Saxophone Forum


by MartinMods
(63 posts)
5 years ago

My Reed Won't Stay Closed.

Good thing too right? Here's a question for the Wizards. When the energy wave arrives back at the mouthpiece, after making 2 windsprints the length of the sounding tube, it is a rarefaction and causes the reed to close, With the reed now closed, the tube is a resonating chamber. THe wave heads down the tube again on it's 3rd lap, still a rarefaction, but when it arrives at what the acoustical system "sees" as the body tube entrance, or the point of truncation, the difference in acoustical impedance causes a partial reflection of the wave, which goes back to the mouthpiece as a pressure wave and causes the reed to open. So, the amount of time the reed is closed during each cycle is determined by the resonance freuency of the cone's truncation. Some people say that the mouthpiece is the truncation while others (Benade) claim that the mouthpiece + neck are the truncation. My question is: What does the acoustical system "see" as the truncation, or, where is this point where the change in acoustical impedance causes the partial pressure wave reflection which opens the reed? Depending upon the answers, the next question may be about the significance of the 10M neck bend.

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  1. by kelsey
    (782 posts)

    5 years ago

    Re: My Reed Won't Stay Closed.

    Martin Martin Martin ! Are we supposed to be impressed with your endless amount of useless information, and does it really matter to anyone what the acoustical system sees?(if this is a joke, very creative of you Martin) Saxophones are to make music with, not for endless dribble about my reed won't stay closed.
    Barry Kelsey

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    1. by MartinMods
      (63 posts)

      5 years ago

      Re: My Reed Won't Stay Closed.

      You may think it dribble, but it doesn't change the fact that the less the reed stays closed, the more acoustical pressure driving the sound. This is why a soprano saxophone is 14db louder than a clarinet. If you know what the acoustical system sees, then you can manipulate it to your advantage and make better music. I would think that getting more sound out of the horn would be of interest to all sax players. And my name is not Martin.

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      1. by Mr.J
        (1 post)

        5 years ago

        Re: My Reed Won't Stay Closed.

        oh dear god MM, I see you are already making good friends on here!

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        1. by MartinMods
          (63 posts)

          5 years ago

          Re: My Reed Won't Stay Closed.

          Lol.... While I have met many capable musicians who could care less about the finer technical aspects of their instrument and how it works, I have never known anyone who's talent, musicianship, or musical taste has suffered as a reslut of learning something new in that regard - quite the contrary actually. It's a serious queston. I don't know the answer. I emailed Dr Joe Wolfe at UNSW about it. I'll post a summation of his answer here when he replies.

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        2. by kelsey
          (782 posts)

          5 years ago

          Re: My Reed Won't Stay Closed.

          Sorry Martin, it takes all kinds!..............Kelsey
          Barry Kelsey

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        3. by cuber
          (653 posts)

          5 years ago

          Re: My Reed Won't Stay Closed.

          wow.... that entire post went right over my head. all i know is that i blow and sound comes out...

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        4. by kelsey
          (782 posts)

          5 years ago

          Re: My Reed Won't Stay Closed.

          Cuber, you are not the Lone Arranger!...Kelsey
          Barry Kelsey

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        5. by MartinMods
          (63 posts)

          5 years ago

          Re: My Reed Won't Stay Closed.

          ..but you can tell that a soprano sax is much louder than a clarinet, even though they are the same size. The reed on a clarinet is closed against the mouthpiece 50% of the time you are blowing on it. The reed on a saxophone is closed only around 25% of the time (actually it varies, depending on which register/note you are playing.) because this little reflected wave goes back up to the mouthpiece and makes it open. That's why you can put more air through a saxophone.

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        6. by cuber
          (653 posts)

          5 years ago

          Re: My Reed Won't Stay Closed.

          I dont play the clarinet, so i really cant comment with any knowledge on the comparison of the two, but some questions do come to mind. Wouldnt the size of the opening on the mouthpiece have more impact on the time the reed is closed than the register you are playing in? but would size affect "loudness" anyway? i dont think acoustics work that way. ... had a question, just forgot it... kelsey- you dont know that.

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        7. by MartinMods
          (63 posts)

          5 years ago

          Re: My Reed Won't Stay Closed.

          From your question, i see that there isn't too much that goes over your head. From what I understand, this reed behavior occurs after a certain dynamic level is reached - say for example at 30% maximum blowing pressure, the maximum blowing pressure being that point where the system backs up and won't get any louder. The difference between a small and a large tip opening is the amount of reed motion (amongst other things) which means volume or loudness. The point of this clipping reed behavior would still begin at say 30%, but at 30% of a much wider potential dynamic level. Dr Wolfe responded clearing up the point of truncation issue. The mouthpiece and reed volume compensate for the missing cone volume. So the neck and it's volume are not included, That means that the point of truncation is the small end of the neck, not the tenon.

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        8. by Sax Mom
          (964 posts)

          4 years ago

          Re: My Reed Won't Stay Closed.

          I'm not sure of the science of this question... it doesn't sound right to me. I believe the reed vibrates with the air that passes over/by it, and that the tension of the reed re-opens the space, rather than any need for a soundwave to travel back to do so... otherwise if you pushed the reed up to the mouthpiece with your toungue without producing any sound, it would stay there, which it doesn't...

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        9. by MartinMods
          (63 posts)

          4 years ago

          Re: My Reed Won't Stay Closed.

          It's an observation made by quite a few published acousticians, in an attempt to explain everything about the instruments we take for granted. The wave described, causes a hole in the frequency spectrum - a formant - which is to some extent responsible for the characteristic sound of saxophones.

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        10. by blackfrancis
          (396 posts)

          4 years ago

          Re: My Reed Won't Stay Closed.

          MM- it truly went over my head too, but I'm interested, especially in the 10M neck bend aspect (as I have a 10M neck). Is that a regular or underslung neck, and is there any difference?

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        11. by MartinMods
          (63 posts)

          4 years ago

          Re: My Reed Won't Stay Closed.

          Most certainly the 10m neck bend is somewhat responsible for the horn's sound. A bend in tubing acts as an enlarged and shortened tube, compared to a straight section the same diameter. Gradual bends have very little effect, however I measured the arc of the 10m bend and it is sufficient to cause the entire standing wave to shift, if only slightly, along the entire body of the horn. In this game even slight changes can have noticable effects. I plan to make some The Martin Tenor neck copies with 10m bends, to see what happens.

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