SteveM wrote: ↑Mon Jan 23, 2023 5:11 pm
Could someone explain how a counterweight could add resistance or change the way the air moves in the instrument? I mean, come on, it's outside of the trombone. I must be missing something.
I apologize in advance for the rant/lecture, but I’ve been thinking and reading about this for a long time…
This is a good question, and I believe that the answers we are given are well-meaning but slightly inaccurate. I’m going to split some hairs here, but I believe it’s important to understand how things work to understand how to change them.
Changes to the outside of an instrument
do not change the air flow
inside an instrument. From the player’s perspective, we don’t have to be concerned about air flow
inside a horn. What we are concerned with is the vibration and resonance of the standing column of air (I know, confusing) inside the horn.
We have to be concerned with air flow inside our bodies. We do our best to breath air in with minimal obstruction, and then blow air out with only as much tension as needed to produce a constant stream appropriate for the dynamic, range, and articulation. Once the air hits the lips and produces a vibration, we are mostly concerned about vibrating the air column.
Yes, some air is pushed through a horn, and some people spend a lot of time learning to push massive amounts of air in order to get a particular type of sound (usually called “big,” or “loud,” or “projecting,” or something like that). But that is simply the result of an imperfectly-sealed and irregularly-shaped vibrating surface—the lips. But it’s important to distinguish between (a) air that we use to excite the standing air column with the instrument and (b) air that we breath in and out.
lmalewic wrote: ↑Sun Jan 22, 2023 11:37 am
Anything that changes the way the air will movie through the instruments will change what we hear come out.
JohnL wrote: ↑Mon Jan 23, 2023 6:03 pm
It's an acoustic effect, but we perceive it as a change in resistance to air flow.
These, I believe, are half right. Again, it’s not the air flow, but the vibration and resonance of the air column. Anything added to or removed from an instrument affects the vibration of the air column.
Ever wonder why custom and boutique makers offer bells with different gauges (thickness of the metal)? Because it affects the way the air column vibrates, and changes the subjective “feel” of the horn to the player. Ever wondered why a regular weight brass slide feels different than a lightweight brass slide? It’s because the sleeves at the top of the slide tubes have been removed, affecting the vibration and resonance of the air column. Ever wonder why some bells have a soldered bead (e.g., Bach) and others do not (vintage Conns)? It affects the standing air column, and changes the subjective “feel” of the horn to the player.
So, adding a counterweight (or a slide bumper, or a detachable valve, etc.) to an instrument does at least two things. It acts as a counter-balance, and makes the horn feel less front-heavy. This makes it easier to hold the instrument becausethere’s less torque on the hands and wrist. It has an added affect of allowing you to sit and stand straighter: you don’t hunch over as much, you can get a fuller breath, and there’s less tension.
The other thing a counterweight does is act like a “stiffener. ” By adding a piece of metal to one particular place on an instrument (in this case, a brace in the bell section), you change the behaviour of the standing air wave within the instrument. That is, you change the way the nodes and the antinodes of the harmonic series excite the standing pressure wave inside the instrument.
A similar thing happens when you have a waterkey cork that is split or missing, or the tuning slide doesn’t fit quite right, or a valve is misaligned. The nodes and antinodes of the air column have been changed, which affects the feeling of the instrument (which we mistakenly call “air flow resistance”), and it affects the sound that comes out of the bell.
***
A lot of what I wrote above doesn’t matter to the player, but like I said, it’s important to understand what’s really going on.
You can prove it to yourself quite easily by playing a piece of music with the counterweight, removing it, then playing that same piece again. Just notice what happens. Most people notice that it feels different. Some people really like it one way, some another. Not good or bad, just different. Whether you like it one way or another is up to you. It’s subjective.
Rant over.