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  • High mass cabinets

    Do high mass cabinets made of materials like concrete, actually cause more resonance on bass than low mass ones?

    What's the physics of this?

  • #2
    Re: High mass cabinets

    Originally posted by speakerdesign View Post
    Do high mass cabinets made of materials like concrete, actually cause more resonance on bass than low mass ones?

    What's the physics of this?
    Resonance occurs where the force due to stiffness and the "force" due to mass for simple harmonic motion are of equal magnitude but of opposite sign and so cancel. A high mass relative to the stiffness will therefore result in resonances starting at low frequencies and a low mass relative to the stiffness will result in resonances starting at high frequencies. Since there are an infinite number of resonances in both cases more is not the right word. What matters is the number of resonances at audible frequencies, how loud they are relative to audibility thresholds and how quickly they decay.

    So for a subwoofer cabinet for example you probably don't want to use concrete since it is easy enough to construct a relatively light but stiff cabinet that places the first resonance well above the passband of the driver. This would not be easy for a midwoofer or midrange enclosure and so one might think about double walled concrete with sand in between if that way inclined.

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    • #3
      Re: High mass cabinets

      RE Physics:
      Young's Opposite Modulus*
      http://user.faktiskt.se/kraniet/Opos...e%20moduli.pdf

      * See Speed of Sound in:
      http://www.jiscdigitalmedia.ac.uk/gu...iples-of-sound
      "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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      • #4
        Re: High mass cabinets

        Originally posted by andy19191 View Post
        Resonance occurs where the force due to stiffness and the "force" due to mass for simple harmonic motion are of equal magnitude but of opposite sign and so cancel. A high mass relative to the stiffness will therefore result in resonances starting at low frequencies and a low mass relative to the stiffness will result in resonances starting at high frequencies. Since there are an infinite number of resonances in both cases more is not the right word. What matters is the number of resonances at audible frequencies, how loud they are relative to audibility thresholds and how quickly they decay.

        So for a subwoofer cabinet for example you probably don't want to use concrete since it is easy enough to construct a relatively light but stiff cabinet that places the first resonance well above the passband of the driver. This would not be easy for a midwoofer or midrange enclosure and so one might think about double walled concrete with sand in between if that way inclined.
        i have often heard that using a very high mass stand for a bookshelf speaker sounds like it gives you more bass depth. How can this be? wouldnt it be lowering the resonance since you are adding more mass?

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        • #5
          Re: High mass cabinets

          Originally posted by speakerdesign View Post
          i have often heard that using a very high mass stand for a bookshelf speaker sounds like it gives you more bass depth. How can this be? wouldnt it be lowering the resonance since you are adding more mass?
          How can a heavy or light speaker stand change the mass, stiffness or damping of a speaker enclosure? I think one would need to know what bass depth meant and the context of what was being compared with what in order to make a reasonable attempt at an answer.

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          • #6
            Re: High mass cabinets

            Originally posted by speakerdesign View Post
            i have often heard that using a very high mass stand for a bookshelf speaker sounds like it gives you more bass depth. How can this be? wouldnt it be lowering the resonance since you are adding more mass?
            You seem to be parroting a lot of weird audiophool myths, between this comment and the "woofer speed" nonsense.
            --
            "Based on my library and laboratory research, I have concluded, as have others, that the best measures of speaker quality are frequency response and dispersion pattern. I have not found any credible research showing that most of the differences we hear among loudspeakers cannot be explained by examining these two variables." -Alvin Foster, 22 BAS Speaker 2 (May, 1999)

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            • #7
              Re: High mass cabinets

              Originally posted by andy19191 View Post
              How can a heavy or light speaker stand change the mass, stiffness or damping of a speaker enclosure? .
              because if you tightly fix the stand to the speaker, it becomes part of the cabinet. So now mass increases. If its not tightly fixed, then this isnt true.

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              • #8
                Re: High mass cabinets

                Originally posted by speakerdesign View Post
                because if you tightly fix the stand to the speaker, it becomes part of the cabinet. So now mass increases. If its not tightly fixed, then this isnt true.
                That statement is another instance of parroting weird audiophool myths.
                www.billfitzmaurice.com
                www.billfitzmaurice.info/forum

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                • #9
                  Re: High mass cabinets

                  Originally posted by billfitzmaurice View Post
                  That statement is another instance of parroting weird audiophool myths.
                  In the current issue of Absolute Sound a reader wrote in to correct one of these myths, and he was correct in his letter. However, the reviewer replied by taking him to task (in not so nice of a way, I might add) and perpetuating the misinformation. It's a shame because for most readers his comment will be seen as coming from a place of informed understanding and authority on the subject and some of these people will never be able to see it correctly because they will use the magazine as a higher source of knowledge.
                  Click here for Jeff Bagby's Loudspeaker Design Software

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                  • #10
                    Re: High mass cabinets

                    Originally posted by Jeff B. View Post
                    ... taking him to task (in not so nice of a way, I might add) and perpetuating the misinformation. It's a shame because for most readers his comment will be seen as coming from a place of informed understanding and authority on the subject and some of these people will never be able to see it correctly because they will use the magazine as a higher source of knowledge.
                    Unfortunately the same could be said of websperts who often forget their humble backgrounds and chose condescension
                    "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."

                    Comment


                    • #11
                      Re: High mass cabinets

                      Originally posted by speakerdesign View Post
                      i have often heard that using a very high mass stand for a bookshelf speaker sounds like it gives you more bass depth. How can this be? wouldnt it be lowering the resonance since you are adding more mass?
                      You're simply removing vibration so you can hear the bass rather than the buzz and rattle that is usually considered bass in most people's systems.

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                      • #12
                        Re: High mass cabinets

                        1) "Do high mass cabinets made of materials like concrete, actually cause more resonance on bass than low mass ones?"

                        2) "i have often heard that using a very high mass stand for a bookshelf speaker sounds like it gives you more bass depth. How can this be? wouldnt it be lowering the resonance since you are adding more mass?" With the reply
                        "because if you tightly fix the stand to the speaker, it becomes part of the cabinet. So now mass increases. If its not tightly fixed, then this isnt true."

                        Speakdesign, 1) this pertains to movement and resonances of the individual enclosure walls.
                        2) this pertains to movement of the enclosure as a whole body.

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                        • #13
                          Re: High mass cabinets

                          Originally posted by speakerdesign View Post
                          Do high mass cabinets made of materials like concrete, actually cause more resonance on bass than low mass ones?

                          What's the physics of this?

                          One desires to minimize the influence of resonances, which are related to natural frequencies.
                          The fundamental components of mechanical vibrations are stiffness, mass, and damping.
                          The most fundamental equation for natural resonance frequency is:

                          Natural Frequency = 1/(2x Pi) x SQRT (Stiffness/Mass)

                          So
                          Natural Frequency is a functional of SQRT (Stiffness/Mass).

                          So one has to consider how both the stiffness and mass are changed when altering a baffle.
                          IF stiffness and mass are increased equally, then the natural frequency stays constant.
                          To double the natural frequency, holding mass constant, the stiffness must increase 4 times.
                          When adding material to a wall, the stiffness of the wall is impacted by the stiffeners shape and its placement on the panel.
                          The damping force is not considered to impact natural frequency, as it only a very slight change. If additional damping material is added, the additional mass is added to the system mass, so the natural frequency could decrease.

                          When walls are built of concrete, the mass is high, so increases in stiffness are important. The damping forces required to control the resonance need to be increased.

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                          • #14
                            Re: High mass cabinets

                            Never occured to me that a suitable material might not be heavy /dense. How about those OTT magico cabinets ..?

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                            • #15
                              Re: High mass cabinets

                              Originally posted by bill poster View Post
                              Never occured to me that a suitable material might not be heavy /dense. How about those OTT magico cabinets ..?
                              Magico cabinets are definitely stiff and well damped.


                              http://magico.net/Technology/Enclosu...losures_02.php
                              On the above link, moving the cursor into the pop-up panel will bring up supplemental text.

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