Welcome, Guest. Please login or register.

Login with username, password and session length

 
Advanced search

1087332 Posts in 72017 Topics- by 19243 Members - Latest Member: CABurton159
Jump to:  
Pages: [1] 2  All   Go Down
Print
Author Topic: Theory questions about bell shapes  (Read 3383 times)
0 Members and 1 Guest are viewing this topic.
Whitbey
*
Offline Offline

Location: Rochester MI USA
Joined: Apr 14, 2000
Posts: 955

View Profile WWW
« on: Sep 05, 2004, 08:31PM »

Over the years I have noticed the shape of the taper of trombone bells varies. It seems that the 547 and 562 horns have a little variety but not very much. Even when the bell flare is bigger the rest of the bell seems the same shape. Of the 547’s the King 4b seems to have the most different bell shape. Seems like the King was bigger between the tuning slide and the bell brace. Over the years I have seen a few small bore horns of a very old vintage that had a shape that was a lot bigger between the tuning slide and the bell brace then had a smaller bell rim. Almost euphonium like.
Anybody have a horn with a different bell?
How is it different and how does it play?
Has anybody else noticed these bell shapes?
Notice a sound difference?
Was it on a small jazz horn or a big horn?

My curiosity is looking for is how bell shape impacts:
The overtones and the sound.
The intonation of the partials.
The ability to project the sound.

Logistically it is noteworthy that having more than one shape of bell must be a bad thing as it seems that it is not done. But on the other hand if two brands of horn use a different shaped bell and they both play well you start to wonder why more bell shapes are not made available.

I personally do not want to change my horn. This post is asking the questions just to learn more about how horns work. Please post your best observations so we can all be more informed about how our horns work.
Logged

See my profile for my horns. To long to put on each post.
Dan H.
He doesn't know how to put this, but he's kind of a big deal

*
Offline Offline

Location: Saratoga Springs / Potsdam, NY
Joined: Apr 16, 2003
Posts: 2600
"Conquer the devils with a little thing called love"


View Profile WWW
« Reply #1 on: Sep 05, 2004, 08:46PM »

It seems to me that the reason many older horns appear to have such a large throat and small flare is due to the fact that many older trombones have very small bells compared to many trombones of today. I think that as bells gradually got bigger, the flares were the main part of the bell to see an increase in size, with the throat seeing less of a change for the most part.
Logged

- Daniel Havranek
elmsandr

*
Offline Offline

Location: Howell, MI
Joined: Apr 12, 2004
Posts: 3324

View Profile
« Reply #2 on: Sep 06, 2004, 06:23PM »

FWIW, Edwards basses are available with two different bell tapers.  Though most all of their popular bells come off the same mandrel.  The less popular one has a more compact throat.

I think that some older Conns had a significantly different taper than is currently available.

Cheers,
Andy
Logged

Andrew Elms
Mahlerbone

*
Offline Offline

Location: Newington, CT
Joined: Nov 16, 2002
Posts: 3494

View Profile
« Reply #3 on: Sep 06, 2004, 07:11PM »

I do know that Shires basses are available with two different throat tapers also.  The narrow taper  is Conn-style, and the wider taper is Bach-like.  As you could well imagine, the wide Bach-style taper produces a very broad sound.

I'm not sure if Rath makes bells that come in different tapers.  Never really looked closely at the one on mine.  But it doesn't really matter, all I know is that it sounds really darn good, and that's good enough for me. :)
Logged

Shires alto w/ yellow bell
Shires T00NLW, 1YM8, 1.5 tuning slide
Shires TB47G, 7YLW, TY tuning slide, standard rotor
Shires B62LW, BI 2G, Bollinger tuning slide, dependent Trubores
timothy42b
*
Offline Offline

Location: Colonial Heights, Virginia, US
Joined: Dec 7, 2000
Posts: 12311

View Profile
« Reply #4 on: Sep 07, 2004, 03:02AM »

Did you ever go out to the parking lot and try your key in three or four cars before you got to your own?  Wonder why?  

Because over the years, the designs have all converged on the same optimal shape, and the cars all look the same.  I was talking to an auto industry design engineer once, and complained about it, and he said they all should look the same, they are all getting close to perfect.  Except for high end or special purpose vehicles, of course, and even they tend to be the same - how many shapes of SUV are there?

It's probably the same with trombone bells.  There used to be a lot more variation, but what works maybe ends up looking pretty much the same.

I would like to see a "dual" made, though.  That would look classy.
Logged

Tim Richardson
David Gross
*
Offline Offline

Location: Sudbury Massachusetts
Joined: Mar 10, 2002
Posts: 3377

View Profile
« Reply #5 on: Sep 07, 2004, 04:50AM »

Quote from: "timothy42b"
Did you ever go out to the parking lot and try your key in three or four cars before you got to your own?

It happened to me once. My key actually unlocked the door of a car that looked almost the same as mine. If the stuff on the back seat hadn't been foreign to me I would have driven off with the wrong car!
Logged

Dave

Money talks. Mine says "Bye bye!"
David Gross
*
Offline Offline

Location: Sudbury Massachusetts
Joined: Mar 10, 2002
Posts: 3377

View Profile
« Reply #6 on: Sep 07, 2004, 04:54AM »

The bell flare affects the intonation. Get it wrong and the partials don't line up.
Logged

Dave

Money talks. Mine says "Bye bye!"
timothy42b
*
Offline Offline

Location: Colonial Heights, Virginia, US
Joined: Dec 7, 2000
Posts: 12311

View Profile
« Reply #7 on: Sep 07, 2004, 05:13AM »

Quote from: "David Gross"
The bell flare affects the intonation. Get it wrong and the partials don't line up.


True to a certain extent.  But it should be obvious that the lineup of partials has a bigger effect on tone than intonation.  Overtones are forced to line up when playing, it is a mathematical requirement.  Partials do not line up, and this is affected by more than just the bell.
Logged

Tim Richardson
Whitbey
*
Offline Offline

Location: Rochester MI USA
Joined: Apr 14, 2000
Posts: 955

View Profile WWW
« Reply #8 on: Sep 07, 2004, 12:39PM »

I wonder if a bigger throat of the bell is similar to or has a similar impact on the horn as a dual bore slide or tuning slide in the hand slide rather than the bell.
Logged

See my profile for my horns. To long to put on each post.
Liche
*
Offline Offline

Location: Oxford, UK
Joined: Apr 24, 2002
Posts: 500

View Profile
« Reply #9 on: Sep 08, 2004, 03:15AM »

I did some experimentation a while back using theoretical bells (actually for trumpets, but the principles are similar) on various horn shapes and looked at their input impedance plots (plane-wave TL model). Modelling a trumpet as a cylinder connected to a flaring bell (i.e. without valves or bends), the following effects were observed:

(listing effects of the parameter being increased; decreasing has the opposite effect. Flat/sharp is intonation (freq.), raise/drop is impedance magnitude, low/middle/upper is the register on the instrument)

Cylinder:
length: flatten all peaks
bore radius: drop all peaks

Taper-end of bell:
flare: slight shuffle of lower peaks (i.e. moved in different directions)

Middle part of bell:
flare: slight shuffle of middle peaks
bore radius: flatten lower peaks

Mouth of bell:
length: flatten all peaks
flare: sharpen all, drop upper peaks
input radius: sharp lower, flatten middle, drop upper
output (bell) radius: raise upper, drop extreme upper


None of this is to be taken as absolute truth (don't design instruments on this basis yet!) both due to restrictions in the phsyical model and the use of a trumpet design. I intend to do something similar with trombones at some stage, and I will additionally be using some much better physical models in the next six months.

For reference, I'd describe dual-bore slides as having both a flattening and a 'shuffling' effect.

Note also that the changes to these parameters were kept reasonably small and measured in isolation - a combination of factors will have cumulative results. Using these few rules I was able to match a (idealised and theoretically-calculated) target impedance curve pretty closely in 5-7 steps. I've developed computer optimisation routines that can do this very well (but, as yet, are limited in usefulness by the physical model).
Designing bells is a very tricky business!

Also it should be noted that differences of ~1mm mid-bell are enough to have a noticeable effect on the impedance curve, yet are surely too small to discern when comparing two different bells visually.
Logged
actikid
*
Offline Offline

Location: Indianapolis
Joined: Dec 30, 2001
Posts: 10552

View Profile
« Reply #10 on: Sep 08, 2004, 05:37AM »

Quote from: "timothy42b"
Quote from: "David Gross"
The bell flare affects the intonation. Get it wrong and the partials don't line up.


True to a certain extent.  But it should be obvious that the lineup of partials has a bigger effect on tone than intonation.  Overtones are forced to line up when playing, it is a mathematical requirement.  Partials do not line up, and this is affected by more than just the bell.

I think there are two different issues here:

a) when playing a single note, how compatible are the various overtones?  Let's call this harmonic alignment.

b) when playing the "bugle series" of notes in a given slide position, how compatioble are those notes?  Let's call this alignment of partials.

Coincidentally I was playing my double-bell euph in the longest gig of my life last evening (5 hours).  Through boredom or whatever I used the trombone side of the horn more than usual.  It is hard to hear the harmonic alignment in ensemble.  But the alignment of partials is horrendous on this thing.  The upper notes are very flat and the lower notes are impossibly sharp.  It is off by more than a half step per octave.

But don't blame the bell entirely.  It seems to be the relationship of bell to the cylindrical bore size (which is oversized in this case obviously).  And more than that, the mouthpiece can have a huge effect on the alignment of partials.  I've selected a mouthpiece that is best suited for the euphonium side of this instrument.  That makes the alignment of partials much worse than it would be with a smaller mouthpiece.
Logged

Where was Blackwater on the morning of September 11, 2001?
Whitbey
*
Offline Offline

Location: Rochester MI USA
Joined: Apr 14, 2000
Posts: 955

View Profile WWW
« Reply #11 on: Sep 11, 2004, 05:18PM »

Thanks for all your posts.
We are all a little more informed.
Great comments!
Thanks
Logged

See my profile for my horns. To long to put on each post.
actikid
*
Offline Offline

Location: Indianapolis
Joined: Dec 30, 2001
Posts: 10552

View Profile
« Reply #12 on: Sep 12, 2004, 09:45AM »

More on the subject of harmonic alignment.  Friday and Saturday, I played big band jobs on a new Kanstul 1662i bass (Mike Suter model).  With continuous taper bell and tuning-in-slide, I believe this instrument is patterned closely after the Conn 62.

There are several remarkable facets to this horn, but I think the most remarkable quality is something I didn't expect at all. It is especially easy to hear intonation.  Every note seems to have a clearly defined pitch you can hear immediately without any ambiguity.

On other instruments, it is sometimes a struggle to really hear exactly where the true pitch lies.  I'm trying to figure out why this instrument is different.  It could be that the horn just gives the player louder feedback.  However, I'm thinking there is more to it than this.  My current theory is that the harmonics are particularly well lined-up on this horn.

Let's say on a hypothetical instrument, the first overtone is a little flat relative to the fundamental.  And maybe the second overtone is a little sharp.   Which pitch does the ear hear?  The fundamental has more decibels, but human hearing is attracted to the higher pitches, so there could be a struggle discerning the pitch center.  

I'm thinking that is why this Kanstul is easier for me to play in tune.  I'm thinking that the overtones line up more accurately than the average instrument, thereby allowing me to hear the real pitch immediately.

Anybody have any ideas about this?   Do you find some instruments are easier to play in tune?
Logged

Where was Blackwater on the morning of September 11, 2001?
timothy42b
*
Offline Offline

Location: Colonial Heights, Virginia, US
Joined: Dec 7, 2000
Posts: 12311

View Profile
« Reply #13 on: Sep 13, 2004, 11:36PM »

Quote from: "actikid"

Let's say on a hypothetical instrument, the first overtone is a little flat relative to the fundamental.  And maybe the second overtone is a little sharp.   Which pitch does the ear hear?  The fundamental has more decibels, but human hearing is attracted to the higher pitches, so there could be a struggle discerning the pitch center.  


Anybody have any ideas about this?   Do you find some instruments are easier to play in tune?


You're probably on to something but I don't think this is quite it yet.

When you play, your overtones line up perfectly, mathematically.  The overtones of forced vibrations will always be integer multiples, regardless of whether the individual partials would be sharp or flat.  

If the individual partials are close to the overtone pitch, those overtones should be reinforced more.

There's a confounding factor.  How tight is the slot?  Right at resonance, you get pretty good response, but when you move a short enough distance away, you still get response.  Some horns are almost flat.  

Can a horn have a very narrow slot for some partials, and not for others?  

If your slot is TOO tight, and your upper partials not right on, then your overtones may miss them.  If it's too loose, they'll all hit, but none of them very cleanly.  Probably one of those mini-max problems.
Logged

Tim Richardson
actikid
*
Offline Offline

Location: Indianapolis
Joined: Dec 30, 2001
Posts: 10552

View Profile
« Reply #14 on: Sep 14, 2004, 04:17PM »

Quote from: "timothy42b"
When you play, your overtones line up perfectly, mathematically.  The overtones of forced vibrations will always be integer multiples, regardless of whether the individual partials would be sharp or flat.  .
That's true in theory, but I'm not convinced it is true in the real world.

The bell flare shape certainly can make a big difference on how the partials stack up.  That is, one bell shape may allow the tuning Bb and the Bbs and octave above and below to be right on the money, whereas another horn (another bell flare shape) might throw the higher or lower pitches off.

Indeed, that is the driving purpose behind the bell flares in the first place.  The shape of the flare directly affects intomation BETWEEN notes.  We all agree on that, right?  

Given that, it stands to reason that the bell flare would have exactly the same effect on overtones.  In other words, there is no reason to believe a bell flare shape would affect the fundamental pitches, but not the overtones.

Maybe I'm not making a very rigorous argument here.  From the driver's seat, I just know that I have a lot of trouble hearing intonation on most bass trombones, especially below the staff.  And on this Kanstul, the pitch seems to come through clear as a bell (bad pun intended).
Logged

Where was Blackwater on the morning of September 11, 2001?
Whitbey
*
Offline Offline

Location: Rochester MI USA
Joined: Apr 14, 2000
Posts: 955

View Profile WWW
« Reply #15 on: Sep 14, 2004, 06:21PM »

Odd question.
If the tuning slide is in a bad place. And tuning in the slide is just a lot of things to go wrong or slow you down.
Why not have one tuning slide just beyond the F valve area and have a moveable brace with a set screw?
I have seen this on trumpets and they aren’t any smarter than we are.
This would give all but 5 or 6 inches of the bell section for a taper and leave the hand slide alone.
The only problem would be when you move the tuning slide the bell would move. Might not be able to find 3rd or 4th position until you stopped the crutch grab.
Logged

See my profile for my horns. To long to put on each post.
timothy42b
*
Offline Offline

Location: Colonial Heights, Virginia, US
Joined: Dec 7, 2000
Posts: 12311

View Profile
« Reply #16 on: Sep 14, 2004, 11:28PM »

Quote from: "Whitbey"
Odd question.
If the tuning slide is in a bad place. And tuning in the slide is just a lot of things to go wrong or slow you down.
Why not have one tuning slide just beyond the F valve area and have a moveable brace with a set screw?
I have seen this on trumpets and they aren’t any smarter than we are.
This would give all but 5 or 6 inches of the bell section for a taper and leave the hand slide alone.
The only problem would be when you move the tuning slide the bell would move. Might not be able to find 3rd or 4th position until you stopped the crutch grab.


You could do that.

Or just have the leadpipe slide in and out, like the fluegel horns do.  

I don't see why that wouldn't work fine.  Most people do not make large tuning slide adjustmenst from day to day anyway.
Logged

Tim Richardson
Pieter
*
Offline Offline

Location: Netherlands
Joined: Mar 27, 2004
Posts: 545

View Profile
« Reply #17 on: Sep 14, 2004, 11:47PM »

Quote from: "timothy42b"
Quote from: "Whitbey"
Odd question.
If the tuning slide is in a bad place. And tuning in the slide is just a lot of things to go wrong or slow you down.
Why not have one tuning slide just beyond the F valve area and have a moveable brace with a set screw?
I have seen this on trumpets and they aren’t any smarter than we are.
This would give all but 5 or 6 inches of the bell section for a taper and leave the hand slide alone.
The only problem would be when you move the tuning slide the bell would move. Might not be able to find 3rd or 4th position until you stopped the crutch grab.


You could do that.

Or just have the leadpipe slide in and out, like the fluegel horns do.  


That would be annoying, all the slide positions are further away whenever you tune your horn a bit flatter!
Logged
timothy42b
*
Offline Offline

Location: Colonial Heights, Virginia, US
Joined: Dec 7, 2000
Posts: 12311

View Profile
« Reply #18 on: Sep 15, 2004, 12:14AM »

Quote from: "actikid"
Quote from: "timothy42b"
When you play, your overtones line up perfectly, mathematically.  The overtones of forced vibrations will always be integer multiples, regardless of whether the individual partials would be sharp or flat.  .
That's true in theory, but I'm not convinced it is true in the real world.

<snip>

Given that, it stands to reason that the bell flare would have exactly the same effect on overtones.  In other words, there is no reason to believe a bell flare shape would affect the fundamental pitches, but not the overtones.



Maybe I didn't explain what I meant very well.

Or, maybe you disagree.  If I read Benade correctly, you are in good company.  But I think he got this one wrong.

Pluck a violin string.  The overtones won't line up mathematically, they will line up at the natural higher modes of vibration, exactly like partials on the trombone.  They can be way off, depending on how stiff the string is.  

Now bow it.  The overtones are forced to line up mathematically.  

The same is true of trombone.  If you lip slur up the partials, the fundamental at each partial will sound.  The overtones will too, but ignore them for a moment.  If you play the pedal and listen to the higher overtones, they will not be the same series as the partials.  The overtones on trombone, just like the violin, are forced to line up mathematically, even though the partials are a long way from this.  This is a conseequence of the mechanism that produces the upper harmonics from a basically sinusoidal motion of the embouchure - I do not see how it can be otherwise.  

So the overtone series for a given note does not match the partials available above that note.  

The bell shape affects the way the partials line up, we agree on that.  Theoretically then it should affect which of the overtones should be reinforced.  But it can't change the actual frequencies of those overtones, only the relative strengths.  

I know that doesn't really affect your premise, which is that certain bell shapes favor easy tuning horns, but I saw an opportunity to attack some old confusion.  

Benade has a procedure for adjusting a trumpet mouthpiece by playing the second partial and listening to the third, and opening the backbore until they line up.  I do not understand how this is possible.  It would appear from spectral plots that this never happens.  Maybe I misread him.
Logged

Tim Richardson
Whitbey
*
Offline Offline

Location: Rochester MI USA
Joined: Apr 14, 2000
Posts: 955

View Profile WWW
« Reply #19 on: Sep 18, 2004, 07:28PM »

An update on the horn watching front. A friend showed up with her Larry Minick small bore tenor.
Interesting how the bell on the Larry Minick is about 7” and my 547 Edwards is 8-1/2” and at the bell brace the Larry Minick is a strong ¼” bigger than my 547 Edwards.
The Larry Minick has a great focused sound and is very responsive.
 Seems funny to me that a bell throat on a small horn is bigger than a big horn.
Logged

See my profile for my horns. To long to put on each post.
Pages: [1] 2  All   Go Up
Print
Jump to: