What causes a horn to have bad intonation?

[AndrewKennedyMusic]

Hi, I have recently checked a few different trumpets and found that some had poor intonation, mainly in the upper register, with an open fingering. For example, the worst trumpet I tested; with an open fingering C below the staff was in tune, C in the third space was in tune, but high C was more than 50 cents flat. This wasn’t the case with every trumpets so I know it’s not my playing.

My question is, given that the harmonic series should be predictable, especially with an open fingering, what inherent design flaws could cause a trumpet to be so flat in the upper register?

For what it’s worth, the trumpet with poor intonation had a few significant dents in the open tubing (not valve tubes). Could dents cause this? If so why?

The

[LittleRusty]

I spent some time with Mike Thompson tinkering with the gap on my trumpet using a sleeved Stomvi mouthpiece to attempt to adjust the way the harmonics laid on my instrument. My primary complaint was that the D above the staff was very difficult to hit accurately.

Basically with my existing gap the upper harmonics were compressed causing the slots to be lower than they should be.

There is a lot of physics underneath how the horn responds and how the slots lay. The natural harmonic series of an open pipe is not the same as what we expect today, especially when playing with a fixed pitch instrument like a piano.

Getting into areas where others are more qualified to discuss, the leadpipe and bell tapers are part of the solution too.

[shofarguy]

Charles Hargett, a friend whom I met at the Kanstul Musical Instrument Company nearly twenty years ago, (or possibly Jack Kanstul. I'm not sure) told a story of riding in a car with Byron Autrey (another brass instrument guru and friend of Zig Kanstul) who held a trumpet in his hand and pointed to a place along the bell and claimed that if he dented the bell just there, a certain specific note would not play properly. Then, if he removed the dent, that note would return.

As LittleRusty explained, the gap between the end of the mouthpiece and the beginning of the lead pipe - the mouthpiece gap - is crucial to the intonation of the horn, particularly how spread out the pitches of partials play. This phenomenon was made most apparent by Bob Reeves.

I have followed the advice of Flip Oakes (Wild Thing fame) and a few others and learned to "clock" each mouthpiece when inserting it into whatever horn I'm playing. I have found that there is one orientation that plays the best. Sound, response and intonation all come together best at one specific rotational point. I make note of that orientation and make sure my mouthpiece is always "clocked" properly. It makes my playing much more consistent and takes away a lot of extra, useless exertion.

On the "self" side of things, I have noticed that when I have taken some time off playing, my horns don't play in tune! Something happens to them. The truth is in two things, I believe. Each horn is a collection of compromises that require the player to conform and compensate in order to play in tune. We subconsciously use this learned set of adjustments when we play. Changing instruments exposes these adjustments, because they work against us if we bring them to a horn with really different design choices. We have to unlearn the compensations of the previous horn and learn the new ones. This is a conscious process, at first, so the differences stick out.

Those same design compromises affect the results of our embouchure approach and technique. In the past two or three days, there's been a thread where a TH member posted a video of himself playing four trumpets. One was his daily driver, one was brand new to him that day and the other two were recent additions to his playing. While these particular instruments have similar, or even familial characteristics, one can hear the different design choices and how they affected the OP while he played.

In other words, it isn't always the horn and it isn't always the player, but the goal is to find instruments that work together with the player to produce a good result. Sometimes, the player needs to adjust. Sometimes the horn isn't a good fit. Sometimes, the trash can might be the answer!
_________________
Brian A. Douglas

Flip Oakes Wild Thing Bb Trumpet in copper
Flip Oakes Wild Thing Flugelhorn in copper


There is one reason that I practice: to be ready at the downbeat when the final trumpet sounds.

[lipshurt]

Several different things….
First of all, regarding “clocking the mouthpiece”…if that makes a difference it’s because something is not perfectly concentric,either the rim of the mouthpiece is not the same contour all tne way around, or, less likely, the exit wall of the Shank is different thickness on one side.

For your basic octaves: in order of importance
1) lip intrusion. More lip intrusion means upper register will be sharp.

2) length of throat, exit wall thickness, backbore length and size. In other words backbore shape and total length. This is a lot of variables but all of them get wrapped up together. Long throat is flat up high, short throat is sharp up high, and it’s pretty drastic. Getting this right for your lip intrusion, and your trumpet, is very important for getting the octaves lined up.


3)gap, but it’s no where near as drastic as lip intrusion or throat length.

4) bad match of leadpipe tapers and bell tapers. Some pipes just don’t work with certain bells. You can’t always just mix and match.

For other issues not octaves

1) leaky valves. This is huge, and it can be just one little area on one valve that causes big problems, even if your “compression”seems fine. If there is a low spot on a valve that lets air leak across a place in a piston where there is very little contact with the cylinder wall, If there is nodal point right there, one or two notes on the horn could be drastically weird.either sharp or flat or bad centering. If you see a shiny area on a piston that’s a low spot.

2)valve alignment. Can help, but it’s not gonna fix anything drastic. Bad alignment affects tne feel of the horn more than the intonation of certain notes.

3) leaking Amado water keys. These things leak a lot more that people think they do.

4) bad match between leadpipe and bell.
_________________
Mouthpiece Maker
vintage Trumpet design enthusiast
www.meeuwsenmouthpieces.com
www.youtube.com/lipshurt