Different Bores

[Steve Inman]

The inside diameter of the 2nd valve tuning slide is the typical place manufacturers measure to determine the bore of their instrument(s). Willson seems to measure the OUTSIDE diameter, which leads to an inflated claimed bore.

It may be that a larger bore instrument is more open and free-blowing than a smaller bore instrument -- but other factors greatly influence this as well. What is the bore of your mouthpiece? What is the bore and taper of the leadpipe? Is the instrument a rotary or piston valve horn? Etc.

For sake of discussion, I'd suggest that a tuba with a claimed bore of less than 0.687" (unless it's a Willson) would probably be considered to be a small bore horn. (Several tubas with "smaller-ish" bores use .687 or .689, such as the Conn 52/54/56J, the King 2341, etc. So anything smaller than this is probably a small bore horn, and many folks would consider these specific examples to also be small bore tubas.) I would also suggest that anything between 0.728" to 0.770" would be considered "typical" bore dimensions. Finally, anything over 0.800" is likely to be considered a large-bore tuba.

Try a few (if you can) to see how horns of different bore play, using the same mouthpiece. Try different mouthpieces (with respect to "backbore") to see if that also affects the amount of air you need to use, vs. the playing characteristics of the horn(s) you're trying.

HTH,

[DonShirer]

I suppose that the numbers that have been quoted about bore size all refer to contrabass instruments. It seems logical to assume that smaller bass tubas and euphoniums would have smaller bores, but not necessarily in proportion to their length. For example my Eb tuba has a 2d valve ID of 11/16 (.86) in and a baritone has a bore of 9/16 (.56) in, both of which I always thought were typical of their size. Whereas if bore decreased proportionately a "normal bore" baritone would have an ID of about .43 inches, and I don't think I've seen any this small.

[tubacdk]

Having played a smaller bored 3/4 size tuba for at least 14 years, I can tell you it's been my experience that the smaller bore is capable of handling only a certain degree of volume before "Splatt" occures. It's very easy to overblow. Naturally, if you go to a larger bore, overblowing is harder to do, but it can still be done if you try hard enough.

I think generally that's true, but I've actually owned two tubas that have demonstrated otherwise. My RM-43 has a bore of .730" and can really handle a lot of push before getting splatty. .730" isn't that small, but compare that to my old 188 which had a bore of .770" and I could edge on the 188 quite easily. Then the HB-6 I owned had a bore of .810". That was a big tuba all around, and I would often get frustrated because the sound would edge out before I wanted it to, especially around low C.

I don't mean to be contrary, but I thought it should be mentioned that not all horns with small bores edge out, and not all of them with big bores don't.

-ck

[Rick Denney]

I suppose that the numbers that have been quoted about bore size all refer to contrabass instruments. It seems logical to assume that smaller bass tubas and euphoniums would have smaller bores, but not necessarily in proportion to their length. For example my Eb tuba has a 2d valve ID of 11/16 (.86) in and a baritone has a bore of 9/16 (.56) in, both of which I always thought were typical of their size. Whereas if bore decreased proportionately a "normal bore" baritone would have an ID of about .43 inches, and I don't think I've seen any this small.

Fred Young tells us that scaling an instrument requires maintaining the same dimensionless ratios, such as the ratio of bore diameter to length and bore diameter to bell diameter. Using this logic, he suggests that all tubas are very small in bore. A bore scaled from, say, a fleugelhorn would be about two inches in diameter. Of course, it would unplayable by humans. Thus, I would not go too far in trying to scale bore between different types of instruments. Few tubas have the same bore-to-bell ratio as most euphoniums, for example, and if they did you'd need six lungs to play them.

Not all smaller tubas have smaller bores. The Cerveny Piggy, for example, is often called a 3/4 tuba, but it has a bore of .830. Despite it's large bore, it still cannot make the massive sound of a much larger tuba, even though the larger tuba has a smaller bore.

Nor do I think all small tubas start to splat when played too loudly. I can play my 3/4 Yamaha 621 F tuba with as much air as I'm capable without making it splat, but there is a definite limit to its loudness and projection. The only way to make it louder is to use a shallow mouthpiece and go trombone-like, but even then there will be no splat if I do what I'm supposed to do.

In the process of buying a tuba, I would not consider bore at all. I would choose the tuba with the sound and playing characteristics that I want, and then take the bore it comes with.

Rick "who measures bore as a curiosity, not as a decision point" Denney