Thursday, March 26, 2009

Material procurement

As mentioned before, PVC tubing was the selected material for the project. Now it was necessary to define the proper internal diameter. The bore diameter of a Bb soprano clarinet is about 14mm and for a Bb bass clarinet is about 24mm.

In some notes "On scaling a woodwind to a new pitch" by the
physicist and acoustician Arthur H. Benade, some criteria are discussed to scale a woodwind while preserving the sound color. Without entering intricate details it can be said that it is necessary to preserve the effective shape of the air column, since it will define the local characteristic impedance. It can be shown that if the ratio of pitches is phi = f new / f old, the area ratio is equal to the ratio of pitches and then the equation to scale the bore diameter is d new = d old / (phi)^2. In our case the ratio of pitches is 1/2, since the new instrument will sound an octave lower. Therefore, starting from 14mm for soprano clarinet, we get 19.8mm for bass and 28mm for contrabass. Well, we start to notice some divergence between the fundaments of physical scaling and the practical acoustic behavior. Woodwinds acoustics is, after all, a grey zone between science, craft and art.

However, after some research I discovered that Leblanc contrabass clarinets have a bore of 30mm and Selmer a bore of 34mm. On the other hand Eppelsheim c
laims that his instrument features "wide bore for a warm, voluminous tone".
Now we come to a remarkable advantage of USA re
tail shops: infinite options are available. If this supposes in many cases a real added value, is a matter of discussion, but in this case this feature proved invaluable. If you want to buy milk, there is with 1.2% fat, 1.5%, 2%, and all the way up in incredibly small steps. There is a choice of added vitamins for every alphabet letter, iron added , potasium added, you name it. In Europe options are kept within more reasonable limits.

I noticed that a PVC pipe of 1-1/4 inch schedule 40, having an inner diameter of 34mm, would be ideal for the job. Schedule 40 refers to the thicker tube wall, which for this diameter is about 4mm thick. Luckily, my brother was travelling to USA and I prepared my shopping list as follows:
- 1x PVC tubing Schedule 40/DWV 1.25 In. 10 Ft.

- 6x 1-1/4 In.
PVC Schedule 40, 90 Degree Elbow Slip x Slip
- 2x 1-1/4 In. PVC Schedule 40, 45 Degree Elbow Slip x Slip

- 2x 1-1/4 In. PVC Coupling, schedule 40, slip

Here is the bill from Home Depot for a total amount of $10.99.

And here is the material, that travelled some 10'000km just for this project.


  1. I was looking for the same. Glad to read this blog.Thanks for sharing.

    San Mateo Plumber

  2. Thanks for the sensible critique. Me & my neighbor were just preparing to do some research about this. We got a grab a book from our local library but I think I learned more clear from this post.
    San Francisco Plumbers