Bell shape vs sound

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bone-a-phone
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Bell shape vs sound

Post by bone-a-phone »

I'm kinda new to tuba, but ive played trombone for 40 years. Tuba has a lot more variables at play. Trombone bells don't change much from sackbuts with no flare to 11" bass trombones with lots of flare, and old peashooters kind of in between. I've noticed some tubas with huge flare, almost flat at the end, and some tubas with an almost straight conical shape with a tiny flare at the end.

I know as musicians we are supposed to pretend math doesn't exist even though it rules our lives and art. But the shape seems like a truncated parametric parabola, with some more or less truncated, or with various rates of change. The math figures into the design even if it doesn't filter down to the practitioners.

My question is how does bell shape affect the sound, and do tubists tend to develop a favorite shape? Does the shape of the bell figure into how you select an instrument? I know we have words to describe the sound like warm, foggy, dark, bright, focused, etc. But do we have corresponding language to describe the bell shape? Is there an acceptable canon of knowledge from the dreaded "freak jury" about the relationship between shape and sound? Or am I just being a stupid trombone player asking stupid questions?
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tylerferris1213
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Re: Bell shape vs sound

Post by tylerferris1213 »

Bell shape most definitely has an influence on sound. Some tuba makers offer 1 or 2 options for bell diameter on their instruments. Even a one inch difference is noticeable at the flare. Overall, I see a lot of people lean towards the slightly smaller bell option because it has a more "focused" sound. Lost is absolutely right. The larger bells, specifically large at the rim, have a "fluffier" or "woofier" sound. It's not bad. It's just not in fashion at the moment. That's just the bell diameter.

As a whole piece, the bell shape matters too. While there are many variables at play, I notice that tubas with a "stovepipe" bell have a much darker sound which is rich in fundamental. On the other end of the spectrum, the tubas which have a more rapid graduation in the bell (picture a Conn 2XJ) have a brighter sound that is rich in overtones. Again, there are many factors at play that have an influence on what comes out the bell, the bell being just one of them.
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Donn
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Re: Bell shape vs sound

Post by Donn »

It isn't entirely independent of listener position, as may be apparent if you consider the sousaphone's large bell flare.
toobagrowl
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Re: Bell shape vs sound

Post by toobagrowl »

Bell shape/taper has perhaps the biggest effect on overall sound color of any given tuba. The leadpipe, valve bore and outer bows also have an effect on sound, but the bell (and I'd argue the bottom bow) have the biggest influence on sound color. Big-flared bells tend to offer a more diffuse, mellow sound. But I have also found that the curve of the end of the bell flare has an effect on overtones. For instance, my 5/4 Meinl CC has a large-throated bell at 17.7". The end flare is modest, but has a noticeable 'curve' to it. This tuba has a dense, dark centered voice with somewhat bright overtones. Something like an Alex 163 is slightly smaller in size, but also has a large-throated bell at 16.5". But the end of the Alex bell taper is different - the 'curve' at the end of the bell is more gradual/more tapered and offers fewer overtones in the sound than the Meinl.
Big-throated bells with a modest flare tend to offer a denser/darker, more focused sound. But the size matters too. A smaller bell, no matter what taper/shape, will have a smaller sound than a larger bell. I am including the throat or bell stack when talking about bells.

Bell size & taper can have an effect on intonation, too. I took a 22" inch bell off a BBb and put a 19" bell on. The 19" bell had a smaller, more proportional taper to it. It tightened up the sound and improved the upper register intonation. With the old larger bell, the intonation was flat in the upper register near top/above the staff. The 19" bell fixed those pitch issues. :!:
I also swapped out the old large leadpipe and put a more moderate leadpipe on to improve response, but that is for another thread :P
bone-a-phone
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Re: Bell shape vs sound

Post by bone-a-phone »

cktuba wrote:These threads include the valuable insight of TubNet's resident genius (Rick Denney... who does not post nearly often enough anymore).

viewtopic.php?p=340871" target="_blank" target="_blank

viewtopic.php?p=258624" target="_blank" target="_blank

Thanks, that was excellent reading.
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Re: Bell shape vs sound

Post by TheGoyWonder »

Sousaphones can sound fine with a semiskilled operator, and they have a gigantic bell flare. I don't think the near-horizontal flange-like portion of the flare "does" anything.
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Re: Bell shape vs sound

Post by Donn »

If it doesn't do anything, that's a fair amount of weight to carry around just for looks. On the other hand, if the flare has the effect that it's widely supposed to have, diffusing the sound, then it makes a lot of sense on a sousaphone, and on bell front tubas (which I believe do tend to have wider flares also.)
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