Introduction to engine sounds for scale electric models

Fitting generated engine sounds to electric model aircraft is a new exciting concept and it is constantly being improved.
How does it work?

By adding the TBS Mini electronic circuitry and conventional loudspeakers to the model, the genuine full size engine sound is emitted from the model. The engine sound speed is proportional to the throttle position and thus coordinated with the speed of the electric motor and propeller. It brings the model alive and transforms it to give the impression of a full size plane in the air. This gives a whole new reality to scale model aircraft especially in flybys when the ‘Doppler’ effect is apparent. Audible gun firing is easily possible using an auxiliary channel on the transmitter which is great fun in dogfights. The full stop/start sequence is also provided to add to the model’s realism. The circuitry can be used on single and multi-engine aircraft.
Weight

The first thing to consider is the payload that your model can carry. This will determine the system you use and the number of speakers. This also sets the sound power output. The lightest system is 8 oz. Total including speaker. The sound can appear very loud on test, but will dissipate in flight. We achieve 98dba @ 1m with the 8-oz. Single speaker system and 102dba with a 32oz. Dual speaker system. This is quieter than a normal I/C engine but very realistic, and probably a ‘scale’ sound level! The speakers can be fitted into the cowl or underneath the fuselage or wing. They need to be installed in a sound box of sorts, and have a grill to stop the propeller air from blowing the speaker cone back into the speaker. Design the speaker installation so that the speaker(s) can be changed, as they are run at their maximum output and can fail.
Electronics

The electronics consist of the Benedini TBS Mini sound circuit which have pre-programmed engine sounds. Select from the list of engine types. Try and select an engine type that is appropriate for your type of aircraft. The small TBS Mini circuit is plugged into the receiver throttle channel and the engine sound is proportional to the throttle stick setting. A full engine start/stop sequence is also pre-programmed into the sound file. Also all military aircraft type engine sound files contain an optional machine gun sound that can be controlled from a separate channel.The power for the TBS Mini is supplied from the receiver and the current draw is very small (less than a standard servo).
Amplifiers

The other Benedini circuit you will need is the amplifier. This is connected between the TBS Mini and the speaker(s). The power source can be from the flight battery or its own battery.
There are two amplifiers to choose from

2 x 40 watt amplifier. This runs on anything from a 3s lipo pack (11.1v) to 18 volts. The amplifier has two independent outputs and will drive two speakers, but one may be used if required. It has in integral volume control for volume adjustment. It is more than powerful enough to drive two speakers beyond their capacity, so we recommend caution when adjusting.

50V amplifier This is like the 2 x 40-watt amp but will run on higher voltage so it is best to select the amp most suited to run on the main flight pack.
Interference

We have tested the electronics very carefully on the ground and in the air. To date their have been no interference problems using good wiring practices. A ferrite ring can be fitted to the receiver throttle lead as a precaution.
Ordering

Add a TBS Mini sound module to your order. You need to decide on the amplifier based on your flight battery or power supply. Then determine to purchase two speakers or one. Choose an engine sound that will be pre-programmed into your TBS Mini. Full setup instructions are supplied with the TBS Mini and the amplifiers.   Don’t forget to let us see and hear your project so we can add a link!