Didgiredoo design, construction, and materials

Americo Borza - 01:43am Oct 2, 1998

Hi,

I'm looking to gain and share information on the design and construction of a good sounding Didgiredoo. Many didgi enthusiasts seem to have a mystical belief that a good sounding instrument can only be made by termites eating out the center of certain Eucaliptus in Australia. It seems to me that human kind may have learned something about intrument making in the last few thousand years that has not yet been passed on to the termite kingdom.

Any thoughts?

I have made a few of PVC which are completely cylindrical. The sound is a bit sterile and very boomy. Thicker PVC (sch 40) tends to sound muffled while thin PVC (120) sounds much more resonant and rich. Apparently the resonant nature of the tube material is an issue (as well as playing technique).

Any thoughts?

I have a CD on which an Aboriginal player plays a traditional Didgi and others play a curved bronze Celtic instrument (name ?) which has the same sort of mouthpiece as a Didgi and is played the same way. The Celtic instrument sounds much less rich and varied in tonality and flexibility. Those of you familiar with both of these instruments may be able to shed some insight on a sensible way to approach the design and construction of a proper didgi (straight, tapered, flaired, material, dimensions, etc.)

Any thoughts?

Those of you that have experience with experimental instruments may be able to share information about the possibility of a tuneable or fingered didgi similar to a trombone or a recorder or perhaps a crumhorn. Ideally for simplicity of construction the instrument should not require a mechanical contrivance or series of levers etc. to get the job done.

Any thoughts?

Thanks


Dan Bruner - 08:20am Oct 2, 1998
Musician/Experimental Builder

Hi Americo,

I have been interested in the "tunable" didj for a while now too. I was looking into two sizes of schedule 40 PVC that would slide into each other, but never got around to working on it. I have the two pieces that I need as well as a general plan, but I couldn't find the propper fitting for a good mouth piece.

I did design a sectional didj last year. The whole idea behind it was portability and the option to change key. Here's the address where I have the plans for it: http://www.shol.com/bruner/didj1.html

A spin-off from this idea was to use the extra tubes to make a "tube drum" It just so hapen's that they sound pretty good when played along with a didj. I have a link to these plans off of the didj link stated above.

I'd like to hear what you think about it. I'm open to all comments and suggestions.


Americo Borza - 12:32pm Oct 2, 1998

Hi Dan,

I have already seen your pages. Very well done. Your info was part of what I studied to get me up to speed.

I am a beginning player and therfore do not have CB down. I have found that a mouthpiece with an ID of from 1 1/4" to 1 1/2" is about ideal for me. This can be done with a 1" PVC coupler. I round the edges and then smooth them with 600 wet-dry paper. No need for a wax ring. This coupler I use on 1" sch 120 PVC ( which is much greater than 1" ID). It provides me the back pressure I need as a beginner and sounds better than the units I have made with 2" PVC. It may be that I do not have the skill necessary to blow 2". But then again maby not. It may be that this combination is serindipidous. Comments?

What diameters and types of pipe have you found that slide together nicely for a slide didgi?

I am not familiar with music theory or the theory of different dia resonant pipes attached to one another, but, intuitively it seems that if one were to make one didgi from a series of continuously larger dia pipes (1", 1 1/4", 1 1/2", and 2") with a coupler between each size, that each section would have its own fundamental resonance and the entire column would have its fundamental resonance as well. By tuning each section's length properly, one could tailor the entire instrument's harmonic structure at will, therby allowing one to "voice" the instrument for personal preference or use. This might also allow the player to hit individual harmonics or resonances during playing and therby make a more versitile instrument. This procedure would also grossly approximate a conical shape and help to produce a more complex tonal pattern with even harmonics included. Also, starting with a small dia pipe, back pressure coul be maintained for easier playing and yet the exit would approach a "bell" for better volume. I have no idea if my intuition is correct and have no idea what musical theory would require of the different lengths for a "melodious" sound. Any ideas?

Also, the idea of a fingered instrument, in which the resonances are excited by vibrating lips, as in a didgi, rather than a reed or a whistle slot seems to hold promise, if possible. I presume size matters. But, with a didgi, the player can produce a huge number of interesting and compelling sounds from what is basically a one note instrument. Imagine what could be done if the range could be increased to perhaps an entire octave? Wow! Any comments or ideas?


Daniel Bingamon - 05:59pm Oct 2, 1998
MIMForum Staff

Have you considered an early instrument such as a Lizard as starting point. I wonder if something similar could be designed using straight pipe instead of tapered. I know it's not the same thing but maybe it might spark an idea.


Americo Borza - 11:35pm Oct 2, 1998

Thanks, for the tip. That is exactly what I had in mind. The fact that it is not straight is not a problem. Would probably have to be bent so as to be able to make the fingering possible. Also, most didgis are really not cylindrical. Especially the better sounding ones. They tend to be slightly conical in shape with at least a small bell exit.

The "Lizard" seems to have a mouthpiece like a trumpet or tuba. But that does not seem insurmountable. The problem I see is that a didgi has a rather large bore (starts about 1.5-2.0" at the mouth and expands to about 2-4" at the exit) and is rather long (about 4.5-5'). Probably about like a big saxiphone strightened out. I intuit that these large dimensions will require very large holes that cannot be covered with fingers alone and probably are so far apart that no human hand can make the spread.

Are there any other sites that address the "Lizard"? Sure would be nice to see a bass version and information on its dimensions and hole locations.

Is there a way to get some persons that are familiar with design and theory to view this thread? I suspect most subscribers to this site do not view a Didgi as a musical instrument. My research of the archives shows not one reference to Didgis.

Thanks

ab


sysop - 08:27am Oct 3, 1998
Deb Suran

There is one archived discussion on didgeridoos -- scoll down the catalog page under "Woodwind Instruments" -- you probably searched using an alternative spelling.


Thomas Hastay - 05:34pm Oct 4, 1998
Amateur instrument maker/engineer/multi-instrumentalist/Celtic buff

Hi gang.

Americo,see post #2 under "Serpents".I left measurements there for a tenor cornett(serpent).

My thoughts on didj's are thus; Mathematic theory for a didj in contrabass "C" would be approx. 76inches long and have a bore expanding from 1.5inches to 5.5inches. This is based in part on a didj being a "closed pipe" instrument with similar characteristics to a clarinet( a didj uses lips instead of a reed). A clarinet plays 1/3 to 1/4 lower in tone to a flute of the same bore length and it's length approximately 45 times it's bore diameter.

A didj 76inches long would have a bore diameter of approximately 3.5inches and this is to large for a comfortable mouthpiece,so to decrease the mouthpiece to 1.5inches you must increase the bore end to 5.5inches to keep the same 1/2 frequency wavelength.

Because the didj plays 1/3 lower(closed pipe theory) you must solve for a wavelength frequency for "F"(87.285hz) above contrabass "C"(2 octaves below mid C)and it will have a fundamental frequency of contrabass "C" (65.395hz) because it plays a third lower in pitch.

Changing the tonal harmonics can be done by flaring the bore end into a bell for loud brassy tone like a fanfare trumpet or pinching the bore end into a bulb like an oboe for mellow tone or creating a "standing wave" of back pressure by capping the end and placing the bore end hole on the side.This last method is done by aborigine's by using the root ball of the gum tree for a hollow resonator and placing the hole on the side close to the bottom.

In my opinion,most musical instruments resonate beter if they are made from dense/resinous hardwoods and improve with age because this resin crystalizes over time improving harmonic tone.Metalic structure is crystal as well. An historical note would be the bridges of ancient lyres being made of amber(crystalized tree sap).

This is all my own theory and conjecture based on a little math and history,so please feel free to offer your opinions and critique mine. I respect all of your opininions.

Thomas.

P.S. The Celtic horn you spoke of is called a Carnyx and was used in warfare to scare the enemy. The head of this horn was usualy a boar or horse.


Americo Borza - 11:58pm Oct 4, 1998

Deb,

Thanks for the info. I finally got to the archive list and found the Didgi postings.

Thomas,

Thanks for the posts on both threads. I appreciate the consideration.

I cannot tell you how good it feels for a newbie to a list to be asked for opinions and critique. It is a singular experience! In keeping with the request, I will do so with the intent of learning something. Pardon me if I make newbie errors but learning is a bumpy road.

If my memory serves me, in instruments of the same length, a flute (cylindrical and effectively open at both ends) has a higher fundamental than a clarinet (cylindrical with a flair and open at one end only). Also, in instruments of the same length, a sax (conical and open at one end only) will have a higher fundamental than a clarinet (cylindrical with a flair and open at one end only). I have not read about the relationship between a flute and a sax of the same length. Therfore, I do not know which will contribute more to a higher fundamental, two openings, or a conical bore.

If I did not misunderstand what I have read, its an apple and oranges problem. I also understand that didgi players say of two didgis with the same length and one being of conical taper and the other being cylindrical, that the cyl goes lower but the conic has much better overtones with a higher fundamental. I understand that the conical shape results in even and odd harmonic production whereas the cyl shape only produces odd harmonics. I am not being argumentative. I am pointing out what seems to be an incongruity between what I have read and the math and conclusions in your paragraphs 2,3 and 4. Am I in error? Please explain.

I like the idea of experimenting with a blocked exit with a hole in it. Of course the hole need not be in the side. It could be in the end. My understanding is that the maximum acoustic impedance (back pressure ?) occurs as a result of resonance and harmonics at he resonant and harmonic frequencies. Aside from those points, back pressure would be little affected by a block unless the hole was so small as to limit the passage of air. This matter is of great concern to didgi design because without sufficient back pressure it is almost impossible to successfully maintain a drone by circular breathing and with too much, the instrument becomes impossible to blow.

Didgi players seem to think that having a relatively small dia bore for some distance from the mouth piece increases back pressure (perhaps due to fluid resistance along the walls of the bore). Then the bore should become more conical to the end. Any ideas or clarifications?

BTW where have you seen Aboriginals play didgis with a hollow resonator at the end of a didgi? I have seen many photos of a variety of didgis and none were like that. Although some (reported to be loud playing) had very substantial bells that seeme to close in on themselves somewhat.

In regard to "better" wood resonance I must say that my best project was a copy of a Hauser small body classical guitar. In researching for that project I examined many woods and did a great amount of study. That coupled with the fact that I have friends that are professional luthiers making violins, etc. for the world market, leads me to the following.

The term "better" in describing resonance is confusing. Perhaps "proper" is a more useful term. Then, after determining the "proper" woods for the purpose, the "better" or "best" ones can be chosen. Anyone who has tapped a spruce sound board and a rosewood back for tone has discovered that they do not sound the same. But which is "better"? For what purpose? I would not use rosewood as a soundboard simply because it has a higher resin content and is harder. I suggest that a wood to be used for a given purpose should be the one that is proper for the purpose. Very hard woods should be used for "click stick" type instruments for their durability and ringing quality. I would not use a cedar tone wood for that purpose. It would not be the "proper" wood no matter how "good" a tone wood it was. It would sound awful and quickly wear as well.

I understand that Didgis made of very hard woods exhibit the best sonic qualities. Whereas some wind instruments are made of box wood, which is quite soft, but, very stable, easy to work and in use creates the desired or traditional sound that is sought after. In the second case, box wood, though softer and non-resinous, is "proper" and therfore selections can be made to get the "better" or "best" piece to use.

As for resins in the wood, some observations. My luthier friends use a variety of woods for their instruments. Some very old air dried, some less old air dried and some young kiln dried. While they suspect that there are some ongoing chemical changes in the wood over time, they find that "proper" old wood is "better" because of its original quality not because of hardened resin. The grain is tighter and more uniform, and figure is better. Very high quality young wood is not really available and excellent old wood is getting very scarce and very expensive. However, should they find "better" young wood than the old that is available, they use it. So crystalization of resin is not really the issue. Of course this all presumes proper drying and stability.

I suspect that as an engineer you are pulling my leg a bit in regard to the "crystal" question. If amber has qualities that cannot be replicated in the modern world for use as bridges, then so be it. But I suspect that modern materials exist than can suitably replace it from a sonic perspective. Plastics were not available back then and today we ascribe no magical qualities to amber. However, it could still be used for its historical authenticity.

To suggest that the sonic qualities of instruments are significantly contolled by the common characteristics of the crystalline structures of resins in wood, of amber and of metal is more than can be handled in this post. If you so desire we can continue that thought off this list so as to save the list space.

Whew! This is work. But it makes you think.

BTW is it fair to say that if I extended the OA length of the instrument you described, that placement of the finger holes and internal dimensions could be determined by ratio and proportion? How about hole diameter? I am thinking of a didgi about 5-6 fee long. Any thoughts?

Thanks for the help.

ab


Americo Borza - 12:17am Oct 5, 1998

Hello Thomas,

I forgot to address your P.S.

I have a CD called "Reconcilliation". The lead player is one Simon O'Dwyer. He specializes in traditional Cetic music. He plays all brass copies of instruments he calls the Dord Iseal (bass), the Dord Ard (mid range) and the Adhare (hi freq). These are the instruments I described in a prior post.

They are played in the same manner as a Didgi, are limited to 3 notes (no fingering at all) and do not sound as good as the Didgi played on the same disk. By as good I mean they do not produce the same sort of varied sounds and range as the didgi. In essence they sound like a rough three note tuba. Are these the same instruments you call the Carnyx?

Thanks


sysop - 07:11am Oct 5, 1998
Deb Suran

some wind instruments are made of box wood, which is quite soft
Boxwood (Buxus sempervirens) is actually a very hard wood with a close, even grain; which is why it is favored for both woodwinds and stringed-instrument tuning pegs.


Jens Wendel - 01:03pm Oct 5, 1998

Deb, you are right! I want to add that boxwood tends to warp, I made a bombarde some years ago wich is pretty crooked now and a friend of mine has a set of uillean pipes made of boxwood- the drones look like a bunch of flowers :) .

Very expensive, and hard to get. I think you can't find a piece big enough for a didge.


Americo Borza - 06:13pm Oct 5, 1998

Deb,

I thought the road would be bumpy. I confused box wood with bass wood. Big difference. But, if woodwinds have a significant contribution to their traditional sound by virtue of the wood used (like the violin family), then the point is made. If not, then they could be made of a specifically engineered plastic and cast at rather low cost. Somehow I don't think that will happen soon.

In the ongoing search to answer some of my questions, I have found the following urls that may be of use to some in this group:

http://www.phys.unsw.edu.au/music/pipes.html

http://www.phys.unsw.edu.au/music/woodwind.html

http:/ccrma-www.stanford.edu/~jos/jos-mohonk-book/node25.html

Enjoy!

ab


sysop - 07:28pm Oct 5, 1998
Deb Suran

If not, then they could be made of a specifically engineered plastic and cast at rather low cost. Somehow I don't think that will happen soon.
It's already happened, I'm afraid -- plastic recorders. I don't think anyone here is saying that materials don't affect the sound, but that it's OK to use non-traditional materials, especially if you're not expert musician enough to take advantage of the nuances afforded by traditional materials. Like me with a plastic recorder <g>.

Pipes and Harmonics
How Do Woodwind Instruments Work? both by Joe Wolfe

Single-Reed Instruments


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