 The Clarinet BBoard
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Author: karlbonner82
Date: 2010-04-25 07:15
Anyone who has played clarinet and/or trumpet knows that the two instruments are regarded to have "cylindrical" bores while the other reeds and brasses are mostly conical. But, of course, the lower part of the trumpet's bore is very conical, as is the bottom third or so of the clarinet bore. In the case of brass, the main difference between more or less conical tubing is in the timbre (the more conical, the darker) but with reeds there is a fundamental 'night-and-day' difference between cylindrical and conical: only conical reed pipes can produce even-numbered partials (overtones).
So my question is: where is the dividing line between the "octave" pipes and the "twelfth" ones? In other words, how conical does the tubing have to be before the even-numbered partials appear? The clarinet's bore is not perfectly cylindrical so it seems as though even partials ought to exist in some minuscule quantity. If I had a single reed pipe whose bore was midway between that of the clarinet and saxophone, would it produce weak but existent even partials? And would its register key cause an octave jump or a twelfth jump?
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Author: Chris P
Date: 2010-04-25 09:26
Clarinets often have an expanding conical barrel and reverse conical bore at the top of the upper joint, but not nearly as reverse conical as a recorder, Baroque flute or piccolo bore - the widening/contracting is only in increments of fractions of a millimetre over a short length of the bore as opposed to a 1:40 taper over the entire length of the bore (which is an average oboe bore taper).
Former oboe finisher
Howarth of London
1998 - 2010
The opinions I express are my own.
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Author: Bob Phillips
Date: 2010-04-25 16:23
I've been messing about making spectrographs of the sound from my clarinet. I can find virtually NO even harmonics.
The power in the octave is down about 50-dB below the 12th for all of my mouthpieces.
I imagine that the reed's closing on the mouthpiece has a lot to do with keeping the even harmonics out of the sound spectrum. An oboe or bassoon reed probably does not close down completely --so the reflected wave goes down the bore as an expansion not a compression.
(Edited to add comment on reed control of overtone structure.)
Bob Phillips
Post Edited (2010-04-25 16:25)
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Author: Bassie
Date: 2010-04-25 17:37
>> where is the dividing line between the "octave" pipes and the "twelfth" ones?
This is an excellent question. My physics is a bit rusty, but I suspect that as a straight pipe is made more conical it will gradually 'fill in' the missing harmonics, until at some point a speaker vent in the right place will indeed overblow an octave.
There was a thread about a year ago about closed conical and cylindrical pipes. I recall that the conical pipe had all the overtones because the valid solutions for standing pressure waves are 'sinc' functions not 'sine' functions, sin(x)/x not sin(x).
I wouldn't be surprised if a 'good' clarinet is almost completely free of even harmonics.
EDIT: This brings us to the question of what exactly the clarinet bell brings to the instrument. I suspect the (~exponential) flare makes the 'open' end more 'open'...
Post Edited (2010-04-25 17:44)
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Author: RoBass
Date: 2010-04-26 12:32
There's an article written in the German Saxweb - The Pueton. The author inspected the geometrics for octaving instruments very well and explained it with some drawings...
There's only a very small range in conical shape to ensure a fine octaving.
kindly
Roman
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Author: Chris P
Date: 2010-04-26 13:53
A sax is basically an oboe with a single reed mouthpiece and behaves in the same way as an oboe - a double reed will close fully as a single reed/mouthpiece combo does when it's set into motion.
Likewise a single reed mouthpiece used on an oboe and bassoon will only have an effect on the tone, but the instrument will still behave in the same manner as if played with a double reed.
Are there any true reverse conical bore reed instruments (single or double) that have the same (or similar) bore taper as a Baroque flute/recorder/piccolo but with the reed/mouthpiece at the wide end?
The other day I put a tenor sax mouthpiece onto an EEb tuba to see what fundamental notes came from it (and to see how low it went!), and the harmonic series was standard for conical bore reeds - fundamentals, then overblew an 8ve, then a 5th, etc.
Former oboe finisher
Howarth of London
1998 - 2010
The opinions I express are my own.
Post Edited (2010-04-26 13:58)
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Author: Ken Shaw ★2017
Date: 2010-04-26 16:33
The experiment has been done. The result is the Octavin, which has a conical bore as close to cylindrical as possible while still overblowing at the octave. Unfortunately, it still sounds and blows like a saxophone, but is less stable, since it's at the edge of what's possible.
The instrument has been discussed a number of times. Search on octavin in the Clarinet and Klarinet archives to find it.
Ken Shaw
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Author: Gordon (NZ)
Date: 2010-04-28 04:46
Because of the lips and the reed, both a trumpet and clarinet act as pipes closed at one end. Therefore, both being basically cylindrical, they should overblow odd harmonics only.
A clarinet does do this. However in reality, a trumpet has harmonics that resemble those of a tube open at both ends, such as a flute or string, with all harmonics. I read somewhere that this is because of the long taper at the bell end, along with something to do with the shape of the mouthpiece, distorting the harmonics into being both odd and even. A masterly piece of design jiggery-pokery!
No wonder it does not sound like a odd-only harmonic instrument.
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Author: Ken Shaw ★2017
Date: 2010-04-28 13:38
Gordon -
Interesting. Is there a source on the net that describes how the trumpet works?
Ken Shaw
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Author: Koo Young Chung
Date: 2010-05-01 04:47
Main function of a clarinet bell is to match the impedance of a cylindrical tube.
When a tube is cut off suddenly without flare ,sound wave will be mostly reflected because of mismatch of impedance ,resulting not much energy is radiating to outside.
If you have a cylindrical clarinet (without a bell) with a couple of correctly placed tone holes below lowest E,then it'll play like a regular clarinet with a bell.
But it'll be longer than a clrinet with a bell.
Also it looks better.
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Author: Chris P
Date: 2010-05-01 09:44
Flutes don't have a flared bell - they are perfectly cylindrical throughout the body and footjoint sections (although the headjoint does narrow towards the top end).
Former oboe finisher
Howarth of London
1998 - 2010
The opinions I express are my own.
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