I am looking for formulas used by organ builders for the 'Q' of a closed pipe. So far I have came up with Fc/Fp which makes sense, but sort of falls apart (I think) with shorter pipes. Any help appreciated.
TIA ........ hitsware
[Edited title to make it more descriptive]
As you know the Physics of Pipe Organ "Pipe Scales" is complicated.Different Builders,Different Organs,Different Buildings/Accoustics etc. all seem to vary now.Also,The 'Q' factor is different for Flue and Reed Pipes and also the different Timbres.If you type into Google "Q Pipe Organ Pipes" there are some formulas there.Otherwise,my only other suggestion is to contact as many Pipe organ Builders as you can.They may give their "Secrets" away. or also try "Pipe Chat" on the Web.Many Builders answer Tech Questions there.
Most Modern Organ Builders have Now gone away from the Audsley "The Art of Organ Building" set Pipe Scales.
The ('Q' = 'Quality Figure') for the resonance approx. Q = fc/f........
Works well with the Larger Closed pipes,but I agree,there is definately an impaired resonance with smaller pipes.
The Ranks of "Mutation" pipes....Many Modern Builders are just leavng them open.Good Luck anyway.Some Builder may be able to help.It could take up to 20 Pages here,if we got into a discussion,and many here are Orgel Players,not Builders/Tecnichians...also this 'Q' factor pertains to ALL accoustics and other Non Pipe organ 'Pipe' Matters.BTW if you get your qusestion on to 'Pipe Chat"...Seek out the Guy who has a Username "The Apprentice". He is in fact,One of the World's Leading Organ Builders
ok, I'm not at all into much of this which you are talking about... but I'm curious... so, would anyone be so kind as to explain all these designitions and what are the values representing.
Q = stored energy / lost energy
It is how selective the pipe is to it's tuned frequency
I.E. a high Q pipe has less harmonics
Fp = fundamental of pipe (primarily based on length)
Fc = cutoff frequency of pipe (lowest note the pipe can produce (primarily based on radius))
Q = Fc / Fp
>also this 'Q' factor pertains to ALL accoustics and other Non Pipe organ 'Pipe' Matters.
Yep. Thanks! ..... I'm actually using the info for ' 1/4 wave ' speakers. I figure organs have been around longer than hi-fi's so there is some good wisdom to be learned.
hmm ok... thanks... didn't do much to enhance my understanding... but hey, it's late and a little too much physics based on terms that makes little to no sence what so ever...
is it possible to play notes lower than the (harmonic)fundamental of any given pipe? - pythagoras's teachings doesn't account for any notes lower than the fundamental. - an organ must work in sort of the same way as when you blow on the bottleneck of a bottle, or is that a wrong comparison? - so how do you get any tone lower than the "fundamental" - I can see (and hear, and play) that it's possible to "overblow" it and get the above harmonics to anygiven fundamental tuning (it's the same idea as a violin (if you press down half way you get an octave compared to the full lenght of the string - or on brass instruments when changing the tension of the embouchure/lip-buzzing or indeed a flute (which is the same way as the bottle)... but how do you go the other way? (and still have an audible sound)
Trying to hook up a system that combines organ pipe and hi-fi technology :^)
http://f18.parsimony.net/forum31999/messages/66562.htm
eg.
CCC1 plus GGG1 (using a 16ft Open Pipe) will send it down to
CCCC1 (sounding a 32ft Pitch)
Really only used on Organ Pedal Division,and only successfull for the first 8 notes of that bottom octave.
Saves a Lot of Money and Space to do this.
If you have a Synth....Try it.!!!! Only use one tone...at 16ft....hold bottom C & bottom G (together) and within a split second,it will go down to 32ft pitch....then try bottom D and bottom A... etc etc etc. AND believe it or not...it is 'audible'.I agree,it's late and this physics get a bit crazy at this hour,but try that little trick above,and you will see it is possible.If you take a pipe at 32ft pitch and do the same (trying to produce an accoustic 64ft pitch)
it is more of a feeling of the sound than an actual audible one.The secret is using the 5th interval above in combination with the fundemental,THAT will take you the 'other way'
Quote:P.S. If you press the link Skandinavisk Orgelcentrum,or http://www.orgel.dk/ as in Frederik's first post you can download a few mp3's and hear the results.
They May help there.There is a "Full Explanation" of it on that link,however I am sure the Owner there would be pleased to help if you contact him.
I am really only "the apprentice" lol. at Pipe Chat.!!!!!
EDIT.
BTW. Where I live I am involved in this field..with an Organ Company..The 'Q' factor has to come out of it MOST TIMES.!!!!!!. It is a game of "trial & error".It also,as you know depends on the quality of your speakers.(can be frustrating at times..we all know the different levels & harmonics (High) that will break a Glass.There are also many (Low) harmonics that will rattle a window or something)(The Sydney Town Hall Pipe Organ has the Bottom 64ft Octave blocked off, as the vibrations would shake the foundations 'dangerously'.)(Another Organ I work with has an annoying 16ft Pedal DDD1...It rattles everything.)(All mutation stop voicing has to be carefully worked out with the Building accoustics - some work/some don't,especially the shorter pipes....some require more than one speaker etc.and different levels of 'air columns'.)BUT the expert in this field,is at the link I have given above....Will get back to you with Further Reading Matter.
Aug.Laukhuff in Germany did have all the Pipe Scales listed in their catalogue..(Old & New Scales).Again,they are also very approachable for Questions of this nature.
ahh... - that makes perfect sence now... after having slept for som 8 hours since 5 am...
Thanks Again. Here's my conundrum:
Please correct any errors of formulas.
For a closed pipe (c = speed of sound)
Fp = c / ( 4 * ( length + ( .6 * radius )))
Fc = c / ( 2pi * radius )
With a pipe of 0 length (flat baffle) you get a Q of ~ .38
???????? Should be 0 I would think........
Let's try this one:
When pure tones (sine waves) are sounded together, they combine to produce two additional tones whose frequencies are the sum and difference of the two original tones. For example, if the original frequencies are 32hz and 48hz, the resultant frequencies will be 80hz and 16 hz. While this effect occurs at all frequencies, it is most effective to the human ear at low frequencies. (This same acoustical principle is used by celestes to produce a different effect.)
These stops use this acoustical effect to produce tones in the 32' and 64' octaves, using smaller (and thus less costly) pipes than would normally be necessary. One of these stops, labeled as 32' or 64' pitch, is comprised of two ranks which sound an octave and a twelfth above the desired pitch (that is, at the 1st & 2nd harmonics). For a 32' stop, the two ranks are 16' and 10-2/3'; for a 64' stop, the two ranks are 32' and 21-1/3'.
In many cases both pitches are taken from the same rank of pipes, a fifth apart, as a further cost-saving measure. Because 5ths in the equal-tempered scale are not perfect fifths, the resultant tones will not be quite in tune, but it works because the human ear does not hear such low tones with enough accuracy to tell the difference.
The name Gravissima is typically only used for a 64' stop.
N.B. There are exactly two true 64' stops in existence. One is the Diaphone Profundo at Atlantic City; the other is a Contra Trombone at the Sydney Town Hall.
Tonal Attributes
In order to be effective, the pipes should be large scale flues, either open or stopped. Bourdons and Diapasons are most often used; reeds are almost never used.
Usage
This stop is a replacement for a true 32' or 64' stop. It is not as effective as a true stop, but is often the only economical way to obtain 32' tone in a modest instrument. It is almost invariably found in the pedal.
Variants
A single 5th sounding stop at 10-2/3' or 21-1/3' pitch is often provided to achieve the same effect. This has the advantage that it can be combined with a variety of octave sounding stops. See Grossquintenbass.
Examples
32' examples are fairly common. 64' examples are rare, Julian Rhodes keeps a compilation by David Willey that lists about 40 examples (see Bibliography below). A few examples are listed here.
Gravissima 64'; Woolsey Hall, Yale University, New Haven CT; Hutchings-Votey Organ Company.
Gravissima 64'; Worcester Cathedral, Worcester, England; Hope-Jones.
Gravissima 64'; Liverpool Cathedral, Liverpool England; Willis.
Gravissima 64'; Bremen Cathedral, Bremen, Germany (destroyed?); J. F. Schulze.
_____________________________________end.
Now corno,at this hour in the morning I had to resort to going to The Bible for Organ Builders & Organists. lol.
http://www.organstops.org/ Click Middle link on page & all
sorts of things appear about pipes and also somewhere in there is all about this 'Q' factor (I think).
hehefor more use of the Brass Section in new works.etc.
So I have to fully agree with Pythagoras (let's not disturb him now) and also in answer to your question,NO.!!!! there is no real way that you can produce an 'audible' & 'true' sound BELOW its fundamental.(without cheating).Also,your 'bottleneck' comparison is a very spot on way of understanding the upper harmonics. etc.
Many have tried. Haskell was one who tried in the early 1900's of taking a pipe and inserting another pipe to try and lower pitch,without lengthening the pipe (was also tried in the early 17th cent in spanish organs)."Haskelling" a pipe is sometimes still used now,but not very good results.
I am sure Haskell and other methods are in The Bible at above link.The mutation section is interesting,in relation to the higher notes.....this is where,I think, the 'Q' factor is explained better.
Time for a coffee break. Jamie
rambling,but did not see your post until after. wooooosh this stuff does get interesting & what forums are all about.
have linked/hooked up with that url....also read many of the tech ?????? there as well..Hi-Fi = Hi-Tech lol
http://www.quarter-wave.com/
This guy takes it to the max but his program runs in 'Mathcad' which is clunky on my machine......
Full acknowledgement and Thanks is given to:
The Encyclopedia of Organ Stops: copyright © 1999-2003 by Edward L. Stauff.
Permission is granted to use small excerpts from this work for educational and/or non-profit purposes, as long as due credit is given to the author.
Copying in whole, or in large excerpts, via any medium, is expressly forbidden without written permission from the author, with the exception of quoted material in the public domain, or quoted material covered by another copyright.
Any for-profit use is likewise forbidden without written permission from the author.
____________________________________
This is for using The section on Resulant Bass 32' in previous post from the URL link given there.
Jamie.
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