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

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  • #31
    Originally posted by View Post
    Turntable Thoughts by Paul Messenger

    Even the simplest music is likely to contain enormous numbers of these frequencies at all these different levels at any one time, and the problem for the record deck (and the hi-fi system as a whole) is to get as much of this back as possible, while avoiding adding too much extra of its own.
    In other words (or the words of our founding fathers): "The Sound, The Whole Sound, and Nothing But the Sound."

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    • #32
      Originally posted by View Post

      ​So, who do I complain to, to get all those bumps in the road fixed? LOL
      The railroad crossover Department can smooth out those rough tracks ;-)

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      • #33
        I've had this same question in my head for a long time, although I kind of know the academic answer, it's still hard to get my brain wrapped around it at times.

        I try to envision the concept starting at the source of the music. We've all played with bass sine tone generators on the computer to watch our sub-woofers go 'Flappa-flappa' after we put the drivers in the box... a sine wave being the most simple form of tone that can be generated.

        Play a sine tone at 80 Hz. and you have a pure tone with no harmonics... but harmonics are the 'clues' that tell us what instrument we're hearing... what's making the sounds we're hearing. Is it a bass guitar, the human voice, or a tuba?

        All those 'extra' little squiggles on a frequency response graph are what give us the information we need to tell the difference between the pure sine tone underneath the tone we hear, and the actual instrument we're listening to. Like every person's voice is different and discernible, each instrument has it's own 'signature' of harmonics added to the pure tone of whatever base frequency is being produced.

        Since our voice, for example, can reproduce the underlying tone with all of the extra harmonics, then it stands to reason (in my mind) that since one device (my voice) can produce many frequencies at once, and a microphone can pick up those many frequencies and turn them into electrical impulses... that a speaker must be able to reproduce those many frequencies to lesser or greater degrees of success as well.

        On second thought... scratch all that... it IS magic. I guess that's why it's so hard to get really accurate reproduction of music with speakers... in some cases we're trying to reproduce original tones with an instrument (speaker driver) that is dramatically different in shape or size that what originally made the tone in the first place. It's really amazing that with all the elements in the sound reproduction chain that we can get music to sound as good as it does.

        TomZ
        *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
        *Part 2 *Gluing multiple curved laminations of HDF *Cello's Speaker Project Page

        *Building the "Micro-B 2.1 Plate Amplifier -- Part 1 * Part 2 * Part 3 * Part 4 * * Part 5 'Review' * -- Assembly Instructions PDF

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        • #34
          Tom, and anyone else interested in the topic of sound reproduction, I recommend a book "Sound Reproduction: The Acoustics and Psychoacoustics of Loudspeakers and Rooms" by Floyd Toole. It's a hefty read, to be honest I haven't read all of it, but a lot of information in there presented in a manner that you don't need to have an engineering degree to understand.

          In the first few chapters there is a nice explanation of the difference in sound reproduction between a speaker and an instrument in the room, making a lot of good points of why it is extraordinarily difficult to exactly reproduce any acoustic instrument.
          Don't waste your money on a new set of speakers, you get more mileage from a cheap pair of sneakers. Next phase, new wave, dance craze, anyways it's still rock and roll to me!

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          • #35
            Measurement and Visualization of Loudspeaker Cone Vibration ( Wolfgang Klippel and Joachim Schlechter ) is an insightful work on modern analysis.
            "Not a Speaker Designer - Not even on the Internet"
            "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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            • #36
              Originally posted by tomzarbo View Post
              I've had this same question in my head for a long time, although I kind of know the academic answer, it's still hard to get my brain wrapped around it at times.

              I try to envision the concept starting at the source of the music. We've all played with bass sine tone generators on the computer to watch our sub-woofers go 'Flappa-flappa' after we put the drivers in the box... a sine wave being the most simple form of tone that can be generated.

              Play a sine tone at 80 Hz. and you have a pure tone with no harmonics... but harmonics are the 'clues' that tell us what instrument we're hearing... what's making the sounds we're hearing. Is it a bass guitar, the human voice, or a tuba?

              All those 'extra' little squiggles on a frequency response graph are what give us the information we need to tell the difference between the pure sine tone underneath the tone we hear, and the actual instrument we're listening to. Like every person's voice is different and discernible, each instrument has it's own 'signature' of harmonics added to the pure tone of whatever base frequency is being produced.

              Since our voice, for example, can reproduce the underlying tone with all of the extra harmonics, then it stands to reason (in my mind) that since one device (my voice) can produce many frequencies at once, and a microphone can pick up those many frequencies and turn them into electrical impulses... that a speaker must be able to reproduce those many frequencies to lesser or greater degrees of success as well.

              On second thought... scratch all that... it IS magic. I guess that's why it's so hard to get really accurate reproduction of music with speakers... in some cases we're trying to reproduce original tones with an instrument (speaker driver) that is dramatically different in shape or size that what originally made the tone in the first place. It's really amazing that with all the elements in the sound reproduction chain that we can get music to sound as good as it does.

              TomZ
              ​No need to over think it, it works so leave it at that. How did your loudspeakers do at the MWAF?

              Comment


              • #37
                Originally posted by View Post
                Turntable Thoughts by Paul Messenger


                The prime function of the turntable system is to mechanically interface the disc and cartridge so that the cartridge is able to extract the maximum amount of musical information from the disc. To start with, we must understand that the “audio bandwidth” is the range of frequencies the human ear can hear, and extends in frequencies from 20 to 20,000 cycles per second. Likewise the human ear can easily detect differences in loudness that encompass 60dB, or a ratio of 1,000,000:1. Even the simplest music is likely to contain enormous numbers of these frequencies at all these different levels at any one time, and the problem for the record deck (and the hi-fi system as a whole) is to get as much of this back as possible, while avoiding adding too much extra of its own.
                To understand the dimensions involved in the record system we shall construct an enlarged model in which one micron (one thousandth of a millimeter) is represented by one inch. A midband modulation in the groove at a “typical” level (1kHz, 5cm/sec) gives a 16 inch peak-to-peak excursion for the stylus, while a 50Hz organ pedal at 10dB higher will require 10’ 6" and the low level harmonic of a violin (10kHz, -40dB) only 0.068"! A typical stylus with a “line contact” profile on a high quality cartridge would produce vertical oval “foot-prints” on the groove walls 10" by 4” and would deform the vinyl by about one inch (twenty times the size of the violin harmonic). The stylus itself is about 30' high, and is attached to a bent pipe that represents the cantilever of 50' diameter and 275' length, extending from a 2000’ long cartridge body that is some 80’ from the record surface! The arm has a diameter of 450’ and crosses 1300’ above the record surface from its pivot point nearly 4 miles away! This approach deals only with dimension, not mass or velocity, yet it certainly illustrates the problems of relative magnitude that the turntable system has to deal with. In fact it is quite amazing that record decks work as well as they do, and it is hardly surprising that there are differences among them.

                Now that really puts it in perspective!

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