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Thread: A Not So Elementary Question:

  1. #1
    ppp Pianississmo HiDesertHal's Avatar
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    A Not So Elementary Question:

    Hello,

    I'm an 81-year-old retired Boeing Lab Test Engineer, and I'm quite familiar with Aircraft Electrical and Mechanical systems.

    However, I'm not that familar with Pneumatic systems!

    For 55 years, I've wanted to acquire a Reed organ, having owned several Electronic organs, my last one being a Conn 650 Theatre Organ (with a rank of Speaker pipes), and now that I'm in the market for a Reed Organ, I'm beginning to study how they work.

    But the book I've bought: "The American Reed Organ" does not answer one elementary question I have:

    Why are Reed Organs powered with Vacuum instead of Pressure?

    I've always thought that you pump the bellows to pressurize the Reservoir, so that air will blow over the reeds when keys are pressed.

    Is there some reason why its preferable to let atmospheric pressure produce the wind against a vacuum instead of positive pressure?

    Thanks,
    Hal
    Last edited by HiDesertHal; 09-09-2017 at 08:59 PM.

  2. #2
    pp Pianissimo OneWatt's Avatar
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    Quote Originally Posted by HiDesertHal View Post
    Hello,

    I'm an 81-year-old retired Boeing Lab Test Engineer, and I'm quite familiar with Aircraft Electrical and Mechanical systems.

    However, I'm not that familar with Pneumatic systems!

    For 55 years, I've wanted to acquire a Reed organ, having owned several Electronic organs, my last one being a Conn 650 Theatre Organ (with a rank of Speaker pipes), and now that I'm in the market fo a Reed Organ, I'm beginning to study how they work.

    But the book I've bought: "The American Reed Organ" does not answer one elementary question I have:

    Why are Reed Organs powered with Vacuum instead of Pressure?

    I've always thought that you pump the bellows to pressurize the Reservoir, so that air will blow over the reeds when keys are pressed.

    Is there some reason why its preferable to let atmospheric pressure produce the wind against a vacuum instead of positive pressure?

    Thanks,
    Hal
    Hal - A fascinating question, which piqued my curiosity...

    From this linked page on Wikipedia https://en.wikipedia.org/wiki/Pump_organ I learned the following:

    "As reed organs with pressure bellows were more difficult to produce and therefore more expensive, North American and British reed organs and melodeons generally use suction bellows and operate on vacuum."

    Apparently, it was about construction costs, at least in the early days.

    Regards - OneWatt

  3. #3
    ff Fortissimo SubBase's Avatar
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    It's a manufacturer's preference (or is it cultural?) because the reed can't tell the difference.
    Some of the best pressure instruments try to sound round-toned like suction ones, and vice-versa, some of the costliest suction instruments had additional very reedy-voiced sounds.
    The most prolific US pressure reed organ builder was Vocalion, which was voiced and modulated to sound as close to a pipe organ as possible. (see my avatar pic)
    Casey

  4. #4
    ff Fortissimo Organfella's Avatar
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    Interesting question. I own both pressure and suction models and to my ear the major difference between the two sound-wise is volume. I find on the one working pressure model I have it seems to be somewhat more noisy than the suction models, kind of blowing the sound outwards rather than sucking it in.

    It is apparent though that pressure systems generally require more care in achieving proper sealing and therefore "better" materials are used, hence the reference to cost. As Casey remarked there might be a culture element in the whole thing. We have come to know our American friends to often want to change everything....

    Nico
    "Don't make war, make music!" Hammonds, Lowreys, Yamaha's, Gulbransens, Baldwin, Technics, Johannus. Reed organs. Details on request...

  5. #5
    ppp Pianississmo telegraphroad's Avatar
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    I have no personal knowledge or experience of pump organs so I'm just a fellow engineer speculating here but the question of sealing could well be relevant. A small leak from a crack or split in a part of the air chamber or bellows would be more likely to close up during operation with a vacuum driven system. A pressure driven system would cause the leak to open up and therefore leak more. Also, noise from a leak out would be likely to propagate more as the perturbed air will be travelling outwards from the leak rather than into the cavity. However, if vacuum systems are cheaper to produce and/or maintain then that would be the overriding reason to me.

  6. #6
    pp Pianissimo Rodney's Avatar
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    As long as there is wind movement, the reed will move, it cut the air flow on and off again, and speak through the air movement if it is set up properly – it doesn’t matter which direction of air is moving. Think of it as whistling – it can be done by either blowing or sucking air.

    Most pressure harmoniums will have wadding for sealing the air between stops/wind chest, leather gussets and carefully cut wood ribs for the feeders and reservoir, and generally a lot more to it than what you would find in a suction reed organ. They are more time consuming to manufacture, setup and tune - plus import duties from the European manufacturers did not make them an easy sell in the USA.

    Most suction reed organs can just be slapped together with inexpensive rubber cloth and cardboard ribs (or no ribs at all!) and sealed up with strips of leather or paper as gaskets. Tuning can be done while the reed is speaking (without lifting the chest each time), which made mass production in the USA and Canada rather easy and cheap.
    To play a reed organ or harmonium, it helps to disconnect your feet from your brain and connect them to your emotions.
    Most of all, be creative, make music and have fun...


    Website: http://www.rodneyjantzi.com/

  7. #7
    pp Pianissimo OneWatt's Avatar
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    Thank you as I've learned a bit more reading these additional replies.
    Notwithstanding my initial assumption, it's now clear that vacuums do not suck.

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