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 Post subject: inside shape (air column)
PostPosted: 26.02.2007, 11:42 
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Joined: 24.02.2007, 00:24
Posts: 189
Location: France
Hi there !

I've made some small sketches of different air column shapes.
Divided the tube in 3 segments.

Image

Image

Could you please tell me the caracteristics of each of them ?

I already know that the first 1/3rd determines backpressure (thin=highBP, large=lowBP).
That the last 1/3rd (bell) determines the volume of the sound (largeBell=StrongSound).
That the air volume (shape determined by its lenth and thickness' variations) determines the tune (easy to calculate in conic shapes, but not-so-easy in weirder shapes).

How does thickness of surrounding wood influence the sound ?
Do inside cavities change anything positively, or do they spoil the sound ?
etc...

Could you also tell me to which one a Yidaki looks like, and to which other one a Mago looks like ?

Thanks for your answers :D


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PostPosted: 26.02.2007, 13:12 
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Joined: 18.03.2006, 21:53
Posts: 789
Don't want much do you? :wink: :lol:

Looks like you need to get a copy of the didgeridu phenomenon and look at Ben Hicks site http://www.hickssticks.com/making_didges.html

and...
http://www.didgeridoo-physics.com/E/index.htm
http://www.navaching.com/shaku/didge.html
http://www.yedaki.de/main/trilobyte/SW_BAU_STEP1.HTM

Kev


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 Post subject:
PostPosted: 26.02.2007, 13:13 
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Joined: 10.04.2006, 18:51
Posts: 141
Location: Italy
i'd say E1-> mago and E3/D-> yidaki

_________________
we're just dust...


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PostPosted: 26.02.2007, 13:50 
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Joined: 24.02.2007, 00:24
Posts: 189
Location: France
LongDog > Thanks for the links... I'll check on them !
Saldali > thanks for the answer !

:wink:


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 Post subject: Re: inside shape (air column)
PostPosted: 27.02.2007, 21:11 
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Joined: 22.03.2006, 20:18
Posts: 195
Location: California USA
Greetings Ahaw,
It's just my opinion of course, but I don't agree with everything you have said.
Ahaw wrote:
I already know that the first 1/3rd determines backpressure (thin=highBP, large=lowBP).

Yes, the bore of the first 1/3 can have a large affect on back pressure, but back pressure is essentially a result of the standing wave generated when the complete didj vibrates at it's resonant frequency.
Try to blow (no lip vibration) through a small bore didj, then try to blow trough a big bore didj....not much difference is there? They both offer very little resistance to air flow.
Restriction of airflow due to bore diameter is insignificant when discussing back pressure.
Quote:
That the last 1/3rd (bell) determines the volume of the sound (largeBell=StrongSound).

I'll agree with this, although I'll add that large bell also usually means higher pitch for the length.
Quote:
That the air volume (shape determined by its lenth and thickness' variations) determines the tune (easy to calculate in conic shapes, but not-so-easy in weirder shapes).

Definately more difficult in irregular shapes.....I'd stay away from actual conical, that doesn't really make a very good didj in my experience.
Quote:
How does thickness of surrounding wood influence the sound ?

Ten different didj players/craftsmen will give you ten different answers to this question. Mine is "I'm not sure exactly"
Quote:
Do inside cavities change anything positively, or do they spoil the sound ?
etc...

Inside cavities can be good or bad. Sometimes an inside cavity can result in a desireable "singing tone" which in the right place is quite nice. Or if in the wrong place can be disharmonious.
Quote:
Could you also tell me to which one a Yidaki looks like, and to which other one a Mago looks like ?

I don't think that any of the shapes look like a typical yidaki or mago.
Too much pure, straight conical taper for a yidaki, not open/straight enough for a mago.

I would follow Longdogs suggestion and get the book "Didgeridoo Phenomenon" or acces the info on the web by the same authors of the chapter on didj physics to learn more about the affect bore shape has. And you don't have to limit yourself to info regarding judt didgeridoo....people have been studying accoustical physics as relates to a closed end vibrating air column for centuries....it's pretty much appropriately applied to a didgeridoo also.

Like I said, this is just my opinion based on my experience, your milage may vary.
I welcome others views.
hope this helps.
namaste,
kellymon


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 Post subject:
PostPosted: 27.02.2007, 22:24 
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Joined: 18.03.2006, 00:50
Posts: 750
Location: Canada
Hi there

Trust me Robert knows his stuff . :wink: passionate and good crafter .I own one of his .

GGW


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 Post subject:
PostPosted: 27.02.2007, 22:52 
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Joined: 24.02.2007, 00:24
Posts: 189
Location: France
KellyMoon = Robert ?
Well thanks KM for all the infos !
Lots of interresting stuff here !
(and thanks for the greetings too!)


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 Post subject:
PostPosted: 28.02.2007, 00:17 
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Joined: 18.03.2006, 00:50
Posts: 750
Location: Canada
Hi there

Yep Kellymon not Moon ! Moon is somebody else, a freind of Kellymon ,Moondrop is a freind of mine too , right Robert ? :lol:
Oui Ahaw il y as beaucoup de bon stuff ici :wink:

GGW


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 Post subject:
PostPosted: 28.02.2007, 01:23 
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Joined: 22.03.2006, 20:18
Posts: 195
Location: California USA
GGW,
Thanks for your kind words, my friend :) Do you still play that "flat of F" stick? Knowing more about your preferences now, I might have done a few small things different....
Yes, Moon is a real friend :)
Is it possible we will see you in California this August?
namaste,
robert


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 Post subject:
PostPosted: 28.02.2007, 13:11 
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Joined: 18.03.2006, 00:50
Posts: 750
Location: Canada
Hi there

Oh! for sure i still play that stick .I like all kind of didge with different construction and playabality.I like to give this didge a ride when i can he play so loud !
I send Moon a mail about getting to Jt's and no answer yet .

cheers
GGW


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