The Trumpets Are Closed?

Discussion in 'Trumpet Discussion' started by Bachstul, Aug 27, 2009.

  1. Sofus

    Sofus Forte User

    Jul 26, 2008
    Gee! You make me blush, Robin! Thanks!!:oops:

    I only have a couple of questions left now:

    1) If I put a rigid wall in front of the bell, I would
    say that the bell was Closed, since I see
    the wall as some "closed door". This is not the only
    way that one could reason about it. One could say
    that when there´s a rigid wall in front of the bell,
    the bell is in fact Open since it it "more open than the
    rigid wall". Which do you mean when you say that the bell
    is Open, and what would you say that the bell is if a
    rigid wall is in front of it, Robin?

    2) If you, like me, would call a bell with a rigid wall in front of it
    Closed, and since we know that a rigid wall is a heavier
    media than air which will place the wall impedance at the far right
    in the Smith chart, a conclusion must be that a bell is Closed when
    the air inside the trumpet meets a media with Higher impedance than
    Since the air inside a tube generally has Higher impedance, we have
    the opposite situation; the air inside the trumpet meets a media (the
    outside air) with a Lower impedance than itself. Since this is the
    opposite of the Closed situation, doesn´t this actually imply that the bell is Open?

    3) Normally when a "thinner" media with lower impedance meets a "thicker" media with higher impedance wave Pressure is High in that interface while wave Speed is Low. I would have thought that in the case of a trumpet the inner air has High impedance and the outer air has Low impedance. In this case the wave Pressure would be Low and the wave Speed would be High.
    Which is true as far as the trumpet is concerned?

    4) Are you saying that due to partials or other things, the air impedance
    inside the trumpet is Complex (in a mathematical sense),
    and that this is the thing that makes the bell Closed although
    some things (like the ones above) are pointing towards that it is not?
    It is true that the air pressure inside the trumpet is very high and that
    the air in there can show some Complex behaviour, but is this the physical
    explanation to why the bell is Closed instead of Open, as you see it?
    I´m not at all sure that you´re saying this, just asking!
    If, however, you´re not saying this, what then is it that makes my reasoning
    why the bell is Open not hold water?
    It is also true that in the extreeme high register the high notes will be
    projected out of the bell so efficiently that (almost) no energy is
    reflected back into the trumpet. The trumpet will act as a megaphone
    for these high notes, and the notes will simply be amplified versions
    of the mouthpiece buzzing. In this high register total matching between
    trumpet and outer air is at hand, I should think, so this could not be a
    case of Open bell. Instead it should be a case of Totally Matched bell.
    But, in the "normal" range, what is it that makes my reasoning
    why the bell is Open not hold water?

    I´m sure you can explain this, and my only goal here is really
    to understand the trumpet better!!

    Thanks for taking the time to help me!:-)
    Last edited: Sep 3, 2009
  2. Sofus

    Sofus Forte User

    Jul 26, 2008
    This topic is discussed in a sticky called


    and I have therefore continued the discussion there.

    It will be too much for everyone to keep writing the
    same things in both threads, I think, so

    Last edited: Sep 3, 2009
  3. Sofus

    Sofus Forte User

    Jul 26, 2008
    Suddenly I realize that since this is not my thread
    it therefore is not for me to move the discussion either!
    I should have asked you first, Bachstul, and I hope it´s OK
    although it´s a bit late to ask . . .:-(
  4. Bachstul

    Bachstul Mezzo Forte User

    Jan 25, 2009
    That's an "A-Okay", SOFUS. You brought forward great ideas, suggestions, and info.

    I've always been the kind of guy to initiate a new topic of conversation, then stand back and listen to everyone talk; I can learn more about the topic, and the person.

    I admit, I never browsed the sticky thread, "how does a trumpet work"......

    I hope you receive more positive reputation points for your work.
  5. Sofus

    Sofus Forte User

    Jul 26, 2008
    Thank you, my friend!

    Points of reputaions are always nice to get,
    and still; nothing feels greater than getting
    an increase in KNOWLEDGE.

    I know for a fact that you agree to this, since
    you yourself pose the kind of questions that you do!

    Let´s hope that rowuk has the tíme to help us all out
    in defining Open & Closed as well as explaining why the
    thoughts of mine that I´ve already revealed are wrong.
    After all, he´s one of those who have the knowledge to
    explain this, and so far he´s been more than generous in
    sharing his knowledge with us!
  6. rowuk

    rowuk Moderator Staff Member

    Jun 18, 2006
    If the wall is a short distance in front of the bell, it will increase the "length" and mouth size of the bell. The impedance will go up at lower frequencies. If we seal the bell off, we have no more trumpet. We have a beer bottle (well maybe lätt oel..).
    The air in the trumpet does not have a fixed pressure. It varies dramatically with frequency. If it did not have a higher impedance at those frequencies, no standing wave would be formed and thus no trumpet.
  7. trumpetnick

    trumpetnick Fortissimo User

    Nov 16, 2005
    Vidin, Bulgaria
    How understanding these stuff would change my playing? Or is this more of an intellectual debate and comparing your (intellectual) packages? :twisted:
  8. B15M

    B15M Forte User

    Dec 30, 2003
    Monroe Ct.
    I read this whole thing but not the thread "how a trumpet works"

    I apologies if I'm repeating something from the other thread.

    After reading I have decided that the air is only used to set up the wave.

    I keep reading on here about playing more efficiently. Some how this thread is tied to that.

    When I want to play louder, I put more air in the trumpet. What does this do to the wave?

    When I play lead with a big band, how do I play more efficiently? When I want more volume, don't I just use more air?

    How do you use more air efficiantly?
  9. Sofus

    Sofus Forte User

    Jul 26, 2008
    Thank you for you answer, Robin!

    I can´t help wondering if maybe we talk about different things.

    I´m beginning to suspect that you´re actually talking about the impedance
    at the interface between lips and mouthpiece, not trumpet and bell like I am.
    This is a graph describing the impedance at the interface between
    lips and mouthpiece:


    When I talk about Open or Closed bell, I actually refer to the
    reflection that happens at the interface between bell and outer air.
    Here´s a document to atscribe what what happens at the interface
    between any two medias:


    Actually, that´s not quite true. As you can see in Case C, also a lower
    impedance would give a reflected wave. All it takes is that the impedances
    at both sides of the interface are different. But then, the impedance inside
    the trumpet being lower than the outside impedance maybe isn´t very likely,
    and I suspect that this is what you mean.

    Yes, but:

    1) isn´t that the case where the bell should be called Closed?

    2) isn´t that the case when the wave pressure has its maximum and
    the wave speed its minimum at the interface between bell and rigid wall.
    Isn´t this actually Case B with the blue dot?

    Like I said in the beginning: maybe we talk about different things.
    Maybe when you call the bell Closed, your reference has to do
    with the impedance that the lips see, i.e. the impedance at the
    interface between lips and mouthpiece as seen from the lip side
    (Interface A in my document).
    Since there is a high wave pressure in this interface, the lips maybe
    see something "Closed". Even so, this still doesn´t have to mean that
    the bell is seing something "Closed" when seing the outer air.

    The way I´ve understood things, Open or Closed has to do with two things:

    1) Whether there´s a difference between the impedance at the rightmost side
    and the leftmost side of an interface (if not, no reflecting takes place)

    2) From what side of the interface you´re looking

    If you have some thoughts about this and also find the time to respond
    to this, despite all your gigs and such, I sure would appreciate it, Robin!


    Hey Nick!

    1) Yes Nick, this IS intellectual!
    Don´t interfere when it´s above your intellectual standard!:evil:

    2) This will NOT change your playing, Nick!
    The best thing you can do to sound better is to sell your horns!!:evil:


    Hey B15M!

    I would say that part of playing efficiently is to play in a way
    that your lips still close properly. They work as a sort of valve
    switching air on and off, but if you blow them apart or in other
    ways make them leak air in the phase when they should be shut,
    overtones will be weak and you will not be properly heard.

    The exercises where you play softly are among other things
    intended to give you a good, efficient embouchure where the
    lips really close off the air stream when they should, i.e. in the
    "close phase".

    When you blow harder wave speed and wave pressure goes up.
    This is not the same thing as the fact that more air also will
    pass the trumpet. Wave speed means that the air molecules inside
    the trumped act like pendulums, swinging forward-backward-forward-
    backward inside the trumpet at a certain speed. When they swing
    forward the will actually "crash into" some other molecules swinging
    backwards at that instant. This will cause the pressure buildup at the
    "place of impact" that we call Wave Pressure.
    The swinging (wave speed) and the "crashing" (wave pressure) happens
    of course equally often, and is very closely related to the frequency
    of the note that we play.

    Last edited: Sep 12, 2009
  10. trumpetnick

    trumpetnick Fortissimo User

    Nov 16, 2005
    Vidin, Bulgaria
    I know that you crave to lay hands on them, but there are more intelligent ways to ask...Besides, Spada is still selling new horns, you know...You can have my configuration if you want.

    SPADA MUSIC AG - Tonangebend im Trompetenbau
    Last edited: Sep 9, 2009

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