Out-of-tune tubas

[Art Hovey]

Several folks above made remarks to the effect that the woodwind instruments are way ahead of us in terms of intonation, and I suspect that may be correct. Funny thing is, it's the woodwind players who seem to have the most intonation problems in the several different groups that I play with. Is it because they are unable to adjust their pitch, or is it because, like piano players, they never learn how?
Surely the good Lord distributed tin ears evenly through every section of the band, yet it's in the woodwind section where they are always most apparent!

Getting back to the original question: the "standing sound wave" in a brass instrument has "pressure antinodes" at several locations in the instrument, and that set of locations is different for each note. If the region near one of those antinodes is altered slightly by a dent or a manufacturing irregularity it makes very little difference. But if several of them are altered in similar fashion the combined effect becomes significant for that particular note even if the individual irregularities are nearly invisible.

[iiipopes]

Art, I respectfully disagree about one point: if the antinode is in just the right place, a dent or misplaced brace can really alter the intonation and perceived "stuffiness" of a particular note. For example, on my Besson, there is an antinode on mid line D right in the middle of my valve block. Some time ago I had a dent taken out of the knuckle between the first and second valves that had occluded that particular port about 50%, and my mid line D went from perfectly in tune to 20 cents flat. I actually took the round end of a ball peen hammer, and gently tapped on that knuckle, ever so slightly putting a bit of the dent back into the knuckle until I got my intonation back. It did not, and has not, affected the intonation of any other note on the tuba.

Disclaimer: I discourage anyone else to try this at home. I was lucky to be able to experience a singular event in that I was able to see a direct effect on one particular note from one particular action at one specific place without having to consider multiple variables. Moreover, I have less than $750 invested in this tuba, including original purchase price, shipping, a couple of mandatory repairs, mouthpiece, and a few elective repairs. So if I had screwed it up, there is no significant loss. It would be just one more aspect of "personality," along with the holes in the rim from the tuba being improperly stored on its bell sometime along its 35 years before it got to me.

[MaryAnn]

Well,my choice as I see it is, a great blending,appropriate size tuba with a nebulous low register,or a great sounding tuba with great intonation in all ranges but just too big.I guess the Thor wins for now.Quintet horn size is somewhat up for debate.Low A with a 40c wide slot is pretty much agreed upon as not good...I may take both and see how it goes.

Methinks you'd be out some of your bank account just from trying a Norwegian Star. Perfect quintet horn, just dandy all-round. I'd get the Star Light if I felt like throwing the $$ around.

MA

[sloan]

Good reading: The Physics of Musical Instruments by Fletcher and Rossing.

Rick "noting that this has been discussed in the past but without a clue as to how to search for it" Denney

Bingo on the reference. I'm out of town - can you please post the page number of the "figure that explains it all"? You know the one I mean... I love seeing the light bulb go off above people's heads when they first see that figure.

Better yet - can you please scan it and post a picture. Then we'd always have something to point at.

[Rick Denney]

Good reading: The Physics of Musical Instruments by Fletcher and Rossing.

Rick "noting that this has been discussed in the past but without a clue as to how to search for it" Denney

Bingo on the reference. I'm out of town - can you please post the page number of the "figure that explains it all"? You know the one I mean... I love seeing the light bulb go off above people's heads when they first see that figure.

Better yet - can you please scan it and post a picture. Then we'd always have something to point at.

Okay, here it is. From Page 217 of the book referenced above.

It shows that the pitches of the impedance peaks vary with respect to each other quite significantly with the ratio of straight to conical tubing in a compound horn. In English: The relative tuning of partials vary with each other a lot on the basis of the ratio of straight and conical tubing.

Rick "who happened to have the fax here at the office--the book is at home" Denney

[sloan]

And now...just for giggles...note that the "ratio of cylindrical to conical tubing" changes every time you mash a button...

[Rick Denney]

I've even heard of a manufacturer that made a bottom bow for a 6/4 BBb too narrow and too short...

Rather than starting over on the bow, they "V"-ed it out to line up with the bell and upper bow. Of course, the instrument played a bit sharp. Pitches that were normally flat on that particular model "seemed" in tune, but other pitches were horribly sharp...

You're being a nasty bastard, heh, heh.

Rick "who manages" Denney

[iiipopes]

At the last community band concert, warmup went well so we had a few extra minutes before actually starting the concert. I was able to lay my 1971 186 along side my colleague's newer 17 3/4 inch bell 186. The overall length of the horn is the same, but my bottom bow is tighter, and my overall wrap is tighter, necessitating the lengthened tuning slide to accomodate the retrofit upright bell that Dan Schultz did a superlative job for me.

His horn has a more "vanilla" tonality, and the usual trend of slightly flat 5th partials. Mine is right on for 2nd space C first valve, possibly slightly sharp for 12 B nat, alright for 2nd valve Db, and only needs the alternate fingering of 12 for midline D, and not always then, if we're somewhere in proximity to a 1st inversion Bb major chord.

But with the change in the overall balance between cylindrical and conical tubing, effectively delaying the start of the conical bugle, and then with the shorter St Pete bell being as wide or wider in the throat, so there is more expansion in less linear space, even if only a few inches, I can tell you that just like a flugel, my low range can go sharp if I'm not careful, and the top 1/2 octave of the bass clef can go flat if I'm not focused.

The tradeoff is more even overtones and a broader sound, which projects better, sounds "rounder" in all registers, and starts glimpsing east towards Alex territory.

I'm with bloke that the lower bow must have more to do with overall tone and intonation than most people would like to consider.

[kingconn]

The thing is that all of the horn has alot to do with it. Although when you play the second partial the antinode falls somewhere 2/3 through the horn so generally problems in the lower partials tend to be in the last 2/3 of the horn. If you move your hand around when you play a long tone you can feel antinodes, any enlargment in the bore in these places will lower those pitches. You can lower the same pitch if you shrink the bore or the expansion of the bore at the node. The problem is when an adjustment is made and the node or antinode for another partial falls along the same area. Again ,only bore changes will affect intonation. Brace placement will only affect the response.
mike

[MaryAnn]

I just knew that picture was going to show up sometime in this thread!

MA