The loudspeaker converts electrical signals into differentiated sounds. Depending on the task, loudspeakers are designed for a specific frequency spectrum. A full-range speaker, for example, has a spectrum of 40-20,000Hz. Loudspeakers may only be operated with appropriate power and the correct resistance value. If the control is too strong, the speaker will be destroyed. If the control is too high impedance, it can be destroyed by the lower internal resistance or the increased current flow of the loudspeaker. The formula applies to our speaker: ?(P*R)=U,?(0.25W*8?)=2V. Therefore, the speaker must never be connected directly to our 9V power supply