 The Clarinet BBoard
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Author: Andy
Date: 2001-02-03 05:11
Hey Guys,
I was given a Buffet poster the other day with a heap of Clarinets on it. I was about to put it in the cupboard for a while when I noticed that the A and the Bb elite are the same length in the photo! I checked it and saw that although the keys are in different places the lower joint on the Bb is extended much more then the A so as to make them both the same length. Can someone please explain this to me! Does it have anything to do with the extra key? I am completly lost as it has thrown all ideas I had about acoustics out the window!
Thanks in advance,
Aussie Andy
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Author: Eoin McAuley
Date: 2001-02-03 07:11
If the Bb has a "low Eb" key and the A doesn't, then they should be exactly the same length. Each of them has the same lowest note, which is actually concert pitch Db, but is called Eb on a Bb horn and is called E on an A horn. Since the lowest note has all the holes closed, the length of the horn is the only thing that affects its pitch. The only difference between the two horns is where the holes are drilled. Everything in the Bb will be moved further up towards the mouthpiece.
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Author: Mark Charette, Webmaster
Date: 2001-02-03 14:10
The formula for the 1st resonant frequency of an air column is
f=v/4(L + 0.4D)
where v is the local velocity of sound, L the length, and D the diameter.
Therefore you can change the key by changing the diameter without changing the length - even without a low Eb on the Bb clarinet. In most cases the length and bore are both changed to keep the instrument in tune with itself in the different registers, and is why the "polycylindrical bore" which helps particular tuning problems was invented (and is why it works at all). The tone hole chimneys add to the effective diameter, too, which is why people put tape in them to help with tuning. It's not completely magic - there's a reason.
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Author: Ken Shaw
Date: 2001-02-02 17:50
Andy -
I played a new Buffet Elite at a recent show in New York. Unlike the original Elite, it had the extra hole and key mechanism at the bottom. However, it did not have a low Eb key. The mechanism is attached to the register key and fixes a problem with intonation and resonance on the low E and middle B. With the mechanism, they don't have the blaring "bell" sound. The instrument played very well, with a big, resonant tone. (I had someone hold down the key while playing low E and middle B, to see if it gave Eb/Bb, but the intonation was way off, so the mechanism is just for resonance and tuning.)
They did not have an Elite in A at the show, so I don't know whether the mechanism has been added to that model.
A "resonance" hole at the bottom is not uncommon. It's available as an option on the Selmer Recital A clarinet, and most German and English clarinets have a vent hold near the top of the bell. You can see it in most pictures of Dieter Kloecker.
Best regards.
Ken Shaw
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Author: Terry Horlick
Date: 2001-02-03 15:57
<BODY BACKGROUND="/Images/bkg.gif" LINK="#0000FF" ALINK="#FF0000" VLINK="#330000" onload="loadpage()">
<FONT FACE="Arial,Helvetica,Sans" SIZE="+3" COLOR="#008000">
<B>Mark, that answers a lot of questions for me. Can you explain two things for me, please?</B></FONT>
<FONT FACE="Arial,Helvetica,Sans" SIZE="+2" COLOR="#008000">1)</FONT> What is the exact shape fo the Poly Cylindrical bore. I know clarinets aproximate a cylinder and resonate like a cylinder stoppered in one end, but when you look at the bore it is indeed shaped like a cone with the apex truncated. The bore diameter at the barrel is much smaller than the bore at the bottom end of the body. It appears to taper smoothly.
A true cone will have a complete overtone series like a saxophone or trumpet. The clarinet seems to skip every other overtone. In other words, a saxophone acts like a cone and a clarinet acts like a cylinder. They both look like cones inside only the clarinet has the mouthpiece placed so as to form a truncated cone. Why would this remove half of the overtones? I've wondered this since high school (30 years) and have never asked.
<FONT FACE="Arial,Helvetica,Sans" SIZE="+2" COLOR="#008000">Thanks, Terry</FONT>
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Author: Mark Charette
Date: 2001-02-03 20:06
Terry,
Polycylindrical just means that the clarinet is made up of more than one cylinder, with a "step" in between them. The flare at the bottom isn't where the sound comes out (except for the long tones) and the upper/lower joint difference in the bore size doesn't flare enough to be considered a cone acoustically.
A cone accentuates even overtones (the register keys allow an even node to be vented, which is why they overblow in octaves. The cylinder accentuates the odd overtones, so the register key overblows the 12th.
Cones contain some odd harmonics, and cylinders contain some even harmonics, but it's the preponderance of the overtones that generates the classic sounds.
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Author: Terry Horlick
Date: 2001-02-03 20:41
</BODY><BODY BACKGROUND="/Images/bkg.gif">Mark,
Thanks for the interesting information. I always thought that the cone delivered every overtone (odds and evens), while the cylinder just the evens. So on a sax you get teh octave and then a fourth above theat (the twelveth). The clarinet skips that octave and pops right to the twelveth.
It is interesting that the "octave" vent on a sax is coupled so you use two different vents depending on what are of the horn is in play. This puts the vent near the middle of the air column (lower for low notes, higher for high notes) so thet the first overtone (first frequency node) is excitied. I have also been wondering why the clarinet doesn't do this, I figured that by trying for the second frequency node you need the vent 1/3 of the way down the air column. I just assumed keeping the vent up near the barrel put it up near the 1/3 point for most notes.
Re. poly-cylindrical bore: I thought there might really be "2 cylinders " of differing diameters, but as you said the bore is tapered. I just can't see where the "step" is between these bores. Is there really a step in there or does the gradual taper change slope somewhere in the bore. As I mentioned I just obtained a one piece horn, if a polycylindrical bore horn were made in one piece houl a "step" be visible somewhere inside that bore. (I am assuming that I can't see the step as it occurs at the middle joint...even so I don't see it while sighting down the inside of an assembled horn.
Thanks, Terry
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Author: Mark Charette
Date: 2001-02-03 21:03
Terry, the register on conical instruments is set to use the even harmonics, not the odd. While you can get the 12th by carefully overblowing, most people will use the regular fingerings. A clarinet can't blow an octave with the register vent, ever.
The longer the tube, the more problematical the location of the register vent. On bass clarinets there is very often a linkage to open a different register vent.
There's a step in there, but it's small and may not have a sharp shoulder.
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Author: Terry Horlick
Date: 2001-02-03 21:11
<font size="3">Mark,<small>
Thanks again, I will have to look for that stem a little more critically. Where is it located, at the middle joint?
</small>Terry</font>
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Author: Ken Shaw
Date: 2001-02-03 21:56
Terry -
The "polycylindrical" part is in the upper joint. The diameter of the bore steps down above the register vent and again below the vent. It expands between the index and middle finger holes. The differences are tiny -- a few thousandths of an inch -- and they are not visible to the naked eye, since the transitions are blended into one another. The lower joint is cylindrical until somewhere between the middle and ring finger holes and then becomes conical.
The upper 2/3 of the bore is sufficiently cylindrical that the entire bore acts as a closed-end tube (since the reed closes air-tight against the lay of the mouthpiece for more than half the time). Therefore, the pitch of the clarinet is the same as the pitch of an open pipe (say, a flute) that's twice as long. (The lowest note of the clarinet is nearly an octave below the lowest note of the flute, which is nearly the same length.) That's why, when the clarinet overblows, it does so only on alternate overtones.
Best regards.
Ken Shaw
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