This is the follow on story of the sound module project for the Hangar 9 Twin Otter and later on the slightly smaller Nexa Canadian Rescue Twin Otter although it would be quite usable for any twin turbo propped aircraft. To enhance the sound I am using cardboard tubing. The tube is 50mm in diameter and has a wall thickness of 2mm This will not only enhance the lower frequencies but amplify the sound a little bit more.
I discovered by accident a cardboard tube in my hangar which saved me having to buy a pack of 5 from a packaging company. I wanted two 4 inch tubes so I marked the 50mm tube and at the marked lines I dribbled CA Thin which will soak through and harden the tubing. This will when I cut it (hope fully) reduce any furring or de-laminating of the tube. In actual fact it cut quite well. In the video you should be able to hear the difference the "boom tubes" make. Of course there is a compromise. The volume and quality of the sound from light weight speakers. To get more volume would mean a power amplitier of say 12 watts. This would involve heavier speakers and slightly larger too. All the latter would add more weight for the model to carry unless of course you could use it as ballast but that is mostly unlikely.
Updates
The sound effect has been edited in a Digital Audio Editor creating left then right engine start up. At 120 secs the tone changes to give the impression it is now in flight. Also at 7 min 30 secs the prop noise dies and only the hiss of the turbines running down.
The original tubes have been extended using a slightly smaller tube inserted inside to give a total length of 7 inches which enhances the lower frequencies
Anyway I will settle on what I have achieved at present and shortly fix the tubes securely into the fuselage.
