Square contra bass clarinet experiments

The idea was born when I saw the plywood contra bass recorders made by Joachim Paetzold. (see https://youtu.be/tbUKilNdg40) I wondered if it would be possible to make a contra bass clarinet like that. So I started a few experiments.

Experiment 1: The Plywood wooden tube with 180 degrees turn

The first experiment was too optimistic. A wooden tube was build with an straight 180 degrees turn. I mounted the mouthpiece and the tube with the receiver of an Vito Leblanc contra bass clarinet in a round hole made in the square tube,

It did not work at all. What could be the cause of that? Of course I closed all the leaks with hot melt glue. I wondered if this was an effect o the tube being a square. But I can't imagine that. The contra bass recoreder uses square tubes and pipe organs have square tubes too.

The experimental tube was modified by adding roughly rounded corners to the turn. That did not have any effect.

Other possiblities: the construction is too rough. The inside of the tube should be smoother.

Experiment 2: round pvc tubes 

The next experiment was with pvc tubes.

The first part of the experiment was done with a cheap straight 12mm tube with the end thickened up with duke tape to interface with a standard bass clarinet mouthpiece. The innerdiameter of the tube is much smaller than the mouthpiece. But it works without any problem.

The next part was done with a larger pvc tube with rounded corners made of 90 degrees turns. The interface between the mouthpiece and the tube was made by molding plastic. This version was also working. It was not perfect but with some effort I was able to play a low 36Hz tone with the installation.

Still leaks caused by too loose mounted turns are a problem.

Also I found out that very low notes vibrate at a very very low frequency. That is what I know from the commercial contra bass clarinets. I had the idea that the effect is stronger when the diameter of the pipe is smaller.

Experiment 3: interfacing the square tube

The interface between the round tube of the receiver and the square of the wooden tube could be the problem. So I design a interface tube and produced it with my 3D printer. The inside is a gradual transition from round to square. I screwed it on the top of the square tube with a rubber strip in between. It did not work ;-(.

I starte

d to doubt if square is even possible or that square tubes are very sensitive for being smooth.

I contacted a builder of pipe organs to ask among others if the diameter and the inside of the tube are very critical. 

The first answers were that the tubes diameter is important but not very critical. The roughness is not important. In some organpipes raw clothes are used and others are smoothed by glass. 

Experiment 4: aluminium square tube

The fourth experiment was a standard product of 25mm square aluminium tube connected to the (modified) 3D interface.

This was a succesfull and intersting experiment. The tube could even be extended with a part of the square wooded tube and produced a nice 40Hz tone. But what also was found is that a minimal shift of inner square of the interface relative to he inner square of the other tube (the aluminium or the wooden) has a large effect. The tube does not sound.

So what is clear now:

• a square tube can play
• the interface is important
• irregularities in the tube must be prevented in the first part of the tube
• a large diameter is better or low tones 

The next step will be an experiment to make a wooden turn with a square diameter that is smooth enough to allow a tone to be produced.

Experiment 5: 3D printed interfaces

The purpose of the next experiment was to make a good interface from the mouthpiece to a square shaped tube.

I build a 2m long wooden tube with inner diameter of 26x26mm. The upper 20mm of the tube is round to 40mm diameter and provided with 1mm o cork to be able to make a good connection to the interface. The interface was designed to be 3D printed in two half curves of 90 degrees. One connects to the wooden tube and the other aluminium tube.

All together it resulted in a over 2m long bass clarinet. At first it did not play. It appeared to have leaks. After all the leaks were fixed with hot melting glue it sound strong with a low 34 Hz tone. That is almost low C. The only point is that is vibrates strong. This is a known problem with very low notes. Pipe organs suffer from the same problem.

Experiment 6: toneholes

The next experiment will be to measure the position of the toneholes and see what a higher tone does with the sound quality.

In the mean while I will try to find some experts to ask their opinion about the vibrations.