What does heavier valve caps do ?

Discussion in 'Trumpet Discussion' started by Laursen, Feb 18, 2010.

  1. B15M

    B15M Forte User

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    It's been a long time since I read about them. It was very interesting reading. (on TH) The guy noticed that the Chicago symphony horns had thicker patches on them. The question is, did these get put on to make the trumpet play better or to fix something.

    Here is a link to what I found when I googled it
    Home Page
     
  2. rowuk

    rowuk Moderator Staff Member

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    That the peaks (slots) on my Monette Prana3 were of higher amplitude with the Monette bottom caps than without and that 4th space E and Eb were flatter with the caps than without (the E and Eb are too sharp normally).

    The amplitude of the peaks on my Bach C did not change but the 4th space E and Eb as well as the 4th line D got even flatter. The 3rd space C and top of staff G got sharper.

    When I say flatter or sharper, that means that the frequency where the peak of the peaks are. The peaks on the trumpet are not symmetrical so the "average" center does not necessarily correspond to the peak.

    Go to any DIY loudspeaker construction site. They have easy ways to measure loudspeaker impedance with just an ohmmeter. A computer generates the tones and you can write down the frequencies of the impedance "peaks". Gluing a headphone driver to a mouthpiece with hot glue makes it easy to try different mouthpieces with no permanent damage.

    A bit more professional is the software Arta and Limpa, Clio or Mlssa. I use Arta and Limpa.

    This of course only shows what the trumpet wants to do. Our chops can bend the notes quite a bit, which also changes the tone - I believe this is what some players actually experience.
     
  3. gzent

    gzent Fortissimo User

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    Interesting, what the horn wants to do, versus what the chops/player does.

    I don't recall who said it, might have been Dave M., but someone said that his trumpets take some time to get used to because they don't have the intonation issues of "normal" horns, so when a player who is used to lipping a note up or down picks up a new horn they might be lipping a note out of tune that doesn't need to be lipped, so to speak.

    What signal did you drive your mouthpiece with? I can see how the results would be extremely sensitive to the driving signal.
     
  4. rowuk

    rowuk Moderator Staff Member

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    The waveform is actually not critical. A sine wave gave the easiest to read impedance measurements. Our lips actually pulse non linearly so a sawtooth wave probably would be a good technical choice - plenty of odd overtones. What comes out of the front sounds amazingly like - a trumpet. No fast air, no abs, no aperature.

    That Limpa system that I mentioned has its own wave generator that works with most computers. I used a USB DAC/ADC - an MAudio Fasttrack pro and one channel of a 2x 60W amplifier that I designed and built myself.
     

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