TubeNet

In Brassmusic on-line magazine by Ian Church, "Sousaphone-ologist" (AKA KiltieTuba )

Pretty awesome! Nice job Ian!

Useful article, Ian. But don't you think that the quote from H.N.White Co.:

The low frequencies from a BBb tuba are generated by a column of air that’s about 36 feet long… 18 feet of which are INSIDE the horn and another 18 feet that’s OUTSIDE the horn.

may be a little misleading. True the end effect extends the effective vibrating length of the air column on the order of the size of the bell, but not by another 18 feet? I suppose they probably meant the wavelength of the fundamental is twice the length of the open tube.

Souzys RULE! I had a lot of fun reading this article.

Nice Job!!! Ian ... Good work... I am happy you did this
Thanks Harv.

DonShirer wrote:Useful article, Ian. But don't you think that the quote from H.N.White Co.:

The low frequencies from a BBb tuba are generated by a column of air that’s about 36 feet long… 18 feet of which are INSIDE the horn and another 18 feet that’s OUTSIDE the horn.

may be a little misleading. True the end effect extends the effective vibrating length of the air column on the order of the size of the bell, but not by another 18 feet? I suppose they probably meant the wavelength of the fundamental is twice the length of the open tube.

Actually, Don.... a tuba isn't EXACTLY 18 feet long, either. That statement may be a little bit misleading but it's a descent illustration of the fact that the fundamental wave length of a low BBb is about 36 feet... about 18 feet of which is the horn itself.

Nice job on the paper, Ian.

TubaTinker wrote:Actually, Don.... a tuba isn't EXACTLY 18 feet long, either. That statement may be a little bit misleading but it's a descent illustration of the fact that the fundamental wave length of a low BBb is about 36 feet... about 18 feet of which is the horn itself.

It's worse than that. The conical bore of the tuba causes the wavelength of the note to change as the pressure fronts progress through the instrument. The straight organ-pipe models just don't work with conical instruments, and there is almost no way to simplify things mathematically and retain accuracy. The only thing you know is that the pressure peaks are about 36 feet apart with a pedal Bb, and the pressure minimum in between them is just a little outside the bell. But it is not exactly halfway between those pressure peaks, because the wavelength changes in the half that is inside the tuba. The frequency domain can be a complicated place.

Rick "whose Miraphone measures longer than 18 feet when the bell effect is included" Denney

Rick Denney wrote:

TubaTinker wrote:Actually, Don.... a tuba isn't EXACTLY 18 feet long, either. That statement may be a little bit misleading but it's a descent illustration of the fact that the fundamental wave length of a low BBb is about 36 feet... about 18 feet of which is the horn itself.

It's worse than that. The conical bore of the tuba causes the wavelength of the note to change as the pressure fronts progress through the instrument. The straight organ-pipe models just don't work with conical instruments, and there is almost no way to simplify things mathematically and retain accuracy. The only thing you know is that the pressure peaks are about 36 feet apart with a pedal Bb, and the pressure minimum in between them is just a little outside the bell. But it is not exactly halfway between those pressure peaks, because the wavelength changes in the half that is inside the tuba. The frequency domain can be a complicated place.

Rick "whose Miraphone measures longer than 18 feet when the bell effect is included" Denney

And this is one reason why, for example, the 5th partials can be really flat on some tubas, only somewhat flat on others, and actually be in tune on even others. And since they all interact, there's no way to really adjust one spot in the horn for one note without really affecting a bunch of other notes that may interact directly with that particular spot also.

Nice article Ian. Very comprehensive.

Yeah but I didn't want to go into details about the waves in the horn, my beef was in the part of the original quote that emphasized the region outside the horn which (again simplifying) is NOT part of the resonating column but an outgoing wave spreading out towards Infinity (Infinity is my brother-in-law, a baritone player). Bloke inadvertently had it right, the quote was "descent", i.e. it smelled slightly until it was further explained.

Sorry if this thread is diverting attention from your interesting article, Ian.

Ian, you write really well, and your love of tubas and joy of learning (and sharing and teaching) stands out.

Talking the the 36 foot wave length (or whatever amount it actually is), is this effected by size, or pitch of tuba? My observation is that a 6/4 tuba is more affected by limited space for the sound to develop than a 4/4, but cannot explain why that should be?

Ian, I was interested by your statement;

Furthermore, the introduction of the Conn 20J in 1934 coincided with the discontinuation of their Grand Jumbo line, also in 1934.

Did production of 'Jumbo' size sousaphone by manufacturers other than Conn continue after 1934? Are you implying that 6/4 size tubas in the view of the manufacture's replaced the Jumbos?

Neptune wrote:Talking the the 36 foot wave length (or whatever amount it actually is), is this effected by size, or pitch of tuba? My observation is that a 6/4 tuba is more affected by limited space for the sound to develop than a 4/4, but cannot explain why that should be?

A 6/4 tuba, with its larger girth, can, under the right acoustics, produce more fundamental. The smaller the tuba, generally the less fundamental. The overtones are about the same, although as Rick Denny points out on his website, construction differences cause balance of overtone distribution differences.

The bottom line is that if you're used to hearing a 6/4 in a large hall where the fundamentals can propagate properly, it sounds magnificient, and when that same tuba is taken into a smaller room, it will sound thinner because there is not enough room for the fundamental to propagate, and all you get are overtones, which could even be truncated in their development because of the large bore and bell throat.

OTOH, if you're used to any number of standard sized 4/4 tubas that only have moderate fundamental development, but a wide range of overtone development, it's not going to be as much as a contrast going from a large hall to a smaller venue.