Does a larger bore mean less resistance?

Discussion in 'Horns' started by PlatinumPiece, Dec 26, 2016.

  1. PlatinumPiece

    PlatinumPiece Pianissimo User

    Dec 23, 2016
    And do you know any trumpets that have a "low resistance"?
  2. OldSchoolEuph

    OldSchoolEuph Mezzo Forte User

    Apr 1, 2011
    Absolutely not. Resistance is a perception, and a bore size of say .468" is not all that different from a bore of .459" in terms of fluid capacity (especially since actual resistance to flow would be a function of friction at the wall, and that area is only a tiny bit greater or lesser relative to cross-sectional area and thus volumetric capacity). Resistance is a perception of the amount of energy needed to sustain, shift, or amplify the tone. It is an energy issue, specifically the energy that the mechanics of the horn sap from the pressure waves created by embouchure as they move toward the reflection point at the rim and exciting sound waves radiating outward. Along the way, energy is needed to move the material of the horn itself, and for the constructive and destructive interference that all acts to shape the final tone (through, geometry, mass placement, shortcuts like braces, damping effects of the alloy and structure, and freedom of the bell to resonate, which includes thickness among the factors affecting.) Most of the controlling factors are fairly constant horn to horn within basic weight class, but the big variable is resistance derived from turbulence. Standard construction introduces a turbulent point ahead of the first bend while reversed does not. Bach square style slides have turbulent tight bends while single radius slides produce far less disruption in the flow and fewer transitions between flow states. The valves are a turbulent zone and position relative to other zones can affect the number of transitions. The more turbulent length, and the more transitions, the more energy is lost as sound waves, which are compression waves propagating through a fluid, are disbersed by the lack of consistent fluid density and velocity.

    Now, lots of folks believe that resistance is how much air fits in the pipe. And lots of folks do not accept that the feeling of fighting to blow through the horn could be anything related to physics other than mere flow. So I came up with a demonstration tool to show how this works. Get 8-1/2 feet of 3/4" soft vinyl tubing at the hardware and a metal funnel to stick in the end. Tape your mouthpiece shank to fit snug, and you have a natural trumpet. The huge .750" bore can move far more volume than any trumpet. But when you play it, it feels like blowing into a brick. This is because of the massive damping effect of the tubing material sapping energy from the sound waves you produce. That is what we feel as resistance.

    So, low resistance horns GENERALLY will be lighter, reversed, single radius slides, harder brass (not copper), fewer braces and thinner in the bell. BUT, not always. There are so many factors, including how you and you mouthpiece interact with the horn, you ultimately have to try horns, keeping track of their attributes, looking for correlation between design features and what works for you. Then, the greater concentration of those elements you can find in a horn, the better the odds it will be right for you.
    Vulgano Brother likes this.
  3. trumpetsplus

    trumpetsplus Fortissimo User

    Jun 11, 2006
    South Salem, NY
    In terms of Bach trumpets, the difference between the L (0.462") and ML (0.459") is the thickness of the tubing. The thinner tubing of the L bore gives a larger inside diameter. By the way, both models share the same (size) valve block and the pistons are interchangeable. As OldSchoolEuph says, there is little difference in fluid flow.
  4. Vulgano Brother

    Vulgano Brother Moderator Staff Member

    Mar 23, 2006
    Parts Unknown
    So is it the thinner tubing that makes the large bore Bach C more desirable than medium large?
  5. VetPsychWars

    VetPsychWars Fortissimo User

    Nov 8, 2006
    Greenfield WI
    Sure, the Buescher Model 215 "Custom Built" and the Model 217 "Lightweight 400".

    But why? Once you match the piece to the horn, the resonance will make more easier play.

  6. trumpetsplus

    trumpetsplus Fortissimo User

    Jun 11, 2006
    South Salem, NY
    It makes it different. "More desirable" is in the eyes of the beholder.
  7. Sethoflagos

    Sethoflagos Utimate User

    Aug 7, 2013
    Lagos, Nigeria
    Piccolos have a smaller bore than tubas.

    This tells us (almost) everything we need know about the relationship between bore size, register and resistance. If we spare a moment to think about it. All other things being equal, for any given pitch, a larger bore generates more resistance simply because a larger volume of resonating air needs redirecting. It's difficult to despatch an incoming cricket ball with a ping pong bat.

    As a first order approximation, frictional and turbulence losses are irrelevant. Trumpets dance to an entirely different tune.
  8. rowuk

    rowuk Moderator Staff Member

    Jun 18, 2006
    Resistance has little if anything to do with airflow. It has even less to do with turbulance (our air is actually not even moving that fast).

    What one perceives to be resistance is based on how well we hear ourselves. This can be based on the room that we play in or the actual construction of the horn. Take whatever horn that you own and play it in a reasonably large bathroom - lots of feedback, the horn feels free blowing. Now take that same horn outdoors where there is a wide open space with no buildings. That very same horn feels stuffy. Horns with lighter bells and less bracing give the player more feedback and the impression that the horn has less feedback. Horns where we hear ourselves less make us play harder, that takes more air and energy. The artisans can build substantial feedback into a small bore horn by using a thin bell and mounting the brace close to the valve cluster. It will appear to be very free blowing. An artisan can take a large bore horn, use a thick bell and mount the braces forward, it will appear "stuffier".

    We can compare playing trumpet to electricity. Our sound, which consists of a standing wave in the horn is the AC component. Our air which only has to flow to keep the lips "firing" is the DC component.

    I would maintain that resistance would have to be measured indirectly: how long of a phrase can you play? A longer phrase means more resistance. A more efficient horn will have higher resistance (actually reactance).
  9. OldSchoolEuph

    OldSchoolEuph Mezzo Forte User

    Apr 1, 2011
    For me, it would be the reverse. My phrase length is controlled by needing to breath - usually to refresh, not refill, the lungs. The harder I work against perceived resistance, the sooner I need oxygen.

    Of course, so called free blowing horns also tend, not always, but often, to include elements that lead to looser centering, so in the balance that too could make one work harder and negate my point.

    Trumpets are very complex systems, and there are only correlations to be found for any of these characteristics, not absolutes.

    So to the OP: in the end, you have to try different horns and see what "fits" for you. We all have our own unique ways in which we interact with the instruments, and their attributes affect us differently as a result. The more you try out, the better you will know what you are looking for.
  10. Bflatman

    Bflatman Forte User

    Nov 27, 2008
    Manchester, England
    So some people think that the bore of an instrument that might be for example 0.45 inches or 0.48 inches is causing resistance to airflow when you blow through a tiny hole in a mouthpiece that is no more than 0.14 inches in diameter hmmmmmmmm

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