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Another recent question that came in had to do with bore of horns, as in what is actually meant when people say a horn is large bore?
Where this gets confusing from the start is that most horns are about the same bore. Most horns today are either .468 inch, 12 millimeter, or a size between the two, the metric tubing size being slightly bigger. Usually European horns are metric so in reality an Alexander 103 actually has a larger bore through the valve section than a Conn 8D.
What is usually meant when the term is thrown around by players has to do with the size of the throat of the bell. A large throated bell is most easily perceived as being large bore in the area where our hand would fit in the bell. Thus, in common usage in our horn world, a large bore horn would be one with a large throated bell and the 8D is much larger bore in this area of the horn than the Alexander.
My own primary double horn for many years was large bore and is a model I have always been curious why it has never caught on in the USA as it really is a great horn. The horn in the photo is my Paxman 25AND. The “A” is for the American bell throat which is their largest model, “N” for nickel silver, “D” for detachable bell. The 25 model designation is for a dual bore double horn where the tubing through the B-flat horn is normal, conventional bore size and the tubing through the F horn valve slides is noticeably larger, full half-inch tubing! The result is a horn that is free and easy blowing with a big, orchestral sound. What I have noticed is it seems to be a horn that if you are not used to how free it feels it does not seem to test well on first impression. If you are used to it however what a great horn. I do keep coming back to it for my own playing.
The other area where the bore of the instrument will vary significantly is at the smallest point of the leadpipe. This varies at right around the size of the average pencil so if you compare several leadpipes with pencils (clean the leadpipe first!) you will see that some are larger and smaller than others at this point. Older Conn 8D horns for example typically have a rather small bore at the smallest point of the leadpipe but these are again not considered to be small bore horns.
In any event, I try to use the term bore in the correct, specific way and keep focused in on the cylindrical part of the horn, through the valve section, which again on most horns is either .468 inch or 12 millimeter. In reality though makers have used sizes that are slight variations on these dimensions, depending on suppliers and such, and players will probably keep right on thinking bore mostly relates to the size of the throat of the bell.
