Mass = HOOEY?

Discussion in 'Trumpet Discussion' started by Blind Bruce, Aug 21, 2009.

  1. Sofus

    Sofus Forte User

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    I have a question that I´ve
    wanted to pose for a long time now:

    When we talk of the effects of MASS,
    isn´t it actually the effect of STIFFNESS
    that we´re after?

    Mass is added to stop walls from vibrating.
    This is done by making the walls thicker, but
    isn´t it the increase in stiffness that we want,
    and isn´t the extra mass just something that
    comes along?
     
  2. stumac

    stumac Fortissimo User

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    Stiffness, what I have in the joints these days, comes with advancing age.

    50 years since I did Applied Mechanics, forgot it all after passing exam, not relevent to my work, you are probably right.

    Regards, Stuart.
     
  3. NickD

    NickD Forte User

    I have changed up my discussion about mass in a wind column since I wrote that article. At the time, it seemed pretty cool, and I stand by SOME of it. There is a different twist that I got from Dr. Tom Moore, the science editor of the ITG journal.

    We had a conversation one time about an experiment he was doing energizing trumpet with artificial lips (a bit different from the old salpingometer methods of Cardwell and Benade). Now, I forget the details of what they were looking for but they were doing FFT's of the sound produced. That is to say, they were looking at the harmonic content of the tone. For some reason, after a couple of tests, they decided they needed to stabilize the horn better, so they laid a sand bag across it to prevent it from vibrating as much. Low and behold, they detected a measureable difference in the FFT produced.

    Now, in his lectures, Dr. Moore discusses very thoroughly the idea that a trumpet is NOT a percussion instrument and that any sound leaving the vibrating bell is so minimal in comparison to the sound coming out of the wind column as to make it immeasureable (excess of -90 db down). He did have a theory as to why damping out the bell vibrations would make the difference they detected.

    His theory was that the vibrations were feeding back into the lips mechanically through the mouthpiece! While the sound from the shaking bell was negligable, the feedback to the lips can help keep energy in the system just like the reflections in the wind column. This supports the idea that adding some mass to the system MIGHT have an impact. The more mass the mouthpiece hass, the harder it is to shake it, so the higher frequencies don't get back to the lips. However, lower frequencies could get through. There is the possiblity of a slight filtering effect. This means a heavy horn and mouthpiece ought to play a bit darker. A lightweight horn and mouthpiece ought to play a bit brighter. This part is a different conclusion from what I had reached in the online article I wrote came to.

    Now, as a disclaimer, Dr. Moore has never specifically done experiments to verify this. His remarks were made to me in a discussion after a physics conference at which he spoke on brasswind acoustics(I was the conference chairman and he was the inivited speaker - I invited him).

    In any case, these effects are probably quite sublte and given the number of other variables involved, not the least of which is the adding of a human to the system, and well, things get extremely complicated and it is probably impossible to truly say yes or no it does or doesn't work.

    Perhaps Dr. Moore will do some specific experiments to settle the hash once and for all!

    Or not!

    Nick
     
  4. Sofus

    Sofus Forte User

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    Very interresting, Nick!

    Maybe two sorts of feedback back to the lips
    could be present:

    *the walls vibrating, resulting in AXIAL vibrations
    of the metal along the trumpet, finally reaching
    the mouthpiece and lips

    * the walls vibrating, making the whole trumpet
    vibrate in your hand.

    In the second case the actual weight of the trumpet
    ought to matter, not only the wall stiffness.
    Maybe the actual weight of the trumpet would matter
    also in the first case, or would only the stiffness decide
    everything in this case?

    Please give your opinion on this, Nick!
     
    Last edited: Aug 22, 2009
  5. NickD

    NickD Forte User

    Sofus,

    I have to get to an early meeting, so this will have to be short.

    You raise a very interesting thought. That sounds very reasonable that some added wind column feedback could even occur.

    The stiffness and mass both enter into the equation that would adjust the Q of the horn. For example, the added term that shows up when a damping factor is applied to a simple harmonic oscillator is b/2m, where b is the damping coefficient and m is the mass. So changing m, even if b doesn't change will change the resonant frequency of a SHO, and also it's Q.

    As Rowuk implies in his post, this is extremely subtle and complex stuff and there are MANY factors involved in making a good horn. I would never say that a heavy horn is better. Nor would I say a light horn is better! The shape of the wind column, the coupling of the mouthpiece and the shape of the mouthpiece are probably the biggest things involved in what makes a horn system good, but it also depends on how the whole thing works with the PERSON playing it.

    So, I am not prepared to say that mass makes NO difference; only subtle.

    Ok, I really have to run. I'll check back later!

    Peace, all!

    Nick

    PS: Hey, Sofus! We're both approaching our first 1000 posts! Yay! ;-)
     
  6. rowuk

    rowuk Moderator Staff Member

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    We cannot rule out anything. In the case of the Monette trumpets, the "heavy" bells are annealed (soft) versus the tempered bells that others use. When we talk about adding mass to a resonant systems, several things CAN happen:
    Lower resonant frequency: this COULD make the horn sound "darker"
    Higher resonant frequency: by making the resonant object "stiffer"
    Higher inner damping: this can change the feedback to the player, it can also change the effects of the resonating cavity by reducing the effects of a less stable mechanical construction. It could also increase "projection".
    Lower inner damping: unbraced mass will vibrate MUCH longer than lighter objects

    Depending on the designer, we may desire the mass to be less stiff or more stiff, depending on what we are trying to achieve.

    Example: we want more projection without loss of feedback to the player. We increase the mass of the bell, but move the bell brace further back towards the valve cluster.

    Please do not forget that resonance does not just cause ADDITION to the signal, it can also cause cancellation of useful or detrimental frequencies.

    For some very interesting info check this link out. The research paper is in German only, but the pictures also tell a very clear story:

    http://iwk.mdw.ac.at/Forschung/pdf_...nn_Schallbecherschwingungen-von-Trompeten.pdf

    This only talks about bells and resonance. Simply add a new brace and we have a complete new story, make the BRACE heavier and we start over.

    Mass is not as simple as many pimpers like to think. Mass is not necessarly there to damp vibration. It can move it to a different frequency. One thing is clear, mass in motion tends to stay that way, so before adding it, we need to be sure what we are exciting. Judging from other "mass" threads here, the only thing I am sure that was predictably excites were the brain cells that cover "illusions".

    Many years ago it was commonly accepted that loudspeaker cabinets made out of stone or brick were less resonant than anything else and thus were "better". B&W did some research and proved differently. The results of their work lead to the development of their "matrix" series. Essentially a honeycomb structure was acoustically more inert and the lighter weight stored and passed less energy. The myth was busted. The same applies to trumpet. Mass is only useful when strategically and intelligently implemented. It gives designers a set of parameters to use to create, or recreate more choices.

    Anyone familiar with Dave Monettes' work know that building heavy trumpets gave him insite into making better lighter trumpets. My present Prana3 is everything that my much heavier Ajna2 was and more. The new Prana Ajna is yet another step more "radical". The next generation of horns will also benefit from this experience.
     
  7. Sofus

    Sofus Forte User

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    Jul 26, 2008
    So what you´re saying is:

    * Mass can be altered when MASS is the parameter
    that changes your horn in the desired direction

    *Stiffness can be altered when STIFFNESS is the
    parameter that changes your horn in the desired direction


    Have I got that right, rowuk?
     
  8. Mark Bradley

    Mark Bradley Pianissimo User

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    I don't understand this post. First you seem to imply anyone that dare use heavier type gear (mouthpiece, valve caps, even heavier trumpets themselves, etc.) deserve nothing but derisive laughter and disdain-- "such people" must be nothing but complete morons you seem to say; but then you go on to invalidate your entire premise by pointing out the obvious huge difference it would make if brass instruments were heavy-- using the non sequitur of replacing brass with steel.

    Heavy valve caps, heavy weight mouthpieces, more mass in mouthpieces, heavy weight trumpets, the material used etc. make an undeniable difference in an instrument-- how it plays, how it sounds. Now whether specific variables are a virtue or not is certainly open to debate and probably ultimately up to the likes and dislikes of each individual musician-- but nothing that warrants finger pointing and derision like getting a good belly laugh at the expense of the awkward gait of the village idiot.
     
  9. Blind Bruce

    Blind Bruce Pianissimo User

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    Mark, my original post was prompted by some mass adding devices that I ran across while perusing an on line catalog. They seemed rather dubious in their intended purpose so I added the laugh icons. If anything, I alone am the moron to which you refer. I meant no disrespect to anyone.
    After reading the various responses, I feel that if you have a well designed horn, it is probably better to leave well enough alone and leave the mass situation up to the designers.
     
  10. Sofus

    Sofus Forte User

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    .

    That´s also one of my conclusions. Horn design seems far too
    complex for anyone except a specialist to know what he or she
    is doing. Altering one single thing will most likely change the horn
    in several ways, not possible to easily predict, so at least changes
    that can´t be undone should be avoided. Swiching caps and such
    IS a reversable process, so one can try that without danger . . .
     
    Last edited: Aug 22, 2009

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