I please refer you to my quote from Prof. Faraday's diary of a century and a half ago, a piece of purely observational reporting:

              Click image for larger version  Name:	image_4017.jpg Views:	1 Size:	140.1 KB ID:	74312
              1685*. Again, placed a piece of soft iron opposite the pole of a bar magnet a foot long, an inch broad and 0·4 thick (the figure is to a scale of about one half ); and then placing paper over the bar and magnet, sprinkled fine filings on and observed the lines depicted. It was beautiful to see how they flowed into the iron at the end near the magnet and how they flowed out again at the further part from a comparatively much larger surface— and also to see the concavity of the lines outside the iron near the equatorial part of it, shewing the double curvature— and the beautiful character of the streams of force into the air or space from the further part.
              No more statements please, as they will be Moderated out. If you can write with the clarity of Prof. Faraday, we can incrementally build-up to a memorable concept that will carry the entire audience with us.
              Alan A. Shaw
              Designer, owner
              Harbeth Audio UK

              Comment


              • #22
                Originally posted by mactrix View Post
                Speakers adapt basic concepts of the human ear that represents human listening.
                • Two ears, two speakers. Sounds like a plan.
                • Membranes in speakers send acoustic waves to the ear.
                • Speaker membranes (as well as microphone membranes) follow the concept of the eardrum (tympanic membrane).
                • Using stereo positioning, the listener and the speakers all share the same face angle for optimum listening.

                There is more than just two ears and two speakers.
                • Room acoustics also need to be considered in addition to stereo positioning. In most cases, rooms and room objects can influence sound reflection in a negative way so that even the best speakers can sound terrible. Speaker stands, absorbers, diffusers, bass traps and other accessories can help to improve the listening experience but would also impact typical interior design of living places.
                • Multi-directional (poly-directional, dipole, bipole) speaker concepts try to produce specific sound reflections and diffuse sound with still one or two speakers to workaround limitations of typical stereo speakers and stereo positioning. While these concepts can show positive results in some rooms it can also cause the opposite. Room acoustics still play a major role.
                • Surround sound introduces more speakers (e.g. 5.1 and 7.1) to produce more effect-full and space filling "3D sound" and "sound everywhere".
                • Typical 5.1 and 7.1 surround concepts didn't really overcome fixed seating positions for the listener. New surround sound concepts such as Dolby Atmos can have the benefit of using many small speakers that are almost invisible and can better adapt to individual room acoustics and listener positions. However, proper individual and personal setups that match specific room acoustics would be very complex and costly, especially if such systems are also meant to play standard stereo music. Therefore, sticking to simple stereo positioning with a good pair of speakers is still be achievable for most of us and in most rooms.
                This is a deductive statement, not an observation, as requested, and too complex for this stage in the game. It is full of very advanced concepts (even I need to really think about what's written, and this is my own specialisation!) that will need to be explained in considerable foundations-up detail. See the problem of over compexity here with treatment solutions.

                Remember: we're aiming to write with the simplicity and clarity of a nearly five year old. Nothing more. That was the genius of Michael Faraday. Brilliant observation and accurate note taking. It was Maxwell, years later, who added the deduction and maths bit based on Faraday's completely reliable and perfectly documented observations.

                Great science starts with careful observations and proper documentation.
                Alan A. Shaw
                Designer, owner
                Harbeth Audio UK

                Comment


                • #23
                  The electronics and again I am guessing are acting as a cross over. So the electronics are much larger than the microphone membrane which is the opposite relationship of the crossover in a loudspeaker.

                  The number of screws holding the pressure sensing diaphragm are as numerous as the number of screws in the speaker baffle despite the lightness of the materials used in the microphone.

                  There is only one diaphragm in the microphone recording all of the same information that can only be reproduced with a minimum of at least two diaphragms in the speaker boxes.

                  Comment


                  • #24
                    Originally posted by allthumbs View Post
                    ... There is only one diaphragm in the microphone recording all of the same [sound pressure] information that can only be reproduced with a minimum of at least two diaphragms in the speaker boxes.
                    Bingo.

                    Let's really deeply think about that observation. Let's try to construct in our mind the recording venue with its microphone(s) and the home replay room. When we've make them tangible constructs in our mind, we can fill them will sound waves, which we can also visualise, and walk around those virtual rooms noting the position of the pressure sensor(s) and the pressure pumps. The entire edifice of audio reproduction is built on these foundations. Serious consideration of this matter will pay handsom dividends later; that cannot be over-emphasised.

                    There is one device to sense the pressure in the recording environment (the microphone, which senses the pressure only at the microphone, not anywhere else in the studio) and there are multiple sound pressure pumps (loudspeaker drive units) modulating the air pressure in the listening room from the place that the speaker drive units are positioned in the listening room.

                    What do we think about that as a concept? Does it sound like a winning formulae for 'high fidelity sound'?

                    I suppose we should define 'high fidelity sound' as meaning that the air pressure patterns in the studio as they pass the microphone bear great fidelity to the air pressure patterns generated by the speakers in the replay room.

                    Objectively, is that air pressure 'high fidelity' likely to be found even under the most optimistic conditions with a $1,000,000 audiophile system? Suppose that we could actually see sound waves in motion, would we observe the same patterns - that is, pattern fidelity - between those found in the studio and the home?
                    Alan A. Shaw
                    Designer, owner
                    Harbeth Audio UK

                    Comment


                    • #25
                      I don't want to steer Alan's project off course. I am totally sympathetic to the aim of focussing on mere observation--it's what the great philosopher Ludwig Wittgenstein was constantly getting us to try to do: just look and see (the problems of philosophy, he maintained, lay in trying to stop us from seeing what we want to see or expect to see)--but it is striking that Prof. Faraday uses the word "beautiful" twice in the observation Alan quotes.

                      Is that significant? (Treat my post as an observation about Prof. Faraday's observation.)

                      Comment


                      • #26
                        Originally posted by David Schalkwyk View Post
                        I don't want to steer Alan's project off course. I am totally sympathetic to the aim of focussing on mere observation--it's what the great philosopher Ludwig Wittgenstein was constantly getting us to try to do: just look and see (the problems of philosophy, he maintained, lay in trying to stop us from seeing what we want to see or expect to see)--but it is striking that Prof. Faraday uses the word "beautiful" twice in the observation Alan quotes.

                        Is that significant? (Treat my post as an observation about Prof. Faraday's observation.)
                        Yes, it is. It related, doubltess to the matter we discussed here. Prof. Faraday believed that he was observing the hand of god at work in his various experiments.
                        Alan A. Shaw
                        Designer, owner
                        Harbeth Audio UK

                        Comment


                        • #27
                          Originally posted by David Schalkwyk View Post
                          I don't want to steer Alan's project off course. I am totally sympathetic to the aim of focussing on mere observation--it's what the great philosopher Ludwig Wittgenstein was constantly getting us to try to do: just look and see (the problems of philosophy, he maintained, lay in trying to stop us from seeing what we want to see or expect to see)--but it is striking that Prof. Faraday uses the word "beautiful" twice in the observation Alan quotes.

                          Is that significant? (Treat my post as an observation about Prof. Faraday's observation.)
                          'Beautiful' at least does not assign any assumptions, only the observers appreciation (a butchers counter could be beautiful to one observer and yet horrify a second).
                          Getting to know my C7ES3

                          Comment


                          • #28
                            Originally posted by A.S. View Post
                            I suppose we should define 'high fidelity sound' as meaning that the air pressure patterns in the studio as they pass the microphone bear great fidelity to the air pressure patterns generated by the speakers in the replay room.
                            But there is not only recorded studio sound. What about live performance in concert halls without recording equipment? In such scenarios, sound from instruments and voice go directly to listeners without technical equipment.

                            Originally posted by A.S. View Post
                            Objectively, is that air pressure 'high fidelity' likely to be found even under the most optimistic conditions with a $1,000,000 audiophile system? Suppose that we could actually see sound waves in motion, would we observe the same patterns - that is, pattern fidelity - between those found in the studio and the home?
                            Not the same. That seems almost impossible. We try to reproduce the original as close as possible.

                            Comment


                            • #29
                              We are concerned here solely with the recording and later, reproduction process. We have not even considered - and perhaps we do not need to consider if our analysis of the recording studio is robust and universal - alternative scenarios, such as the live sound experience at the concert hall.

                              I agree with you. The sound pressure patterns (waves) in the recording studio must be fundamentally different to those sound pressure patterns in the home reproduction environment. Can we list the reasons why they are so very different?

                              My starter ....
                              1. The surface area of the woofer cone that generates the pressure pump effect in the listening room is about 250 times bigger than the surface area of the sensing diaphragm of the microphone ....


                              Consider this vital point:
                              • The microphone has made a precision measurement of the sound pressure modulation in a tiny matchbox-size volume of air around its capsule diaphragm. It cannot sense the air pressure anywhere in the studio other than where it is placed. That means, it cannot sense precisely the sound pressure waves 1cm or 10cm or 1m away from where it is placed.
                              • The microphone is a precision sampling device, but only sampling at the exact point in the studio where it is mounted. Nowhere else.
                              • The loudspeaker, in comparison, on replay, has a (woofer) surface area very much bigger than that of the microphone capsules. In fact, about 250 times greater.
                              • That means that the speaker's pressure generating surface area - the woofer - cannot make a precision air pressure displacement of the matchbox-volume that the microphone captured. In effect, the loudspeaker has smothered and averaged and degraded the microphone's sensing precision and blasted sound pressure out into the room from the point in the room where the speaker is located.
                              • To perfectly reproduce the sound waves sampled by the tiny microphone diaphragm, the speaker diaphragm would have to be no bigger than it. Clearly, the woofer is very much bigger. The tweeter diaphragm is approximately the same diameter (and hence surface area) as the microphone capsule .... but where is it in the listening room?

                              And we have not considered in any way the quality of sound reproduced by the speaker, nor its fancy technical specifications. We're just thinking about air pressure into the recording chain at the microphone, and out through the speakers.

                              Any other factors?

                              P.S. Keep in mind how many bits 256 states represents in a digital system .....
                              Alan A. Shaw
                              Designer, owner
                              Harbeth Audio UK

                              Comment


                              • #30
                                OK, I will have a stab at this. The microphone in the studio is inundated with competing signals from various signal sources that “compete” for the available air pressure in the studio to arrive at a very small but static solitary target at the same time in some semblance of balance providing a cohesive unified “wave”, like pouring a bucket of water into a funnel to fill a bottle.

                                To some degree the studio is a known quantity and the air pressure can be manipulated by various means to ensure the filling of that bottle can be filled in an orderly fashion, allowing for a pour, a trickle, a drop, no spillage and filtering out impurities.

                                The same wave, a finished product, arrives at the loudspeaker end then has to be picked apart and the bottle of sound has to be uncapped, and in a continual process decantered into at least two bottles with a spray nozzle attached to each in a process of instantaneous filling and emptying dispersed into a vast unknown.

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