Klarinet Archive - Posting 000128.txt from 2009/09
From: "Peter Gentry" <peter.gentry@-----.uk>
Subj: RE: [kl] Antique clarinet length determines diapason?
Date: Mon, 28 Sep 2009 05:46:31 -0400
The acoustic properties of wind instruments whilst at one level amenable to
simple mathematical relations are at the accurate musical level elusive and
intractable. However I find the use of obscure and ill defined musical terms
such as "diapason" more commonly associated with church organs serves only
to further obscure the issue.
regards
Peter Gentry
-----Original Message-----
From: Doug Potter [mailto:doug@-----.net]
Sent: 27 September 2009 08:19
To: klarinet@-----.org
Subject: RE: [kl] Antique clarinet length determines diapason?
In principle, the length represents a quarter wavelength of the lowest note
- or 3/4 of the lowest note with the register key pressed. This would
include part of the length of the cavity in the mouthpiece. If you divide
the speed of sound by the wavelength (4 times the length), you get the
approximate frequency. Alas, there are end effects to take into account -
so the number is only approximate.
Conveniently on a Bb clarinet, the lowest note in the upper register (B) is
concert A 440
Working down by a twelfth gives about 147 Hz for concert D (E transposed).
The length of my Bb clarinet is 25" - 23 1/2 in the body and about 1 1/2 in
the mouthpiece. I have to make a correction of about 8% less in the length
to get it to match these frequencies:
Body 23.5 inches
mpiece 1.5
total length 25 inches
correction 0.923
corrected length 23.075 inches
total length 0.586 meters
sound speed at 20 deg C 344 m/s
frequency of low E (transposed) 146.73 Hz
frequency of mid B (transposed) 440.19 Hz
Perhaps some of that 8% ought to be in the speed of sound - which is
temperature dependent.
My A clarinet is about 25" in the body - and that gives about 138.4 Hz for
the lowest note. What I expect for that concert Db is 137.5 - fairly close.
If we plug in your 20" we get about 170.6 Hz for the lowest note - closest
to F (174.6) - but also near E (164.8). If it's E, the instrument is in C
(more likely). If it's F, it's in C# (less likely as far as I know).
So I think the length can perhaps give you the key, but it's unlikely to be
exact enough to give you the diapason (a new word for me, thanks for
defining it).
Doug
http://ConicWave.net
-----Original Message-----
From: Simon Aldrich [mailto:simonaldrich@-----.ca]
Sent: Sunday, September 27, 2009 10:46 AM
To: klarinet@-----.org
Subject: [kl] Antique clarinet length determines diapason?
In the murky world of determining an antique clarinet's diapason
(A430, A435, etc) is length of the instrument any sort of indication
of its possible diapason?
Specifically I am thinking of an 1860 boxwood Lecomte 13-key clarinet
of 20 inches (without mouthpiece).
Many sellers don't know the diapason (let alone the key) of the
clarinet they are selling.
In such a situation, is the length helpful in determining
characteristics of the instrument such as its key and possibly diapason?
------------------------------------------------------------
Simon Aldrich
Clarinet Faculty - McGill University
Principal Clarinet - Orchestre Metropolitain de Montreal
Principal Clarinet - Orchestre de l'Opera de Montreal
Artistic Director - Jeffery Summer Concerts
Clarinet - Nouvel Ensemble Moderne
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