Posted by K on April 16, 2003 at 16:24:06:
In Reply to: The physics of a tuba mute posted by Karl on April 16, 2003 at 15:43:22:
Be sure I can not give a very technical respons, as I simply don't know the terms in English:
Instruments with relatively small bell flares and small bell throat volumes need longer tubes to produce the exact same pitches as comparable instruments with wider flares and larger bell throat volumes.
The wide flares and throats seem to have a sort of "shading" effect a good deal beyond the physiucal end of the physical tube lengths.
That has a least two effects:
such instruments (at least to me) slot less narrowly intonationwise.
such instruments needs mutes, that at least protrude sufficiently beyound the end of the bell, so that they physically will cover the tube length, which the open instruments cover with their bell-shading effect.
As for missing notes foolowing the application of certain mutes:
On trombones (tenor and bass) I am a great fan of my circa 1970 Tom Crown aluminium (and a copper bowl in the tenor model) straight mutes.
I once read an article featuring Tom Crown. He had worked together with Mr. Kleinhammer, who had tested the bassbone prototypes.
Tom Crown had had an idea about remedying a weak point of metal mutes: their being very dent prone at the edge of the opening. So he had made a prototype, which had that edge reinforced by folding the metal back, so that the edge area had the strength of two layers of metal for an inch or so.
Mechanically and dent profylactic the idea worked beatifully. But Mr. Kleinhammer lost some of his low notes. As soon as he was provided a prototype with only a single layer of metal, and hence a sharper edge, he again had all notes available.
And then the thickness/strength of the cork/rubber spacing strips also is considered to have a very determining effect on parameters like intonation and response. The standard thickness at delivery from new almost always can be considered to be oversize. I modify them with a very sharp knife in small increments with test playing in between. Sometimes I have taken too much off. No problem. I just mount new spacers made out solid wine corks.
I do not recommend adjusting the thicknes by means of sandpaper. Some of the sand will inevitably be embedded in the cork. And over time it will grind its way into the inside of your bell.
I don't know, whether this is helpful to you, but this is what I have experienced over several decades with mutes.
Klaus