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Hmmmm. How Does A Speaker Reproduce Many Frequencies At Once?

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  • #1

    Hmmmm. How Does A Speaker Reproduce Many Frequencies At Once?

    It just struck me that I don't think I understand how this is done. It's easy to envision how a speaker vibrates at one frequency, but how do they reproduce a wide band of frequencies (fundamentals and harmonics) at the same time?

    GeeDeeEmm
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  • #2
    This provides some insight: note the aspects of radiation area
    "Not a Speaker Designer - Not even on the Internet"
    “Pride is your greatest enemy, humility is your greatest friend.”
    "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

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    • #3
      Amazing isn't it? I think that's part of the intrigue of speakers. You feed it this jibberish AC signal ,,(as seen on an o-scope) and out comes this wonderful sound from a cone bouncing around...
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      • #4
        Originally posted by Sydney View Post
        This provides some insight: note the aspects of radiation area

        I think the most revealing portion of that page (thank you!) is the section titled Shrinking Radiation Area, which illustrates what we all know - that the higher frequencies are radiated from the center of the cone. (A number of other tidbits from the same chart regarding cone stiffness vs. cancellation, etc.)

        With that in mind, how is it possible, especially with a very rigid cone, for the cone to simultaneously vibrate at different frequencies across its area? I know that Altec once offered a model called the DiaCone, which was a small cone attached to the larger cone by a rather stiff "surround" of its own. How well these performed, I don't know, but the design is obviously based on the above. Note how they used an aluminum dust cover to further pronounce the high frequencies.

        But, I'm still back to the original question: how can a single cone simultaneously reproduce multiple frequencies? For instance, how can a voice coil vibrate at 500Hz and 6000Hz at the same instant?

        GeeDeeEmm

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        • #5
          Originally posted by 6thplanet View Post
          Amazing isn't it? I think that's part of the intrigue of speakers. You feed it this jibberish AC signal ,,(as seen on an o-scope) and out comes this wonderful sound from a cone bouncing around...
          Yes, it is amazing. Even if I could understand it, it is a wonderful thing.

          GeeDeeEmm

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          • #6
            Originally posted by gdmoore28 View Post
            ...With that in mind, how is it possible, especially with a very rigid cone, for the cone to simultaneously vibrate at different frequencies across its area?...
            Couldn't find a visual, but it is superposition of motion.

            Elements of Physics By M. Wellner page 284 - 286
            "Not a Speaker Designer - Not even on the Internet"
            “Pride is your greatest enemy, humility is your greatest friend.”
            "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

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            • #7
              Originally posted by gdmoore28 View Post
              how can a voice coil vibrate at 500Hz and 6000Hz at the same instant?
              Strictly speaking it doesn't. What causes it to vibrate is a complex waveform, which is a compilation of different frequencies. While 500Hz and 6000Hz may be contained within that waveform it's not as separate entities, but as components of an entity. It's not a unique situation, your eardrums do the same thing.

              www.billfitzmaurice.com
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              • #8
                http://physics.doane.edu/hpp/Resourc...Chapter_15.pdf
                "Not a Speaker Designer - Not even on the Internet"
                “Pride is your greatest enemy, humility is your greatest friend.”
                "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

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                • #9
                  There will be an aha moment,,,
                  Think instead of vibration - a surface being pushed and pulled at rates that matches the summed frequencies involved in the complex signal. The piston is being moved at varying rates.
                  A precision air pump
                  "Not a Speaker Designer - Not even on the Internet"
                  “Pride is your greatest enemy, humility is your greatest friend.”
                  "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."
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                  • #10
                    Sydney has provided a good illustration. Looking in the other direction, every complex waveform can be broken down into a sum of individual sines that make up the waveform. In school we proved this by creating a square wave in excel by simply applying the math adding the sine waves together for each harmonic of the square wave. The more harmonics added together (think higher frequency content), the more square the wave became.
                    "I just use off the shelf textbook filters designed for a resistor of 8 ohms with
                    exactly a Fc 3K for both drivers, anybody can do it." -Xmax

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                    • #11
                      A more complex example:


                      "Not a Speaker Designer - Not even on the Internet"
                      “Pride is your greatest enemy, humility is your greatest friend.”
                      "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

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                      • #12
                        Originally posted by billfitzmaurice View Post
                        It's not a unique situation, your eardrums do the same thing.
                        That's the amazing thing for me, that our brains can identify and situate all these components, i.e. it's not cacophony unless it's the intended to be cacophony.

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                        • #13
                          I don't know. I put my ear to the screen and did not hear any of those waves... ;)

                          Love the illustration of the complex waveform. Thank you as always Sydney. Its a great thing to remember that we work in sinewaves and listen to complex waveforms. Toole said it best: Not everything meaningful is measurable and not everything measurable is meaningful!
                          .

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                          • #14
                            Originally posted by mzisserson View Post
                            ... Its a great thing to remember that we work in sinewaves and listen to complex waveforms....
                            With that in mind - something to listen to:
                            https://meettechniek.info/additional...synthesis.html

                            "Not a Speaker Designer - Not even on the Internet"
                            “Pride is your greatest enemy, humility is your greatest friend.”
                            "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."
                            • 1 like

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                            • #15
                              Originally posted by Sydney View Post
                              With that in mind - something to listen to:
                              https://meettechniek.info/additional...synthesis.html
                              Bookmarked. Thanks! That is just awesome!
                              .

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