crowmadic

I'm in the dark about understanding what "round" as opposed to "square" tuning slides do. Can someone fully explain the difference in sound and playing experience?

The BuZZ

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rowuk

I have asked this question also many times and all of the technical reasons that I have heard sound a bit lame (or just wrong), so I have invented my own myth:
IF both slides have the same wall thickness, have the same bore size, are made out of the exact same alloy AND are annealed or tempered the same (assuming no braces or braces at exactly the same location) then they will SOUND the same.
The reason that I say this is that when we blow into the horn, it is not our breath molecules that are bouncing off of the back wall a couple of milliseconds later. Our breath molecules bump into the ones in the horn and they keep bumping until a wave is set up between our diaphragm and the back wall - like ripples in a pond. Those standing waves determine the sound, intonation, efficiency and "perceived" projection.
The actual "aerodynamics" of the horn are only designed to use our air up in a set amount of time, allowing us to breath at intervals that keep our body supplied with oxygen (this is why I don't like extremely "free blowing" trumpets). These aerodynamics are not the primary "sound changing" factors.
I think the reason that various slides sound different is that:
1) two bends versus one gradual bend sets up a different resonance pattern in the slide (because they are not annealed or tempered the same)
2) the square slide is made out of thinner brass
3) many times the square slide has a brace, whereas the rounded ones don't
4) different materials are used
I think that the difference in construction not so much the shape is responsible.
Any sharp bends in the tubing (like in a square slide) will change the perceived air resistance (actually impedance as Tootsall has explained several times), most likely due to minor disturbances in the airflow.

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NYTC

WOW,
Well done,Rowuk.!!!!!!!

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Dave Mickley

I want to add one more thing to rowuk's explination, I used to teach Hydraulics and every joint and curve adds resistance and that is called Delta P. By making your tuning slide a reversed slide you are removing one lip of tubing to flow over. these little lips or joints are small but when you take a lot of lips/joints they add up. that is one very good reason to get your valves aligned properly. Just some more to think about and discuss. Dave

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If I remember my Benade correctly, the instrument maker must deal with acoustics and fluid dynamics at the same time. (Hmmm, "Fluid Dynamics might be a great name for a trumpet ensemble!)

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Pedal C

I think "fluid dynamics" come into play at the bar after the gig!

If you had the same horn and two slides (one of each shape) and made as identically as possible, I wonder if a difference in sound could be caused by changes the player would make (subconciously) to the chops to compensate for the difference in the "free-blowingness." I don't like excessively wide open horns either because I feel like the embouchure has to do something different that I'm used to, so maybe that causes as much change and the different acoustic environment. Or maybe not...it's really late...

Jason.

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rowuk

Even the free-blowingness has to be kept in pespective.
What we perceive as free-blowing is more than how fast our air disappears. If the horn "speaks" easily, we are in a good room and we can hear ourselves - the horn will be judged as "free-blowing". Take that same horn into a small stuffy room or outdoors near a big lake and it seems to be a lot stiffer-regardless of how fast your air disappears. That is why a test in a music store tells you NOTHING about the horn. Marching band on a cold day gives you exactly the same experience - your air disappears and it still feels like you are blowing into a brick wall!
I think all other factors being the same, the environment will be a MUCH bigger influence than the VERY minor difference in resistance between the 2 slides.

A reverse leadpipe is completely different than the other ones that we have discussed here. It allows for the longest leadpipe (still incorporating a tuning slide) BUT forces us to move the leadpipe/bell brace much further back. On the Bach instruments that I have played, the reversed leadpipe models have played more "openly" but have not had that core sound or projection that I consider to be THE Bach trademarks. In those cases, I consider the trade off not to be to my liking. The tuning bell modded Bachs seem to play best with a sound post attached where the standard Bach bracing was.

At the end of the day, our physical/mental condition and the playing qualities of the room are REAL and affect our playing in a much greater way than any tuning slide. We are creatures of habit - so pick one and stick with it. The more we fool around, the more we create uncertainty during critical times in our playing life.
If I was buying a new horn (actually I am!), my preference would be a round or ovate slide, well-braced and without the reversed leadpipe.

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