Search the Community
Showing results for tags 'pressure'.
The pendulum has swung back an I'm resuming my theoretical interest in how free reeds work and it would help me to decide on a physical model if I knew how the musical pitch varies with bellows pressure, if at all. I ask this question mainly to the makers, but also to other enthusiasts who do their own tuning and tinkering in a serious way. But please report what you are sure of. If you're not sure, that's perhaps evidence that pitch variations are very small. Ideally, it would be nice to have quantitative data, such as cents pitch change with so much change in pressure, inches or cm in water column. But even naked ear observations can be helpful, if they can be stated with confidence. It would also help in the ideal case if you could supply the magnitude of the bellows pressure along with the pitch information. What minimum and maximum values for bellows pressure do you subject your reeds to? What range of bellows pressure do you expect in all playing situations? I've read that at the lowest pressures, pitch may first decrease with increasing pressure, then might increase with pressure at the highest pressure levels. Has anyone observed this? In the near future, I hope to do my own experiments on this topic, and afterwards, I'll present the results. I think that the pressure/pitch behavior is most fundamental to the free reed, and so reliable characterization in practice would be most appreciated. Best regards, Tom www.bluesbox.biz
Wondering if anyone has a good suggestion for an air pump for tuning and playing with reeds? I saw an earlier discussion that more-or-less concluded that an old bellows was the way to go. Probably OK for tuning, but I also want to do some experiments with reeds, and a constant-flow, hands-and-feet-free system would be preferable. Ideally quiet so as not to interfere unduly with measurements and recordings. Desirable to have suck and blow available. Don't want to spend a fortune though. Any bright ideas? Good to know too what people have tried and how well they have gone. Nice to know what traps one might fall into! Terry
You may remember me talking about getting some bits together to research concertina pneumatic issues. Well, the slow boat from China has come in, and the even slower boat that is me seems to have got its act together. Here's the result: An explanation of what it it comprises is at http://www.mcgee-flutes.com/Concertina/Concertina%20pneumatics%20lab.htm An interesting little challenge that came up too.
Wondering if concertina repairers ever resort to pressure testing the seating of pads? Pad seating is critical in flutes, but it's pretty easy to do a suck test, so most flute repairers just do that. Being somewhat of a fetishist, I use a Magnahelic Flute Leakage meter to refine that test. The Magnahelic is essentially a combination of a small air pressure generator (an aquarium pump in reality), a regulator to reduce the pressure further, and a Magnahelic differential pressure meter, which is what gives the unit its name. The Magnahelic is set up to read 8 with the end of the tube open, and ideally should register 0 when the end of the tube is closed. In a whole flute, it's OK to be as bad as 2, but any worse that that is likely to weaken the response. Obviously each pad individually has to be a lot better than 2 if that is to be the whole flute result. The meter is sensitive enough to detect airflow through the whorls of one's fingerprint - you need to wet your fingers before testing a keyless flute. I tried out the Magnahelic on the pads of the concertina I'm looking at at the moment, and found most pads registered around 4. One was much better at around 2, some worse around 6. One even scored an 8 - when I opened the pad, I could see that the seat impression ran right up to the edge of the pad at one point. Enough flow to startle the Magnahelic, but obviously not enough to make the reed vibrate. Now that's possibly not a problem for a high pressure, low flow instrument like the concertina, although it would spell doom for the high flow, low pressure flute. I haven't tried it out on other concertinas, and wondered if anyone has had experience here? Is it just a point of interest, with no practical import? Or should one get obsessive and use such tools in the search for perfection? Terry