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Since most of my organ playing has been on electronic or digital organs, I have never really understood the "inches of wind pressure" thing. I see that some organs (or certain ranks) are voiced at 3 or 4 inches, while others are voiced at 6 to 8 inches or even higher. Does the wind pressure help determine the volume (loudness) of the pipe?And how does that relate to the "scaling" of a rank. It would seem that if a pipe were blown by higher pressure it would just result in the fundamental being overblown resulting in thepipe sounding only the overtones. Can someone please explain this in a concise intelligable way? Or refer me to a website that would explain it. Thanks for your help.
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Re: Inches of Wind Pressure - What is it all about?
Wind pressure is part of the design of the organ and bears relation to scaling of the pipes. That's why the pipes are voiced to the pressure used in the organ.
You are correct that if you take a pipe voiced on 3" and put it on 6" that you will simply overblow it. But part of the voicing procedure is to make the pipe speak correctly on the pressure used. So there is a relation between height of the mouth and width of the slit and the wind pressure.
The relation between pressure and loudness if less. (there are old italian organs that use 2" and fill a huge cathedral with sound) Loudness is more a function of how much volume of air that is put in resonance. So organs with low pressure will use plenty of air to sound loud, organs with lots of pressure will use less air for the same loudness. This has more implications for the bellows and chest design. Intonation also has some bearing on loudness.
A lot of work on this has been done by a chap called Ising: http://mmd.foxtail.com/Tech/isint.html
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Re: Inches of Wind Pressure - What is it all about?
Well said, Havoc!
Allow me to add for the benefit of the unititiated that scaling also impacts loudness. As you mentioned, loudness relates to the volume of air that is put in resonance. Our former 16-rank organ at church (now integrated into our rebuilt III/72 Schantz) was on 2-1/2 to 3 inches. But the pipes were large scale and had open-toed voicing. The principals could actually sound rather agressive at times. The organ was somewhat 'overvoiced' in an attempt to fill the large church with a 16-rank organ. These pipes havebeen revoiced on slightly higher pressure, but with the toes now closed and they sound much nicer.
As Livia Augusta said to Martina: "It's wind."
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Re: Inches of Wind Pressure - What is it all about?
If you close the toes but make the pressure higher, then in fact (maybe) you don't change anything in the speaking parts of the pipe!
Let me explain, but some phisycs will creep into this. Lets make an analogue to electricity since more people are used to that as to pneumatics. Making the pressure higher is the same as making the voltage higher. A large opening is a low resistance and a small opening is a high resistance. So if you close the toes, you make the resistance to airflow higher. But if at the same time you make the pressure higher, the same rate of air (measured in mass per time unit) will be about equal. Like in an electrical circuit when raising the voltage but at the same time raising the resistance will get you the same current. Since after the closed toe you have a "void" (= the air space in the foot of the pipe) this can be equalled to a capacitor in electricity. So you have a lower air pressure in the pipe foot. Maybe about the same as you would have had on the old pressure and an open foot.
So maybe you raised the pressure, but by closing the foot, you didn't change the mass of air that goes through the pipe at a given time. So volume (as expressed in loudness) is about equal.
Now, this is only true if they didn't change anything else! And this is anly true for the sound level. It doesn't tell you anything about how it sounds (the colour of the sound). Maybe it is just as loud but a "nicer" sound? This is the artwork of the voicer.
Voicing is a very complex work. There are so many parameters that simplifying it to pressure and toe openings is too much. Some of the parameters are:
- wind pressure
- toe opening
- height of the cut
- mouth wide in relation to circumference
- lenght to surface
- depth of the mouth
- form of the foot
- relation of the lip to the slit
- form of the pipe (cilindrical, closing to the top, widen to the top, open, closed...)
- form of the mouth (clean, with barbs, with nicks,...)
and these are only the most important ones and they are all related to one another! Changing one of them means you have to change others to get the same sound back (or not if that is what you want).
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Re: Inches of Wind Pressure - What is it all about?
Another way of looking at wind pressure is to examine the intended result of designing an organ for a particular pressure. A quick summary is:
1. Low pressure 2 to 3" is the neo-baroque ideal. The pipes will have a "breathy" sound with a bit of windiness. It is more difficult to achieve uniform sound across the entire range so as a scale is played on a single rank, there will appear irregularities in the volume and sound quality. A larger ensemble heard in a large space with some distance will tend to cover up these imperfections. Reeds are difficult to keep in regulation and in tune with low pressures. To get quick speech, with low pressure, the pipes will usually have an initial inharmonic transient (chiff).
2. High pressure instruments are ones with 7 to 10" chest pressure. These instruments are characterized by smooth even voicing, reeds more easily kept in tune (except for short resonator reeds such as vox humana), and lack of the windiness characteristic of low pressure voicing. These organs come from the "romantic or theatre organ" era and are considered "evil" by the neo-baroque enthusiast. E.M. Skinner organs fall into this category.
3. Medium pressures. Some organs will have the flues on a lower pressure and the reeds at higher pressure to get the best of both worlds. The design of organs in the French (Cavaille-Coll) and English (Father Willis) eras and some new instruments use this compromise design. These organs represent probably the peak of the organ builders art. Modern builders are beginning to re-discover the beautiful sound that these instruments provide. Chiff is not necessary in this design and is only supplied if the organist desires to simulate a baroque type sound.
My picture indicates my preference in organ wind pressure design (Wurlitzer Style D Theatre Organ). My instrument is at 10" wind except for the vox humana at 6". The volume level is high so the pipes must be enclosed in a chamber with shutters to control the sound level to achieve soft effects. Pipe speech is very quick without chiff.
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Re: Inches of Wind Pressure - What is it all about?
I seem to recall having heard about a theater organ that put some of its reeds on 60" of wind. I think it was an outdoor instrument.
DavidComment
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Re: Inches of Wind Pressure - What is it all about?
probably talking about the Roosevelt Park wurlitzer. VERY VERY loud instrument. Most of the ranks are on 25" and some are on 50"!!
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Re: Inches of Wind Pressure - What is it all about?
Just out of curiosity, what kind of pressure would we be talking about for Atlantic City and/or Wanamaker?
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Re: Inches of Wind Pressure - What is it all about?
Here is Wanamaker Organ's pressures
THE MAIN PEDAL DIVISION is unexpressive. It has forty-four stops and wind pressures of five to twenty-five inches.
THE CHOIR is on five inches of wind pressure.
THE GREAT DIVISION is on wind pressures of five to sixteen inches, and consists of unenclosed stops as well as a section enclosed with the Choir division.
IN TWO EXPRESSION CHAMBERS, THE SWELL is on wind pressures of five to twenty-two and a half inches
THE ENTIRE SOLO DIVISION is under expression, on a wind pressure of fifteen inches
THE ETHEREAL ORGAN a wind pressure of twenty-five inches.
THE STRING ORGAN is entirely expressive, has eighty-seven manual stops and a wind pressure of fifteen to twenty-seven inches
THE ORCHESTRAL has pressures of fifteen and twenty inches
THE ECHO DIVISION a wind pressure of five inches.
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Re: Inches of Wind Pressure - What is it all about?
The wind pressure discussion has been a very good one, but no one has ever said that organ pressure is measured in inches of what???
Have any of the persons in the discussion seen or used the measuring device?
Just wondering - I know, I have, have you?
Bill
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Re: Inches of Wind Pressure - What is it all about?
That's inches of water in a column. You can make a pressure gauge yourself, using flexible clear hose with inches marked inink. Before measuringyou make an "s" shape (like thedrainpipe under a sink) so as to keep the water from flowing down into the chest (a very very bad thing)!
Actually, this procedure is risky to the point where I don't recommend it at all. As they say, "don't try this at home"! [;)]
I have a exceedingly nice mechanical windpressure gauge made by Laukhuff. That is much more practical.Comment
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Re: Inches of Wind Pressure - What is it all about?
The Orgelbau Klais workers used a manometer of water to measure the wind pressures. Of course, it was a device specifically constructed for that purpose and had features to prevent getting water in the wind chest. (Also, they do it all the time and are quite skilled professionals....)
For anyone who is not conversant with different ways to measure pressure, one atmosphere (atm) is equivalent to 760mm (approx. 30 inches) of mercury (Hg) in a manometer and to 33 feet (approximately400 inches) of water, and measures 14.7 pounds/square inch (psi). Wind pressure of 50" of water is very high--many organ stops are only working with 2 or 3 inches--and that high pressure is stillonly about 1/8 of an atmosphere (about 2psi). The pressures at which organ pipesoperateare easily within the capability of human lungs to supply, and voicers (the people who tune and adjust the tones) frequently just blow into the pipes to test their sounds during the preliminary stages. (Fine tuning is done with the pipes in place in their wind chests.)
DavidComment
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Re: Inches of Wind Pressure - What is it all about?
You might be able to build the pressure, but you won't have the capacity to provide air for a 32'. And blowing into a pipe is bad for the pipe. Your breath contains too much humidity that condenses in the pipe. Specialy reeds are suffering from that. Other point is that your breath heats the pipe and detunes it from that. So never blow in a pipe unless it is intented for the scrapheap.The pressures at which organ pipes operate are easily within the capability of human lungs to supply, and voicers (the people who tune and adjust the tones) frequently just blow into the pipes to test their sounds during the preliminary stages. (Fine tuning is done with the pipes in place in their wind chests.)
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Re: Inches of Wind Pressure - What is it all about?
Right, Havoc. I never blow into a reed pipe. I only blow into a flue pipe when doing on the spot corrective voicing, such aswhen the languid has fallen. That tells me if the pipe is on speech or not; if it is quick or slow, etc. Of course the pipe needs to cool before it can be tuned.
Also, most pipes contain lead - you don't want to ingest even a tiny bit of that. If I need to blow into a pipe, I've been trained to use my hand as a sort of 'bridge' between the pipe and the mouth.Comment
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Re: Inches of Wind Pressure - What is it all about?
[quote user="solotibiaclausa"]probably talking about the Roosevelt Park wurlitzer. VERY VERY loud instrument. Most of the ranks are on 25" and some are on 50"!!
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That's the one! I lived in Torrance, California for 2 years and heard that organ on several occasions--you are right, it is VERY loud! I found this link on the web: http://members.aol.com/theorganst/Page1.html. The Specification gives the wind values for each stop.
DavidComment
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