Compression?

Discussion in 'Trumpet Discussion' started by 9horn, Jan 28, 2010.

  1. Voltrane

    Voltrane Pianissimo User

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    Sep 13, 2006
    Paris
    Hello,

    VB wrote: <Third, maybe fourth hand info (from a french horn player, no less!), but one famous repair tech said that at the customer's request he fixed the compression on some vintage old french horns (slides and valves) and they played much worse than before. He speculated that they were sort of designed with poor compression in mind and would still play fine.>.
    But is not the "heavy oil test" the answer? I have an old London Besson with worn and leaky valves, with a bad low register. I oiled it with arachid oil and the sound was great. So why should a valve replating not achieve the same result? To sum up, in case of doubt, I would make the oil test and if the result is good, have the valve rebuilt.
    Regards.
    Marc
     
  2. oldlou

    oldlou Forte User

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    You have hit the nail perfectly on its head. Heavy valve oil is just a test to determine if the horn is worthy of a $350-$450 valve rebuild.


    OLDLOU>>
     
  3. rowuk

    rowuk Moderator Staff Member

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    To be honest, I think that compression is overrated. Trumpets are actually playable because they do NOT follow horn theory exactly, because they have imperfections in the bore (like gap), because of the weight distribution affecting resonance and the unpredictable behaviour of mouthpieces.

    There are reports of "night and day" resulting from thousandths of an inch difference in leadpipe or mouthpiece size, valve oil manufacture, dents, lacquer/plating.

    I have a Holton Clarke model cornet from 1911 that has REALLY leaky valves, yet all of the Arban and Clarke solos are playable with ease.

    I am not saying that compression is unimportant, I would place it way behind your blood pressure on stage in my scale of things.

    I don't think that it has a sound.
     
  4. simso

    simso Pianissimo User

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    Jul 1, 2009
    Australia, Perth
    Compression is really irrelevant as far as testing an instrument, its used by a lot of people to say Oh yeh your instruments in great shape or poor.

    The fact is it has nothing to do with it.

    I pressure test instruments for leaks on solders slides and keys, I do leak down checks on clean dry assembled valves.

    In the perfect world, a trumpet or valved instrument with no oil on valves will have less than 0.002" side play at 3 locations in all directions down the valve chamber measured at the touch point, in a professional instrument this should be less than 0.001", however Ive seen instruments play with as much as 0.004" side play with no problmes, simply increase the viscocity of the oil in use.

    The biggest issue with side play also is not really to do with lost compression as well, its more to do with valves sticking during there travel
     
    Last edited: Jan 30, 2010
  5. missmybaby

    missmybaby Pianissimo User

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    Sep 27, 2009
    Detroit Metro
    My Conn 80A has worn valves, and I really like the way it slots loosely. I can tell I am wasting some energy in blow-by, but the sound is so nice. I have a King Master that has really worn valves, it's miserable and needs a valve-job badly. I could put the face time on the horn and maybe learn to live with it (using heavy oil), but it's just too much effort. Obviously the horn was a player at one point in time, so when I have the spare cash, I will invest in the valve replating. So, some loss in compression is ok, but I believe there is a point of no return.

    On a side note...
    Wow, talk about N+1, lol. You're the official posterboy, now, CBK! You should neatly lay them out in the yard, hire an aerial photographer and post the picture of your arsenal sometime for all to behold.
    :-)
     
  6. aptrpt12

    aptrpt12 New Friend

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    Boston/Providence
    How does it sound is more like how does it play? I am not a technician, but I brought my horn in to have it repaired by Osmun Brass. They checked the compression at that time and I found that the 2nd valve was at 65%, the first at 75% and the 3rd at 95%. Nothing had been done to the valves since I bought it in '67, just a lot of practice and playing. Most of my playing has been solo and symphony work and what I was finding is certain notes were cracking on me when I would play the heavily accented. I started to play the pieces on another horn and it would not happen. For me that was the most telling problem, and then it was intonation. For a long time I thought it was me and started practicing a lot more. I guess some was me...the practice did me some good, but it WAS the compression.
     
  7. ComeBackKid

    ComeBackKid Fortissimo User

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    Interesting - just about an exact inverse ratio to the frequency of use of the valves, but this is the first time I have seen actual numbers put on it.

    Just curiosity question. Did Osmun fix the #1 & #2 and then did that correct your cracking problem immediately?

    Yeah, my yard isn't big enough. I'll need to rent the soccer field across the street. The biggest problem is that if I drag them all out at once and my wife sees them all...well, let's not even go there.:shhh:
     
  8. Wondra

    Wondra Pianissimo User

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    Mar 29, 2007
    Absolute, air tight compression is actually overkill. In the past I've wasted money on valve jobs because of my previous belief that air tight was important.

    Consider this - your air will follow the path of least resistance as it moves through the horn. As your air moves through the valves, there are some pretty big openings that the air will move through. Here's the key point - it takes a whole lot of air pressure to over blow the openings to the extent that air starts to move around the outer body of the piston.

    The way to really determine whether or not your horn needs a valve rebuild is to have a tech do a compression test. I have a horn that seemed to leak air, based on the usual "blow in the leadpipe, block the slide opening method". After getting a compression test done, I found that there was no way I could (or would want to) blow hard enough for this suspected leakage to be a problem. The test saved me $400.

    Sometimes we (and especially me) can go overboard in the pursuit of perfect.
     
  9. veery715

    veery715 Utimate User

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    and laying them out in the yard has its attendant risks, too. Oh, the horns... OK.
     
  10. 9horn

    9horn Pianissimo User

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    Feb 25, 2009
    New York
    I like your point abount "how does it play" being the question, but that brings me back to examples like was made with Rafael Mendez liking the way it played when in fact it had bad compression. The notes didn't "crack" for Mendez? It seems more to be, how as an individual player you master the blow on your own horn. :play:
     

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