Shape of the Bell/Tubing

[Kevin Hendrick]

(generalization, but...) Bells that pancake out (flat) at the end tend to sound more "fluffy" and bells that do not have that feature tend to sound more blatant.

Yes, I already know this....
But what about the shape of the bell, especially near the rim? One of the music shows (Musikmesse or whatever that is), if I recall correctly, had a euphonium with a really oddly shaped bell rim - I think it was like a flower.
Essentially, if the bell was less conical, but more square, how would it effect the tone?

Ah, more like one of these:

http://www.serpentwebsite.com/SQPT_concept.htm

The author seems to indicate not much difference (and provides .mp3 files) -- the plans are free downloads & the materials relatively inexpensive (would make the try-it-and-see approach more practical). Hope this helps!

[Dan Schultz]

I wouldn't exactly consider recording bells to be concentrically 'round'. Does that matter?

A 'squashed' bell would be really tough to manufacture.

[Dan Schultz]

' you mean like this...??

WOW, Joe... did you make that? Out of an old Buick or something?

[Kevin Hendrick]

' you mean like this...??

WOW, Joe... did you make that? Out of an old Buick or something?

Nice! Isn't that where they got the inspiration for Lombard Street?

[imperialbari]

The late Fred Marzan had tubas made to his concepts by at least two European makers, Willson and Böhm & Meinl.

At least some of the B&M made CC tubas with upright bells had some intonation issues. My own B&M made York Master BBb is not built after the Marzan concept, yet it shares the two part bell and maybe the bottom bow and some of the branches with the Marzan CC.

When I once read some gross whining over the funny pitches of a Marzan CC, I urged a test where the upright bell was replaced by a recording bell like the one on my BBb. The large B&M tubas use conical collars, so getting an alternative bell isn’t always easy. Yet somebody owned a Marzan CC as well as a York Master recording bell and tested that non-standard set-up. The intonation improved from the change of bell.

My point is: tubas are designed for either bell-up or for recording bell. The two bell formats act differently.

Klaus

[Donn]

BTW; I don't remember ever hearing of a direct, side by side comparison between a 38 K and a 20K, so I don't know if anyone has ever
proven that all 20Ks have quirky intonation due to the flattening of the ports.

Indeed, you might even find a recent assertion to the contrary on this forum, that the 38K and 20K both suffer from flat F. I'm on the other side, since I have a 40K (like 38K) and the partials work for me, but even if it's due to the valve section, I wouldn't be too sure that's about the oval shape per se.

I would imagine that all those bends in the tubing, for example, would be at least as irregular acoustically as the oval passage through the valves.

(By the way - not that it's likely to help here, but - don't waste time with the site search function, for anything more than the most trivial stuff. It's terrible. Google search with site:forums.chisham.com isn't perfect, but it's better, though there's a little problem if you're searching for something that happens to show up in someone's "signature.")

[toobagrowl]

I, too, have wondered how diff. shaped non-round tubes and bells would affect sound, response and pitch for some time now.

http://www.serpentwebsite.com/SQPT_concept.htm

Those 3 samples all have a breathy, dull "wooden" sound......HOWEVER, I do like the contrabass "Patrick" model. I think "Patrick" could possibly be refined and actually be used in some modern music and be an addition to the "bass" instrument family (tuba, string bass, bass clarinet, contrabassoon, etc.)

[Rick F]

That's Sterling's (one-of-a-kind) 'Yorkshire Rose' model and was on display at ITEC 2008. Here's a picture of Charley Brighton (aka Highams) playing it at ITEC. Not sure if he ever posted a review of his findings on tone or response. I remember reading the the bell was made of pretty heavy material.

[Elbee]

Still essentially round though within the definition of bell shape?

[Rick Denney]

Just a quick drive-by to post a comment on this topic. Sorry to be scarce, but time commitments are extreme right now and I just got back from Alaska.

The bell acts as an impedance matching device. It provides a way for the important overtone frequencies to transfer efficiently to the free air outside the instrument rather than running into a (frequency) wall and reflecting back. Each portion of a flared bell works on a different frequency. Thus, if you remove a significant sector of the bell (as you with with a triangular shape), it will affect the efficient transmission of overtones at the frequencies matched by that angle of the bell flare. I rather doubt that angles beyond about 45 degrees have much effect on the timbre, however. The Sterling bell does not have deep enough penetrations into the round shape to make that much difference, I would not expect.

The bell also acts as a directional amplifier, and the directionality is highly dependent on the shape. The wider and more circular the bell, the wider the dispersion--I believe--as exemplified by loudspeaker reflectors. The narrower and more exponential the shape, the narrower the dispersion and the greater than directionality. I believe this accounts for the differences in the way tubas in the American and German traditions propagate sound in a concert hall more than anything. I don't think a decoratively shaped bell ala the Sterling would affect that much.

Rick "for whom the bell tolls" Denney